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A S Lichter

Publications and source records attributed to A S Lichter.

At least 19 recordsLinked to original sources
PubMed1998

The impact of treatment complexity and computer-control delivery technology on treatment delivery errors.

PURPOSE: To analyze treatment delivery errors for three-dimensional (3D) conformal therapy performed at various levels of treatment delivery automation and complexity, ranging from manual field setup to virtually complete computer-controlled treatment delivery using a computer-controlled conformal radiotherapy system (CCRS). METHODS AND MATERIALS: All treatment delivery errors which occurred in our department during a 15-month period were analyzed. Approximately 34,000 treatment sessions (114,000 individual treatment segments [ports]) on four treatment machines were studied. All treatment delivery errors logged by treatment therapists or quality assurance reviews (152 in all) were analyzed. Machines "M1" and "M2" were operated in a standard manual setup mode, with no record and verify system (R/V). MLC machines "M3" and "M4" treated patients under the control of the CCRS system, which (1) downloads the treatment delivery plan from the planning system; (2) performs some (or all) of the machine set up and treatment delivery for each field; (3) monitors treatment delivery; (4) records all treatment parameters; and (5) notes exceptions to the electronically-prescribed plan. Complete external computer control is not available on M3; therefore, it uses as many CCRS features as possible, while M4 operates completely under CCRS control and performs semi-automated and automated multi-segment intensity modulated treatments. Analysis of treatment complexity was based on numbers of fields, individual segments, nonaxial and noncoplanar plans, multisegment intensity modulation, and pseudoisocentric treatments studied for a 6-month period (505 patients) concurrent with the period in which the delivery errors were obtained. Treatment delivery time was obtained from the computerized scheduling system (for manual treatments) or from CCRS system logs. Treatment therapists rotate among the machines; therefore, this analysis does not depend on fixed therapist staff on particular machines. RESULTS: The overall reported error rate (all treatments, machines) was 0.13% per segment, or 0.44% per treatment session. The rate (per machine) depended on automation and plan complexity. The error rates per segment for machines M1 through M4 were 0.16%, 0.27%, 0.12%, 0.05%, respectively, while plan complexity increased from M1 up to machine M4. Machine M4 (the most complex plans and automation) had the lowest error rate. The error rate decreased with increasing automation in spite of increasing plan complexity, while for the manual machines, the error rate increased with complexity. Note that the real error rates on the two manual machines are likely to be higher than shown here (due to unnoticed and/or unreported errors), while (particularly on M4) virtually all random treatment delivery errors were noted by the CCRS system and related QA checks (including routine checks of machine and table readouts for each treatment). Treatment delivery times averaged from 14 min to 23 min per plan, and depended on the number of segments/plan, although this analysis is complicated by other factors. CONCLUSION: Use of a sophisticated computer-controlled delivery system for routine patient treatments with complex 3D conformal plans has led to a decrease in treatment delivery errors, while at the same time allowing delivery of increasingly complex and sophisticated conformal plans with little increase in treatment time. With renewed vigilance for the possibility of systematic problems, it is clear that use of complete and integrated computer-controlled delivery systems can provide improvements in treatment delivery, since more complex plans can be delivered with fewer errors, and without increasing treatment time.

Humans↗
PubMed1998

Radiation pneumonitis as a function of mean lung dose: an analysis of pooled data of 540 patients.

PURPOSE: To determine the relation between the incidence of radiation pneumonitis and the three-dimensional dose distribution in the lung. METHODS AND MATERIALS: In five institutions, the incidence of radiation pneumonitis was evaluated in 540 patients. The patients were divided into two groups: a Lung group, consisting of 399 patients with lung cancer and 1 esophagus cancer patient and a Lymph./Breast group with 78 patients treated for malignant lymphoma, 59 for breast cancer, and 3 for other tumor types. The dose per fraction varied between 1.0 and 2.7 Gy and the prescribed total dose between 20 and 92 Gy. Three-dimensional dose calculations were performed with tissue density inhomogeneity correction. The physical dose distribution was converted into the biologically equivalent dose distribution given in fractions of 2 Gy, the normalized total dose (NTD) distribution, by using the linear quadratic model with an alpha/beta ratio of 2.5 and 3.0 Gy. Dose-volume histograms (DVHs) were calculated considering both lungs as one organ and from these DVHs the mean (biological) lung dose, NTDmean, was obtained. Radiation pneumonitis was scored as a complication when the pneumonitis grade was grade 2 (steroids needed for medical treatment) or higher. For statistical analysis the conventional normal tissue complication probability (NTCP) model of Lyman (with n=1) was applied along with an institutional-dependent offset parameter to account for systematic differences in scoring patients at different institutions. RESULTS: The mean lung dose, NTDmean, ranged from 0 to 34 Gy and 73 of the 540 patients experienced pneumonitis, grade 2 or higher. In all centers, an increasing pneumonitis rate was observed with increasing NTDmean. The data were fitted to the Lyman model with NTD50=31.8 Gy and m=0.43, assuming that for all patients the same parameter values could be used. However, in the low dose range at an NTDmean between 4 and 16 Gy, the observed pneumonitis incidence in the Lung group (10%) was significantly (p=0.02) higher than in the Lymph./Breast group (1.4%). Moreover, between the Lung groups of different institutions, also significant (p=0.04) differences were present: for centers 2, 3, and 4, the pneumonitis incidence was about 13%, whereas for center 5 only 3%. Explicitly accounting for these differences by adding center-dependent offset values for the Lung group, improved the data fit significantly (p < 10(-5)) with NTD50=30.5+/-1.4 Gy and m=0.30+/-0.02 (+/-1 SE) for all patients, and an offset of 0-11% for the Lung group, depending on the center. CONCLUSIONS: The mean lung dose, NTDmean, is relatively easy to calculate, and is a useful predictor of the risk of radiation pneumonitis. The observed dose-effect relation between the NTDmean and the incidence of radiation pneumonitis, based on a large clinical data set, might be of value in dose-escalating studies for lung cancer. The validity of the obtained dose-effect relation will have to be tested in future studies, regarding the influence of confounding factors and dose distributions different from the ones in this study.

Dose-Response Relationship, Radiation↗
PubMed1998

A brain tumor dose escalation protocol based on effective dose equivalence to prior experience.

PURPOSE: The current study describes the design of a dose escalation protocol for conformal irradiation of primary brain tumors that preserves the safe experience of a previous, sequential dose escalation scheme while enabling the delivery of substantially higher effective doses to a central target volume. METHODS AND MATERIALS: Normalized isoeffective composite dose distributions were formed for 20 patients treated on the original protocol (which specified three progressively smaller planning target volumes [PTVs]) using the linear quadratic model (here corrected to equivalent 2 Gy fractions using alpha/beta=10 Gy). These distributions were investigated and a new protocol was designed to preserve a similar level of efficacy and lack of toxicity for the outer volumes, but allowing a higher dose to the inner PTV. Treatment plans were then investigated to determine if the objectives of the new protocol were achievable. In particular, plans that simultaneously achieved all biological treatment planning objectives (all fields treated each day) were investigated. Finally, the success of the protocol design was demonstrated by analysis of the effective dose distributions of 10 patients treated using the new protocol. RESULTS: The composite normalized isoeffective minimum doses to the outer PTVs (PTV3 and PTV2) in the original protocol were close to 60 Gy and 75 Gy, respectively, and these values are specified as the minimum doses to those volumes for the new protocol. Homogeneity requirements to maintain equivalence for the outer target volume domains are: not more than 25% of [PTV3 exclusive of PTV2] >75 Gy; and not more than 50% of [PTV2 exclusive of PTV1] >85 Gy. Treatment plans using multiple noncoplanar arrangements of beams and static intensity modulation treat all volumes at each session. DVHs of the normalized isoeffective dose distributions reveal the equivalence of the new protocol plans to the sequential plans in the previous protocol as well as the ability to achieve a higher dose of 90 Gy to the isocenter of PTV1 (+/-5% homogeneity required). CONCLUSION: The ability to incorporate past experience through use of the linear quadratic model in the design of a new dose escalation protocol is demonstrated.

Brain Neoplasms↗
PubMed1998

Comprehensive irradiation of head and neck cancer using conformal multisegmental fields: assessment of target coverage and noninvolved tissue sparing.

PURPOSE: Conformal treatment using static multisegmental intensity modulation was developed for patients requiring comprehensive irradiation for head and neck cancer. The major aim is sparing major salivary gland function while adequately treating the targets. To assess the adequacy of the conformal plans regarding target coverage and dose homogeneity, they were compared with standard irradiation plans. METHODS AND MATERIALS: Fifteen patients with stage III/IV head and neck cancer requiring comprehensive, bilateral neck irradiation participated in this study. CT-based treatment plans included five to six nonopposed fields, each having two to four in-field segments. Fields and segments were devised using beam's eye views of the planning target volumes (PTVs), noninvolved organs, and isodose surfaces, to achieve homogeneous dose distribution that encompassed the targets and spared major salivary gland tissue. For comparison, standard three-field radiation plans were devised retrospectively for each patient, with the same CT-derived targets used for the clinical (conformal) plans. Saliva flow rates from each major salivary gland were measured before and periodically after treatment. RESULTS: On average, the minimal dose to the primary PTVs in the conformal plans [95.2% of the prescribed dose, standard deviation (SD) 4%] was higher than in the standard plans (91%, SD 7%; p = 0.02), and target volumes receiving <95% or <90% of the prescribed dose were smaller in the conformal plans (p = 0.004 and 0.02, respectively). Similar advantages of the conformal plans compared to standard plans were found in ipsilateral jugular nodes PTV coverage. The reason for underdosing in the standard treatment plans was primarily failure of electron beams to fully encompass targets. No significant differences were found in contralateral jugular or posterior neck nodes coverage. The minimal dose to the retropharyngeal nodes was higher in the standard plans. However, all conformal plans achieved the planning goal of delivering 50 Gy to these nodes. In the conformal plans, the magnitude and volumes of high doses in noninvolved tissue were significantly reduced. The main reasons for hot spots in the standard plans (whose dose calculations included missing tissue compensators) were photon/electron match line inhomogeneities, which were avoided in the conformal plans. The mean doses to all the major salivary glands, notably the contralateral parotid (receiving on average 32% of the prescribed dose, SD 7%) were significantly lower in the conformal plans compared with standard radiation plans. The mean dose to the noninvolved oral cavity tended to be lower in the conformal plans (p = 0.07). One to 3 months after radiation, on average 60% (SD 49%) of the preradiation saliva flow rate was retained in the contralateral parotid glands and 10% (SD 16%) was retained in the submandibular/sublingual glands. CONCLUSIONS: Planning and delivery of comprehensive irradiation for head and neck cancer using static, multisegmental intensity modulation are feasible. Target coverage has not been compromised and dose distributions in noninvolved tissue are favorable compared with standard radiation. Substantial major salivary gland function can be retained.

Carcinoma, Squamous Cell↗
PubMed1998

Radiation following chemotherapy for mediastinal Hodgkin's disease: the outcome of various doses for bulky tumors.

Twenty-one patients with bulky mediastinal disease responding to chemotherapy received consolidation with low-dose mediastinal radiation (19.8-25.2 Gy). Their 5-year mediastinal failure rate (10%) was equivalent to that of 10 similar patients who received higher doses of 30-44 Gy (20%). Low-dose radiation may be appropriate for these patients. Prospective studies are required to verify these findings.

Adolescent↗
PubMed1998

Spinal cord dose from standard head and neck irradiation: implications for three-dimensional treatment planning.

BACKGROUND AND PURPOSE: Treatment with traditional standard field arrangements for patients with head and neck cancer rarely causes myelopathy. Often, initial treatment fields are reduced to avoid the spinal cord after 45 Gy has been delivered and the cord dose that is delivered by 'off-cord' fields is not calculated. To determine a conservative limit to set for the cord dose for conformally-planned field arrangements, the total spinal cord dose delivered with standard opposed lateral fields was evaluated. MATERIALS AND METHODS: Two types of treatment plans were evaluated for 10 patients enrolled on a parotid-sparing protocol for bilateral head and neck treatment, i.e. (1) standard opposed lateral fields, including large initial fields treating nodal volumes to 45 Gy, off-cord fields for an additional 25 Gy and electron nodal boost fields for an additional 5 Gy and (2) complex 3-D treatment planned field geometries with conformal dose distributions (actual treatment fields). Treatment fields for the protocol conformal plans were arranged so that the maximum cord dose was not to exceed 50 Gy. Dose-volume histograms for both types of planned treatments were analyzed. The maximum and minimum dose to the 1 cm3 cord volume receiving the highest dose were reported. RESULTS: The maximum dose to the cord from the standard composite plans was on average 52 Gy, with a range of 48.9-55.9 Gy. This consisted of an additional 6.3 Gy (average) from the scatter and block transmission dose from the off-cord lateral fields above the prescribed 45 Gy. For the conformal plans, the maximum dose was on average 49.4 Gy (which is protocol criteria). DISCUSSION AND CONCLUSION: The maximum spinal cord dose of 50 Gy set as a dose constraint for 3-D treatment planning for conformal plans is a comparable dose to that given in standard opposed lateral head and neck treatments and has been determined to be a conservative spinal cord dose limit, which we have applied in our clinic.

Head and Neck Neoplasms↗
PubMed1998

Immunolymphoscintigraphy in breast cancer: evaluation using 131I-labeled monoclonal antibody B72.3.

Noninvasive axillary lymph node staging was investigated using [131I]murine monoclonal antibody B72.3 in 16 patients with breast cancer scheduled for axillary dissection. [131I]B72.3 was injected into ipsilateral finger webs or around the breast biopsy. Scintigraphy to 72 h and gamma-counting/immunohistochemistry of nodes were performed. Specific antibody uptake (%ID/g) and the ratio of specific:nonspecific antibody uptake were not significantly different in tumor-positive versus tumor-negative nodes, suggesting that [131I]B72.3 is unsuitable to discriminate axillary node tumor involvement.

Antibodies, Monoclonal↗
PubMed1997

Conservative surgery and radiotherapy for early-stage breast cancer using a lung density correction: the University of Michigan experience.

PURPOSE: Although an abundance of reports detail the successful use of definitive radiotherapy of the breast in the treatment in Stage I or II breast cancer, little data have been published concerning the use of lung density correction and its effect upon long-term outcome. As it has been the practice at the University of Michigan to routinely use lung density correction in the dose calculations to the breast, we retrospectively analyzed our results for local control, relapse-free, and overall survival. METHODS AND MATERIALS: Clinical records were reviewed of 429 women with Stage I or II breast cancer treated with lumpectomy, axillary dissection, and breast irradiation with or without systemic chemo/hormonal therapy. Tangential radiotherapy fields delivering 45 to 50 Gy were used to treat the entire breast. A boost was delivered in 95% of cases for a total tumor bed dose of 60 to 66 Gy. All treatment plans were calculated using a lung density correction. RESULTS: With a median follow up of 4.4 years, the 5-year actuarial rate of local control with local failure as the only site of first failure was 96% (95% CI 94-98%). Univariate analysis for local failure as only first failure found the following factors to statistically predict for increased risk of breast recurrence: young age (< or =35 years old), premenopausal status, tumor size >2 cm, positive family history, and positive microscopic margins. Multivariate analysis revealed young age and margin status to be the only factors remaining significant for local failure. The 5-year actuarial relapse-free survival was 85% (95% CI 81-89%); overall survival at 5 years was 90% (95% CI 87-94%). CONCLUSIONS: Lung density correction results in rates of local control, disease-free, and overall survival at 5 years that compare favorably with series using noncorrected unit density calculations. While we will continue to update our results with increasing follow-up, our 5-year data indicate that the use of lung-density correction for dosimetric accuracy does not compromise local control.

Adult↗
PubMed1997

The conservative management of Paget's disease of the breast with radiotherapy.

BACKGROUND: The purpose of this study was to evaluate the feasibility of breast-conserving therapy involving limited surgery and definitive radiotherapy as a treatment for Paget's disease, and to determine the disease free and overall survival associated with this approach. METHODS: The authors retrospectively reviewed the charts of all patients treated during the period 1980-1994 for Paget's disease of the breast who did not present with a palpable mass or mammographic density. Through a collaborative review, 30 cases were identified. A biopsy confirming the presence of typical Paget's cells was performed on all patients. All patients received external beam radiotherapy to the breast, with a median dose of 50 gray (Gy). Ninety-seven percent received a boost to the remaining nipple or tumor bed, with a median dose to the tumor bed of 61.5 Gy. RESULTS: The median follow-up for surviving patients was 62 months. Three patients (10%) developed a recurrence in the breast as the only site of first failure, and 2 additional patients (7%) experienced failure in the breast as a component of first failure. The median time to local failure was 69 months. The 5- and 8-year actuarial estimates of local failure as the only site of first failure were 9% (95% confidence interval [CI], 0-20%) and 16% (95% CI, 0-31%), respectively. Of the 5 patients with local failures, 3 were among 22 patients (14%) who underwent complete resection of the nipple or nipple-areola complex, compared with 2 failures among 6 patients (33%) after partial resection (P = 0.29). There were no failures among 2 patients who had a biopsy only. Four of 5 local failures were salvaged by mastectomy, and 3 of these patients were free of disease after a median follow-up of 52 months. The 5- and 8-year estimates of disease free survival for the overall series were both 95% (95% CI, 87-100%); cause specific overall survival was 100% at 8 years. CONCLUSIONS: Breast-conserving therapy involving complete resection of the nipple-areola complex followed by definitive radiotherapy is a viable alternative to mastectomy in the treatment of Paget's disease. High rates of disease free and cause specific survival, in addition to adequate local control, justify consideration of a conservative approach.

Adult↗
PubMed1997

Dose-volume complication analysis for visual pathway structures of patients with advanced paranasal sinus tumors.

PURPOSE: The purpose of the present work was to relate dose and volume information to complication data for visual pathway structures in patients with advanced paranasal sinus tumors. METHODS AND MATERIALS: Three-dimensional (3D) dose distributions for chiasm, optic nerve, and retina were calculated and analyzed for 20 patients with advanced paranasal sinus malignant tumors. 3D treatment planning with beam's eye view capability was used to design beam and block arrangements, striving to spare the contralateral orbit (to lessen the chance of unilateral blindness) and frequently the ipsilateral orbit (to help prevent bilateral blindness). Point doses, dose-volume histogram analysis, and normal tissue complication probability (NTCP) calculations were performed. Published tolerance doses that indicate significant risk of complications were used as guidelines for analysis of the 3D dose distributions. RESULTS: Point doses, percent volume exceeding a specified published tolerance dose, and NTCP calculations are given in detail for patients with complications versus patients without complications. Two optic nerves receiving maximum doses below the published tolerance dose sustained damage (mild vision loss). Three patients (of 13) without optic nerve sparing and/or chiasm sparing had moderate or severe vision loss. Complication data, including individual patient analysis to estimate overall risk for loss of vision, are given. CONCLUSION: 3D treatment planning techniques were used successfully to provide bilateral sparing of the globe for most patients. It was more difficult to spare the optic nerves, especially on the ipsilateral side, when prescription dose exceeded the normal tissue tolerance doses. NTCP calculations may be useful in assessing complication risk better than point dose tolerance criteria for the chiasm, optic nerve, and retina. It is important to assess the overall risk of blindness for the patient in addition to the risk for individual visual pathway structures.

Blindness↗
PubMed1997

Results of 3D conformal radiotherapy in the treatment of localized prostate cancer.

PURPOSE: 3D conformal radiotherapy (3D CRT) has been shown to decrease acute morbidity in the treatment of prostate cancer. Therapeutic outcome and late morbidity data have been accumulating. To evaluate the results of 3D CRT for the treatment of prostate cancer, we analyzed the outcome of a large series of patients treated with conformal techniques. MATERIAL AND METHODS: From January 1987 through June 1994, 707 patients with localized prostate cancer were treated with 3D CRT. Patients with pathologically-confirmed pelvic lymph node metastasis, treated with pre-irradiation (preRT) androgen ablation, or treated post-prostatectomy were excluded. All had CT obtained specifically for treatment planning, multiple structures contoured on the axial images, and beam's-eye view conformal beams edited to provide 3D dose coverage. Median follow-up is 36 mos; 70 patients have been followed longer than 5.5 years. Six hundred three had T1-T2 tumors. PreRT prostate specific antigen (PSA) was available for 649 patients: median preRT PSA was 12.9 ng/ml, 209 patients had preRT PSA > 20 ng/ml. The median dose of radiation was 69 Gy; 102 patients received > or = 69 Gy. Biochemical failure was defined as: 1) two consecutive PSA rises over 2.0 ng/ml if nadir PSA < or = 2.0 ng/ml, 2) two consecutive PSA rises over nadir if nadir PSA > 2.0 ng/ml, or 3) initiation of hormonal therapy after RT. Complications were graded using the RTOG system. RESULTS: PreRT PSA and Gleason score emerged as independent indicators of biochemical control (bNED). Patients with preRT PSA > 10 had a significantly worse bNED at 5 years than patients with preRT PSA < or = 10. Five-year bNED was determined according to preRT PSA: PSA < or = 4, 88%; PSA > 4 < or = 10, 72%; PSA > 10 < or = 20, 43%; and PSA > 20, 30%. Patients with Gleason score > or = 7 also had a significantly worse bNED than patients with Gleason score < 7. Patients were divided into two prognostic groups: a favorable group with PSA < or = 10, Gleason score < 7, and T1-T2 tumors, and an unfavorable group with PSA > 10, Gleason score > or = 7 or T3-T4 tumors and studied for the effect of dose on bNED status. The bNED at 5 years was 75% for the favorable group and 37% for the unfavorable group. In addition, a group that might be considered a surgical subset was reviewed: patients with PSA < or = 10, Gleason score < or = 7, and T1-T2 tumors who were < 70 years old. This subset had an 84% 5-year bNED rate and 98% 5-year overall survival. Complications with the techniques used here are very low: 3% risk at 7 years of Grade 3-4 complications and 1% risk at 7 years of Grade 3 bladder complications (no Grade 4). CONCLUSION: 3D CRT allows for treatment of prostate cancers with a very low risk of complications. Patients with relatively early disease as defined by preRT PSA, Gleason score < 7, and T1-2 tumors and patients who are candidates for radical prostatectomy have excellent 5-year bNED rates. Patients with adverse prognostic factors have a high risk of biochemical recurrence and are candidates for innovative therapy.

Adult↗
PubMed1997

Dose escalation for non-small cell lung cancer using conformal radiation therapy.

PURPOSE: Improved local control of non-small cell lung cancer (NSCLC) may be possible with an increased dose of radiation. Three-dimensional radiation treatment planning (3D RTP) was used to design a radiation therapy (RT) dose escalation trial, where the dose was determined by (a) the effective volume of normal lung irradiated, and (b) the estimated risk of a complication. Preliminary results of this trial were reviewed. METHODS AND MATERIALS: A graph of the iso-normal tissue complication probability (NTCP) levels associated with a dose and effective volume (V(eff)) was derived, using normal tissue parameters derived from the literature. This led to a dose escalation schema, where patients were sorted into 1 of 5 treatment bins, determined by the V(eff) of the best possible treatment plan. The starting doses ranged from 63 to 84 Gy. Each treatment bin was then escalated separately, as in Phase I dose escalation fashion, with Grade > or = 3 radiation pneumonitis defined as dose limiting. To allow for dose escalation, we required patient follow-up to be > or = 6 months for at least three patients. 3D treatment planning was used to irradiate only the radiographically abnormal areas, with 2.1 Gy (corrected for lung inhomogeneity)/day. Clinically uninvolved lymph nodes were not treated prophylactically. RESULTS: A total of 48 NSCLC patients have been treated (Stage I/II: 18 patients; Stage III: 28 patients; mediastinal recurrence postsurgery: 2 patients). No radiation pneumonitis has been observed in the 30 patients currently evaluable beyond the 6-month time point. All treatment bins have been escalated at least once. Current doses in the five treatment bins are 69.3, 69.3, 75.6, 84, and 92.4 Gy. None of the 15 evaluable patients in any bin with > or = 30% NTCP experienced clinical radiation pneumonitis, implying that the actual risk is < 20% (beta error rate 5%). Despite the observation of the clinically negative lymph nodes at high risk, there has been no failure in the untreated mediastinum as the sole site of first failure. Three of 10 patients receiving > or = 84 Gy have had biopsy proven residual or locally recurrent disease. CONCLUSION: Successful dose escalation in a volume-dependent organ can be performed using this technique. By incorporating the effective volume of irradiated tissue, some patients have been treated to a total dose of radiation over 50% higher than traditional doses. The literature-derived parameters appear to overestimate pneumonitis risk with higher volumes. There has been no obvious negative effect due to exclusion of elective lymph node radiation. When completed, this trial will have determined the maximum tolerable dose of RT as a single agent for NSCLC and the appropriate dose for Phase II investigation.

Adenocarcinoma↗
PubMed1997

What a surgeon needs to know about radiation.

BACKGROUND: A better understanding of the physical and biologic principles of radiation oncology, along with improvements in the technical and clinical aspects of this field, have been gained in recent years. Some of these aspects are presented, with an emphasis on their relevance to the oncologic surgeon. RESULTS: Recent innovations have improved our ability to deliver high radiation doses safely and to increase the therapeutic ratio of radiation. They include the concurrent administration of radiation sensitizers and chemotherapy, altered fractionation schemes, and the conformal delivery of radiation using sophisticated imaging and planning tools. CONCLUSIONS: The increasing efficacy of radiation, resulting from innovations described in this review and others, enhances the role of radiotherapy in the struggle against cancer.

Antineoplastic Agents↗
PubMed1997

Volume and dose parameters for survival of non-small cell lung cancer patients.

BACKGROUND AND PURPOSE: To determine the effect of tumor volume and dose factors derived from 3-D treatment planning dose distributions on survival outcome for non-small cell lung cancer patients. MATERIALS AND METHODS: Seventy-six consecutive patients diagnosed with medically inoperable or locally advanced, unresectable non-small cell lung cancer planned with 3-D treatment planning between 1986 and 1992 were the subject of this retrospective study. Patient characteristics and dosimetric parameters were analyzed for influence on overall survival and local progression-free survival (LPFS) using univariate and multivariate analysis. RESULTS: Nodal stage and stage were the most significant factors for overall survival and LPFS duration on both univariate and multivariate analysis. We found a wide range of primary tumor volume sizes for each stage. Patients with tumor volumes <200 cm3 had longer survival (P = 0.047). In an analysis stratifying patients into four groups by tumor volume (<200 cm3 versus >200 cm3) and nodes (negative versus positive), patients in the group with no nodal disease and <200 cm3 tumor volumes survived longer than patients in any other group (P = 0.046). No dose factors were statistically significant for longer survival. Longer LPFS was seen for (a) isocenter dose >70 Gy (P = 0.055) for the overall group of patients, (b) within a subgroup with no nodal disease and >73 Gy (P = 0.054), and (c) within a subgroup with no nodal disease and tumor volume <200 cm3 receiving >73 Gy (P = 0.086). CONCLUSIONS: Several findings from the volume and dosimetric analysis in this study are noteworthy. Stage was found to be a poor predictor of primary tumor volume size. Also, tumor volume size (<200 cm3) in conjunction with nodal status (negative nodes) had an impact on survival though there was a mix of stage (I, IIIa, IIIb) in this group of patients. Finally, dose appears to influence local control (LPFS) for the overall group of patients and when tumor volumes are <200 cm3. Our data indicate that outcome following radiation may be better predicted by a staging system that takes into account tumor volume and nodal spread rather than a system that is largely based on anatomic location of disease. Dose prescription for lung cancer treatment might better be written based on tumor volume size.

Carcinoma, Non-Small-Cell Lung↗
PubMed1996

Parotid gland sparing in patients undergoing bilateral head and neck irradiation: techniques and early results.

PURPOSE: To minimize xerostomia in patients receiving bilateral head and neck irradiation (RT) by using conformal RT planning to spare a significant volume of one parotid gland from radiation. METHODS AND MATERIALS: The study involved 15 patients with head and neck tumors in whom bilateral neck radiation was indicated. The major salivary glands and the targets (tumor, surgical bed, metastases to lymph nodes, and the locations of lymph nodes at risk for metastases) were outlined on axial computed tomography images. Beam's-eye view (BEV) displays were used to construct conformal beams that delivered the prescribed doses to the targets while sparing from direct radiation most of one parotid gland. The gland that was planned to be spared resided in the neck side that was judged in each patient to be at a lesser risk of metastatic disease. Major salivary gland flow rates and the responses to a subjective xerostomia questionnaire were assessed before, during, and after radiation. RESULTS: Radiation planning for patients with central oropharyngeal tumors required the generation of multiple axial nonopposed beams. The resulting isodoses encompassed the targets, including the retropharyngeal nodes and the jugular nodes up to the base of skull bilaterally, while limiting the dose to the oral cavity, spinal cord, and one parotid gland. For patients with lateralized tumors, the ipsilateral neck side was treated up to the base of the skull; in the contralateral neck side, the treatment included the subdigastric nodes but excluded the jugular nodes at the base of the skull and most of the parotid gland. This was accomplished by a moderate gantry angle that was chosen using the BEV displays. Three months following the completion of radiation, the spared parotid glands retained on average 50% of their unstimulated and stimulated flows. In contrast, no saliva flow was measured from the unspared glands in any of the patients. Subjective xerostomia was absent, mild, or not different from that reported before radiation in 10 of 15 patients (67%). CONCLUSION: Partial parotid gland sparing is feasible by using three-dimensional planning in patients undergoing bilateral head and neck radiation. Approximately 50% of the saliva flow from the spared glands may be retained, and most patients thus treated have no or mild xerostomia in the early period after the completion of radiation. Whether tumor control and late complications are comparable to standard radiation will be assessed as more experience is gained.

Aged↗
PubMed1996

Analysis of localization errors in the definition of the mantle field using a beam's eye view treatment-planning system.

PURPOSE: Reports of the treatment of Hodgkin's disease (HD) with radiotherapy using the mantle field technique have demonstrated that coverage of disease by the field blocks significantly compromises outcome. It is our hypothesis that the availability of computerized tomography images reduces the incidence of localization error, and that the use of beam's eye view treatment planning techniques may further improve localization. The purpose of this report is to assess the possible contribution of a three-dimensional treatment-planning system to tumor localization and mantle block drawing in patients with HD. MATERIALS AND METHODS: We evaluated the localization error rate of four experienced radiation oncologists as they drew the lung blocks for the mantle field. The analysis included 16 patients treated with mantle fields in our department between 1989 and 1991. In each case our computerized three-dimensional treatment planning system was used to generate a beam's eye view display of tumor volumes. Simulation radiographs for all 16 patients were overlaid with acetate film, and lung blocks were drawn by clinicians using only the simulation radiographs for reference. The process was repeated with the thoracic CT scans available for reference. The mantle block contours for each trial were then superimposed upon the beam's eye view plots of tumor volumes. The beam's eye view plot was our benchmark for the evaluation of errors of tumor localization. Localization errors were defined as touching or overlap of the shielding blocks onto tumors. RESULTS: There was a high degree (p < 0.0003) of consistency in scoring across all pairing of clinicians and the results from all four were polled for the analysis. The overall error rate using the simulation radiographs alone was 18%. The rate was significantly lower (13%) when the CT images were available (p = 0.038). The axillary region had the highest localization error rate (41.7% with CT available and 27.1% with CT available) and the superior mediastinum had the lowest error rate (10.7% without CT, 8.5% with CT). Compared with a system such as beam's eye view, which could reduce the localization error rate to zero, the error rate with CT scans available is still significant [95% confidence interval (CI = 10-17.1%)]. Localization errors were more likely with increasing tumor size when CT scans were not available (p = 0.029). A similar trend was not seen when CT scans were available (p = 0.2). In a multivariate analysis, the use of CT scans predicted for reduced localization error rate (p = 0.03). Tumors in the axilla and inferior mediastinum had a greater relative risk than those in the superior mediastinum (p = 0.0001) CONCLUSION: The availability of CT imaging offers an advantage in the outlining of the mantle field in the treatment of Hodgkin's disease. When the error rate is evaluated using a beam's eye view treatment planning system, a significant proportion of tumors may be overlapped by the outlined mantle blocks even when CT images are available for reference. The use of beam's eye view treatment planning in mantle field definition, especially for tumors in the axillary region, may reduce the incidence of geographic misses.

Adult↗
PubMed1996

Influence of patient characteristics, socioeconomic factors, geography, and systemic risk on the use of breast-sparing treatment in women enrolled in adjuvant breast cancer studies: an analysis of two intergroup trials.

PURPOSE: To investigate the frequency of breast-sparing treatment among breast cancer patients subsequently enrolled in national cooperative group studies of adjuvant chemotherapy. PATIENTS AND METHODS: A data base was formed of 5,172 patients randomized onto two intergroup trials. Lumpectomy rates were analyzed within study-defined risk strata and across geographic regions. Significant predictors of lower lumpectomy usage were determined in multivariate analyses with variables that described patient and disease characteristics, systemic risk strata, geographic region, and socioeconomic indicators based on zip code of residence. RESULTS: Breast-conservation rates were 30% in the node-negative and 15% in the node-positive trials, with a wide geographic variation within each study (range, 14% to 49% and 9% to 31%, respectively). Lumpectomy use declined with increasing tumor size and did not exceed 40% even for tumors < or = 1 cm with negative nodes. With increasing risk of systemic relapse, frequency of lumpectomy declined (rates for five strata in order of increasing systemic risk: 41%, 33%, 24%, 18%, and 11%), even though these strata were not known at the time of the surgical decision. A logistic model confirmed the joint significance of geographic region and systemic risk. An exploratory model that adjusted for all important variables identified the following significant predictors of lower lumpectomy use: positive nodes; many positive nodes, increased systemic risk; tumor size > or = 2.0 cm; older age; South, Central or non-New England regions; and either lack of college degree or lower income levels. CONCLUSION: Breast-sparing therapy was used in the minority of women subsequently accrued to two national adjuvant breast cancer studies, even though this cohort and their referring surgeons represented a select population. Although multiple concrete factors were independent predictors of lower lumpectomy rates, prospective research is needed into how patients and their physicians approach the mastectomy versus lumpectomy decision.

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