Biomedical subjects

L W Davis

Publications and source records attributed to L W Davis.

At least 37 records · Page 2Linked to original sources

PubMed1991

Randomized study of preoperative versus postoperative radiation therapy in advanced head and neck carcinoma: long-term follow-up of RTOG study 73-03.

This is a report of a 10-year median follow-up of a randomized, prospective study investigating the optimal sequencing of radiation therapy (RT) in relation to surgery for operable advanced head and neck cancer. In May 1973, the Radiation Therapy Oncology Group (RTOG) began a Phase III study of preoperative radiation therapy (50.0 Gy) versus postoperative radiation therapy (60.0 Gy) for supraglottic larynx and hypopharynx primaries. Of 277 evaluable patients, duration of follow-up is 9-15 years, with 7.6% patients lost to follow-up before 7 years. Loco-regional control was significantly better for 141 postoperative radiation therapy patients than for 136 preoperative radiation therapy patients (p = 0.04), but absolute survival was not affected (p = 0.15). When the analysis was restricted to supraglottic larynx primaries (60 postoperative radiation therapy patients versus 58 preoperative radiation therapy patients), the difference for loco-regional control was highly significant (p = .007), but not for survival (p = 0.18). In considering only supraglottic larynx, 78% of loco-regional failures occurred in the first 2 years. Thirty-one percent (18/58) of preoperative patients failed locally within 2 years versus 18% (11/60) of postoperative patients. After 2 years, distant metastases and second primaries became the predominant failure pattern, especially in postoperative radiation therapy patients. This shift in the late failure pattern along with the increased number of unrelated deaths negated any advantage in absolute survival for postoperative radiation therapy patients. The rates of severe surgical and radiation therapy complications were similar between the two arms. Because of an increased incidence of late distant metastases and secondary primaries, additional therapeutic intervention is required beyond surgery and postoperative irradiation to impact significantly upon survival.

Adult↗

PubMed1991

The effect of local-regional control on distant metastatic dissemination in carcinoma of the head and neck: results of an analysis from the RTOG head and neck database.

A retrospective analysis of the effect of local control on the development of distant metastases was performed in 2648 patients with carcinoma of the head and neck selected from the RTOG database. The 5-year time-adjusted incidence of distant metastases was 21% for patients who were in local-regional control at 6 months after the start of treatment, compared to 38% for local-regional failure patients (p less than 0.001). The incidence of distant metastases detected between the interval of 6 months to 2.5 years after treatment was significantly increased in patients with tumors of the oral cavity, oropharynx, supraglottic larynx, and glottis who developed local-regional failure within this time period, compared to those who remained locally controlled (19% distant metastases for local-regional failure vs 7% for local-regional control (p less than 0.001)). In contrast, there as no difference in the incidence of distant metastases in patients with carcinoma of the nasopharynx or hypopharynx regardless of the local-regional disease status. A Cox proportional hazards regression analysis demonstrated that local-regional control was the most significant variable affecting the development of distant metastases, followed by tumor site, N-stage, and T-stage. For all tumor sites, except for the hypopharynx and nasopharynx, improvements in local-regional control are likely to improve survival. Tumors of the hypopharynx and nasopharynx have a higher probability of micro-metastatic dissemination at the time of initial diagnosis, and until effective methods to treat disseminated disease are developed, the effect of local control on survival will not be readily discerned.

Carcinoma, Squamous Cell↗

PubMed1990

High energy (42-66 MeV reactions) fast neutron dose optimization studies in the head and neck, thorax, upper abdomen, pelvis and extremities.

Five hundred and fifty patients were entered into a set of dose-searching studies designed to determine normal tissue tolerance to high energy (42-66 MeV reactions) fast neutrons delivered in 12 equal fractions over 4 weeks. Participating institutions included: The Fermilab (66 MeV p+----Be), The University of Washington (50 MeVp+----Be), U.C.L.A. (45 MeVH-----Be), M.D. Anderson Hospital (42 MeVH-----Be), and The Cleveland Clinic (42 MeVp+----Be). Patients were stratified by treatment facility and then randomized to receive 16, 18 or 20 Gy for tumors located in the upper abdomen or pelvis, and 18, 20 or 22 Gy for tumors located in the head and neck, thorax or extremities. Following completion of the randomized protocols, additional patients were studied at the 20.4 Gy level in the head and neck, thorax and pelvis. Normal tissue effect scoring was accomplished using the RTOG-EORTC acute and late normal tissue effect scales. Acute Grade 3 + toxicity rates in the head and neck were 19% for 20/20.4 Gy and 20% for 22 Gy. Time adjusted late toxicity rates in the head and neck at 12 months were 15% for 20/20.4 Gy and 0% for 22 Gy. The 18 Gy treatment arm of the head and neck protocol was dropped early in the study after only two patients were accrued. For cases treated in the thorax, acute Grade 3 + toxicity rates were 6% for 18 Gy, 15% for 20/20.4 Gy and 7% for 22 Gy. Late toxicity rates at 12 months were 0% for 18 Gy, 11% for 20/20.4 Gy and 18% for 22 Gy. Acute Grade 3+ toxicity rates in the upper abdomen were 0% for 16 Gy, 8% for 18 Gy and 12% for 20 Gy. There were no Grade 3 + late toxicities in the upper abdomen. In the pelvis, acute Grade 3 + toxicity rates were 0% for 16 Gy, 3% for 18 Gy and 3% for 20/20.4 Gy. Late Grade 3 + toxicities at 24 months were 20% for 16 Gy, 5% for 18 Gy and 24% for 20/20.4 Gy. In extremities, acute Grade 3 + toxicity rates were 7% for 20 Gy and 21% for 22 Gy while at 12 months, late Grade 3 + toxicity rates were 14 and 35%, respectively. The 18 Gy treatment arm of the extremities protocol was dropped early in the study after only two patients were accrued. Factors associated with normal tissue effects in addition to treatment dose are discussed.

Abdominal Neoplasms↗

PubMed1990

Transient and chronic neurological complications of fast neutron radiation for adenocarcinoma of the prostate.

The records of 132 patients participating in clinical trials using fast neutron (n = 94), mixed neutron and photon (n = 16), or conventional photon (n = 22) irradiation for primary management of prostatic cancer were retrospectively reviewed to assess treatment-related neurological complications. With a median follow-up of 14 months (range 1 to 101 months), 31/132 patients (26 neutron, 3 mixed beam, 2 photon) have experienced either sciatica beginning during or shortly after treatment, or diminished bladder or bowel continence that developed at a median time of 6.5 months following treatment. Sciatica responded to oral steroids and was usually self-limited, whereas sphincter dysfunction appears to be permanent. Pre-treatment risk factors for complications included a history of hypertension, diabetes, cigarette smoking or peripheral vascular disease, with 81% of affected patients having one or more risk factors compared with 55% of unaffected patients (p = 0.01). Seven patients have moderate (5) or severe (2) residual problems, all in the cohorts receiving neutrons (6/7) or mixed beam therapy (1/7).

Adenocarcinoma↗

PubMed1990

A technique for treating local breast cancer using a single set-up point and asymmetric collimation.

Using both pairs of asymmetric jaws of a linear accelerator local-regional breast cancer may be treated from a single set-up point. This point is placed at the abutment of the supraclavicular fields with the medial and lateral tangential fields. Positioning the jaws to create a half-beam superiorly permits treatment of the supraclavicular field. Positioning both jaws asymmetrically at midline to define a single beam in the inferoanterior quadrant permits treatment of the breast from medial and lateral tangents. The highest possible matching accuracy between the supraclavicular and tangential fields is inherently provided by this technique. For treatment of all fields at 100 cm source to axis distance (SAD) the lateral placement and depth of the set-up point may be determined by simulation and simple trigonometry. We elaborate on the clinical procedure. For the technologists treatment of all fields from a single set-up point is simple and efficient. Since the tissue at the superior border of the tangential fields is generally firmer than in mid-breast, greater accuracy in day-to-day set-up is permitted. This technique eliminates the need for table angles even when tangential fields only are planned. Because of half-beam collimation the limit to the tangential field length is 20 cm. Means will be suggested to overcome this limitation in the few cases where it occurs. Another modification is suggested for linear accelerators with only one independent pair of jaws.

Breast Neoplasms↗

PubMed1989

Impact of initial quality control review on study outcome in lung and head/neck cancer studies--review of the Radiation Therapy Oncology Group experience.

The Radiation Therapy Oncology Group (RTOG) initiated cooperative clinical trials in 1971. In 1978, RTOG developed a formalized program of Quality Control (QC) divided into initial and final phases. The initial review process consisted of two steps. The first phase of review is an evaluation performed by a radiation oncologist to verify treatment plan and field borders. The second portion of the initial review process originally consisted of dosimetry calculation verification based on machine data provided by the regional Radiological Physics Center and treatment planning data provided by the accessioning institution. Between 1978 and December 31, 1987, a total of 11,343 cases in 96 RTOG protocols, excluding particle studies, underwent initial review. Of this number, 2227 patients were entered in lung cancer studies and 1341 patients were entered in head/neck cancer studies. Initial review was carried out in 2089 (93.8%) of the lung cancer cases. Missing or delayed data accounted for 138 (6.2%) cases not reviewed initially. In head/neck cancer trials, 1251 (93.2%) received initial review and 90 (6.8%) did not. Our findings suggest that there are sharply defined but long lasting learning experiences involved in clinical trial participation. Consideration may be given to modifying the initial review process to use random sampling of cases accessioned by experienced investigators in ongoing clinical trials and to continuing the total case evaluation on all new studies and cases entered by inexperienced investigators or investigators/institutions with unsatisfactory performance. Recommendations regarding initial review of other sites will await evaluation of the impact of initial review on those sites.

Head and Neck Neoplasms↗

PubMed1989

Second malignancies in patients who have head and neck cancer: incidence, effect on survival and implications based on the RTOG experience.

The development of second malignant tumors (SMTs), in patients who have had their first tumor treated successfully, represents a serious limitation of current therapeutic strategies for head and neck cancers. To improve our understanding of the current magnitude of the problem and the various factors that might influence its importance, we reviewed the Radiation Therapy Oncology Group's (RTOG) prospectively collected registry of all head and neck patients seen in participating member institutions between February 1977 and April 1980. A total of 928 patients were identified who had squamous cell carcinomas of the head and neck region, no prior or coincident history of another malignant tumor, and whose planned treatment consisted of radiation therapy only. A total of 110 second, independent, malignant tumors occurred in these patients. Overall, the estimated risk of developing a second tumor within 3 years of radiotherapy was 10%, within 5 years 15%, and within 8 years 23%. Minor differences in frequency were observed for different primary sites. These SMTs unquestionably influenced subsequent survival adversely. Analysis of the database also revealed that the extent of the primary tumor influenced the risk of a second; most occurred in patients who presented with the smallest primary tumors because of their better survival. Our data indicate that preventive medicine should have its greatest impact in those patients who are treated for an early stage primary tumor.

Carcinoma, Bronchogenic↗

PubMed1989

Mixed neutron/photon irradiation of unresectable squamous cell carcinomas of the head and neck: the final report of a randomized cooperative trial.

Three hundred and twenty-seven patients with inoperable squamous cell carcinomas of the head and neck were entered on a randomized study comparing a mixture of neutron and photon ("mixed beam") radiation therapy with photon/electron radiation therapy. Neutron treatment was delivered with fixed-beam, physics-laboratory-based equipment. Patients with histologically proven tumors of T-stage T2, T3, or T4 and any N-stage were eligible for randomization. Primary tumor sites were limited to cancers originating in the oral cavity, oropharynx, supraglottic larynx, or hypopharynx. Patients entered on this study now have a minimum at-risk follow-up period of 6 years. Study results reveal no significant differences in overall loco-regional tumor control rates or survival. Subgroup analysis reveals significant differences based on whether or not patients presented with positive lymph nodes. Loco-regional tumor control rates for patients presenting with positive lymph nodes were 30% for mixed-beam-treated patients versus 18% for photon-treated patients (p = 0.05). Loco-regional tumor control rates for patients presenting without positive lymph nodes were 64% for photon-treated patients and 33% for mixed-beam-treated patients (p = 0.004). Control of tumor located in the nodal sites favored mixed beam over photons by a margin of 45% (49/109) to 26% (23/87) with a significance of p = 0.004. Possible explanations for these contradictory findings are discussed.

Adult↗

PubMed1989

The role of hemoglobin concentration in the outcome of misonidazole-sensitized radiotherapy of head and neck cancers: based on RTOG trial #79-15.

Recent data from the DAHANCA (Danish Head and Neck Cancer) 2 study implies a positive effect of high hemoglobin concentration in concert with misonidazole for the treatment of head and neck cancers by radiotherapy. We have therefore reviewed and updated our analysis of RTOG protocol 79-15, which included the effect of misonidazole plus radiotherapy in a presumably similar population. Despite additional follow-up and more sophisticated analysis, our analysis does not demonstrate an influence of hemoglobin concentration on any of the outcome measures we examined. Possible explanations for the difference in findings of RTOG 79-15 and DAHANCA 2 are discussed. Radiation therapy of head and neck squamous cancers, Hypoxia and hemoglobin conc. in head and neck cancers, Oral cavity cancer, Effect of radiation therapy, Oropharynx cancer, Hemoglobin and radiotherapy, Hemoglobin concentration, Effect upon radiotherapy, Irradiation of oropharynx cancer, Hgb effect.

Carcinoma, Squamous Cell↗

PubMed1989

Malignant glioma--a nemesis which requires clinical and basic investigation in radiation oncology.

Malignant gliomas account for 40% of all central nervous system malignancies. These are essentially localized neoplastic tumors that have defied most treatment. In spite of improved techniques, surgery is unlikely to increase survival further since true cancer operations cannot be performed. Radiation therapy has made a significant difference in outcome. Investigation in radiation oncology is essential for further improvement in the treatment of these tumors. The pattern of failure is local tumor recurrence, but the method to overcome this resistance to treatment is not clear. Radiation therapy techniques and inherent radio-resistance have been considered as possible reasons for failure. With newer imaging procedures, the extent of tumor can be more accurately defined allowing improved treatment planning. Identifying an effective treatment program is more difficult. Studies have documented the beneficial effect of radiation therapy, but the optimal dose or fractionation schedule has not been determined. Whereas some studies have reported improved survival using higher radiation doses, others have reported no benefit. More recently, studies of multiple daily fractionation schedules have been conducted using two or three daily fractions. Equally confusing results have been reported. Histologically, these tumors have necrotic areas and may be radioresistant due to hypoxic cells. Treatment methods designed to overcome the radioprotective effect of hypoxia have yielded disappointing results. The addition of hypoxic cell sensitizers has not produced the expected improvement in outcome. Studies using neutron radiation therapy report tumor control but not improved survival. Radiobiologic information is now available which may contribute to our understanding of the response of these tumors to radiation. Further laboratory and clinical investigation is required. Carefully designed clinical trials are needed to test new treatment concepts, and all radiation oncologists should be prepared to participate in such clinical studies.

Brain Neoplasms↗

PubMed1989

Chemotherapy following surgery for head and neck cancer. A Radiation Therapy Oncology Group Study.

The feasibility of chemotherapy of three courses of cis-platin and 120-h 5-fluorouracil (5-FU) infusion after definitive surgery, followed by standard radiotherapy, in patients with resectable locally advanced head and neck cancer was carried out in Radiation Therapy Oncology Group (RTOG). Seventy-nine percent of the patients had stage IV cancer, 65% of the tumors were moderately differentiated, and primary sites were 38% oropharynx and 28% larynx. Toxicity to chemotherapy was acceptable, with no life-threatening side effects. Nausea and vomiting were the most common side effects (78%) and were severe in 26%; 30% of patients experienced had leukopenia, 22% had anemia, 13% had thrombocytopenia, and 9% had renal impairment--all of which were mild and reversible. In six patients, chemotherapy was not given for medical conditions or because of patient refusal. Of 23 patients started on cis-platin and 5-FU postsurgery, 18 (78%) completed all three courses. Ninety-six percent of the patients finished adequate radiotherapy according to the protocol. With minimum follow-up of 24 months, 62% of the patients were alive. Of the expired patients, 5 died from other causes, without evidence of recurrence at the time of their death. It is our conclusion that chemotherapy with cis-platin and 5-FU infusion following definitive surgery is feasible on the group level, and a Phase III trial comparing this combined modality therapy to standard treatment of surgery and post-operative radiotherapy is underway by the Head and Neck Cancer Intergroup.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1989

Evaluation of neutron irradiation of pancreatic cancer. Results of a randomized Radiation Therapy Oncology Group clinical trial.

Between 1980-84, the Radiation Therapy Oncology Group conducted a trial in patients with untreated, unresectable localized carcinomas of the pancreas. Patients were randomly chosen to receive either 6,400 cGy with photons, the equivalent dose with a combination of photons and neutrons (mixed-beam irradiation), or neutrons alone. A total of 49 cases were evaluable, of which 23 were treated with photons, 11 with mixed-beam therapy, and 15 with neutrons alone. The median survival time was 5.6 months with neutrons, 7.8 months with mixed-beam radiation, and 8.3 months with photons. The median local control time was 6.7 months with neutrons, 6.5 months with mixed-beam radiation, and 2.6 months with photons. These differences are not statistically significant. Evidence of moderate-to-life-threatening gastrointestinal or hepatic injury was present in three patients treated with neutrons and one patient treated with photons. The causes of this apparent difference are discussed. This study demonstrates there is no evidence to suggest that neutron irradiation, either alone or in combination with photon irradiation, produces better local control or survival rates than photon irradiation.

Adenocarcinoma↗

PubMed1989

Neutron radiation therapy for unresectable non-small-cell carcinoma of the lung. A review.

Over 200 patients have been entered in five studies investigating the use of fast neutron radiation therapy in the treatment of non-small-cell carcinomas of the lung since 1983. The results of these studies have been inconsistent. Most studies did not show survival rates or local control advantages over standard photon radiation therapy. Side effects from studies employing mixed photon-neutron treatment plans or clinically oriented, high-energy cyclotrons were seen to be comparable to those of standard courses of radiation therapy, representing a considerable improvement over those studies utilizing low-energy cyclotrons for a full course of radiation therapy, which resulted in unacceptably high complication rates. A new phase III study utilizing high-energy isocentric neutron beams has been designed and implemented, and over 100 patients have been entered to date. The current status of fast neutron radiation therapy in the treatment of non-small-cell lung cancer is reviewed.

Carcinoma, Non-Small-Cell Lung↗

PubMed1989

Fast neutron radiotherapy for the treatment of carcinoma of the urinary bladder. A review of clinical trials.

The major clinical investigation employing fast neutrons in the treatment of invasive bladder cancer are reviewed. Although data suggest that preoperative radiation schedules employing neutrons may result in a greater degree of pathologic downstaging than conventional precystectomy photon regimens, this has not led to an improved survival rate for neutron-treated patients over photon-treated patients. Randomized clinical trials comparing primary neutron irradiation and primary photon irradiation do not disclose an advantage for neutrons over photons as measured by survival rate or freedom from local tumor recurrence. The late complications in normal pelvic tissues following neutron irradiation with low-energy beams exceed those experienced after photon irradiation and have led to an unexpectedly high rate of treatment-related morbidity and mortality. A partial explanation for the toxicity may be attributed to the use of neutron beams with poor depth dose characteristics for the treatment of what is a deep-seated malignancy. An additional explanation is the documented lack of a differential in radioresponsiveness to neutrons between the bladder primary tumor and adjacent normal pelvic tissues.

Carcinoma, Transitional Cell↗

PubMed1989

Fast neutron radiotherapy in the treatment of locally advanced adenocarcinoma of the prostate. Clinical experience and future directions.

The major clinical experiences using fast neutrons for the treatment of locally advanced prostatic carcinomas are reviewed. In all trials to date, there is evidence that treatment regimens employing a component of fast neutrons achieve results that equal or surpass those obtainable with conventional megavoltage external beam irradiation for comparable groups of patients. Late complications of neutron treatment have not exceeded the complication rate expected by photon irradiation. The structure of the current Radiation Therapy Oncology Group phase III randomized trial comparing neutron and photon treatment of patients with stages B2, C, and D1 disease is discussed.

Adenocarcinoma↗

PubMed1989

Neutron radiotherapy for malignant gliomas.

Neutron radiotherapy has been used for patients with malignant gliomas for over a decade; a substantial number of patients have been treated to date. Pathologic analysis of surgical specimens posttreatment and autopsy specimens have documented an increased antitumor effect of neutrons against malignant gliomas, compared with photon irradiation. However, results of neutron trials to date have not shown a survival advantage over conventional radiotherapy for these patients. This article reviews current surgical, radiotherapeutic, and chemotherapeutic approaches to these tumors, the rationale for neutron treatment, and the results of trials of neutron radiotherapy conducted to date for patients with malignant gliomas.

Brain Neoplasms↗

PubMed1989

Fast neutron radiotherapy for sarcomas of soft tissue, bone, and cartilage.

The basic radiobiological rationale for the use of fast neutron radiotherapy in the treatment of classically radioresistant tumors such as soft tissue sarcomas, osteogenic sarcomas, and chondrosarcomas is reviewed. There are no definitive randomized studies comparing high and low linear energy transfer radiotherapy for these tumor systems, but a review of published series is highly suggestive of a therapeutic advantage for fast neutrons. For soft tissue sarcomas, the local control rate is 53% (158 of 297) with fast neutrons, compared with 38% (49 of 128) with photons/electrons; for osteogenic sarcomas, the local control rate is 55% (40 of 73) with fast neutrons, compared with 21% (15 of 73) with photons/electrons; and for chondrosarcomas, the local control rate is 49% (25 of 51) with fast neutrons, compared with 33% (10 of 30) with photons/electrons. An ongoing clinical trial for these tumors is also described.

Bone Neoplasms↗

PubMed1988

Radiation Therapy Oncology Group (RTOG) studies in head and neck cancer.

Since its foundation in 1971, the RTOG has conducted a successful clinical research program in head and neck mucosal squamous cell carcinoma with 22 treatment protocols and one registry study which combined have accumulated data on over 5,500 patients. The RTOG was the first multicenter group to evaluate neoadjuvant chemotherapy before definitive radiation with its methotrexate study. Although the study was negative, RTOG has since conducted five pilot or phase II studies of neoinduction or concurrent chemotherapy with radiation therapy in patients with inoperable tumors. The last study showed that radiation concurrent with cisplatinum was tolerable with a suggestion of increased antitumor effect. In patients with potentially resectable tumors, RTOG has completed a pilot study of combination chemotherapy administered either before or after the surgery with radiotherapy. Based upon its findings, the treatment sequence, surgery-chemotherapy-radiotherapy, was chosen as the experimental arm for a new phase III study. This study was subsequently adopted by the head and neck intergroup mechanism as its study (INT 0034/RTOG 8503). RTOG has investigated the optimal timing of radiotherapy with surgery. The 7303 study established that postoperative radiotherapy achieved significantly better locoregional control but not improved absolute survival. Approximately 30% of the patients on each arm failed to complete both modalities. Even when comparison is restricted to patients who completed both modalities, postoperative radiotherapy still produced the better locoregional control. Efforts to overcome the limitations imposed by tumor hypoxia through use of carbogen (95% O2 and 5% CO2) breathing or the radiosensitizer misonidazole during radiotherapy have been unsuccessful. In a phase I study, RTOG showed that 15 to 18 sessions of sensitized radiation can be safely delivered with the new radiosensitizer SR 2508 in contrast to only six such sessions with misonidazole. This promising radiosensitizer is now being tested in a phase III trial. RTOG has also investigated variations in fraction size, fraction number, and total radiation dose. In the 7102 study, split-course irradiation achieved equivalent antitumor results as compared to continuous daily irradiation but with less social alteration and cost to the patient. In the hyperfraction pilot study 7703, twice a day irradiation with 120 cGys up to 6,000 cGys proved to be tolerable.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗