Biomedical subjects

Thomas Guerrero

Publications and source records attributed to Thomas Guerrero.

17 recordsLinked to original sources

PubMed2006

Semi-automated CT segmentation using optic flow and Fourier interpolation techniques.

In radiotherapy treatment planning, tumor volumes and anatomical structures are manually contoured for dose calculation, which takes time for clinicians. This study examines the use of semi-automated segmentation of CT images. A few high curvature points are manually drawn on a CT slice. Then Fourier interpolation is used to complete the contour. Consequently, optical flow, a deformable image registration method, is used to map the original contour to other slices. This technique has been applied successfully to contour anatomical structures and tumors. The maximum difference between the mapped contours and manually drawn contours was 6 pixels, which is similar in magnitude to difference one would see in manually drawn contours by different clinicians. The technique fails when the region to contour is topologically different between two slices. A solution is recommended to manually delineate contours on a sparse subset of slices and then map in both directions to fill the remaining slices.

Algorithms↗

PubMed2006

Comparison of outcomes for patients with medically inoperable Stage I non-small-cell lung cancer treated with two-dimensional vs. three-dimensional radiotherapy.

PURPOSE: This retrospective analysis was performed to assess the outcomes of three-dimensional (3D) conformal radiotherapy and two-dimensional (2D) planning. METHODS AND MATERIALS: Between 1978 and 2003, 200 patients with Stage I non-small-cell lung cancer (NSCLC) were treated with radiotherapy alone at M.D. Anderson Cancer Center. Eighty-five patients were treated with 3D conformal radiotherapy. For the 3D group, median age, radiation dose, and follow-up was 73 (range, 50-92), 66 Gy (range, 45-90.3 Gy), and 19 months (range, 3-77 months), respectively; and for the 2D group, 69 (range, 44-88), 64 Gy (range, 20-74 Gy), 20 months (range, 1-173 months), respectively. Overall survival (OS), disease-specific survival (DSS), disease-free survival (DFS), locoregional control (LRC), and distant metastasis-free survival (DMFS) rates were analyzed. RESULTS: There was no statistically significant difference in patient and tumor characteristics between 2D and 3D groups, except the 3D patients were older (p = 0.006). The OS, DSS, and LRC rates were significantly higher in patients who were treated by 3D conformal radiotherapy. Two- and 5-year OS for the 3D group were 68% and 36%, respectively, and 47% and 10% in the 2D group (p = 0.001). DSS at 2 and 5 years for the 3D group were 83% and 68%, respectively, vs. 62% and 29% in the 2D group (p < 0.001). LRC rates at 2 and 5 years for patients in the 3D group were 77% and 70% and 53% and 34% in the 2D group (p < 0.001). On univariate analysis elective, nodal irradiation was associated with decreased OS, DSS, and LRC. On multivariate analysis, 3D conformal radiotherapy was associated with increased OS and DSS. Male sex, age > or =70, weight loss > or =5%, and tumor size > or =4 cm were associated with decreased OS and DSS. CONCLUSIONS: This study demonstrates that 3D conformal radiotherapy improves outcomes in patients with medically inoperable Stage I NSCLC compared with 2D treatment and is an acceptable treatment for this group of patients.

Aged↗

PubMed2006

Novel method to calculate pulmonary compliance images in rodents from computed tomography acquired at constant pressures.

Our goal was to develop a method for generating high-resolution three-dimensional pulmonary compliance images in rodents from computed tomography (CT) images acquired at a series of constant pressures in ventilated animals. One rat and one mouse were used to demonstrate this technique. A pre-clinical GE flat panel CT scanner (maximum 31 line-pairs cm(-1) resolution) was utilized for image acquisition. The thorax of each animal was imaged with breath-holds at 2, 6, 10, 14 and 18 cm H2O pressure in triplicate. A deformable image registration algorithm was applied to each pair of CT images to map corresponding tissue elements. Pulmonary compliance was calculated on a voxel by voxel basis using adjacent pairs of CT images. Triplicate imaging was used to estimate the measurement error of this technique. The 3D pulmonary compliance images revealed regional heterogeneity of compliance. The maximum total lung compliance measured 0.080 (+/-0.007) ml air per cm H2O per ml of lung and 0.039 (+/-0.004) ml air per cm H2O per ml of lung for the rat and mouse, respectively. In this study, we have demonstrated a unique method of quantifying regional lung compliance from 4 to 16 cm H2O pressure with sub-millimetre spatial resolution in rodents.

Algorithms↗

PubMed2006

Dynamic ventilation imaging from four-dimensional computed tomography.

A novel method for dynamic ventilation imaging of the full respiratory cycle from four-dimensional computed tomography (4D CT) acquired without added contrast is presented. Three cases with 4D CT images obtained with respiratory gated acquisition for radiotherapy treatment planning were selected. Each of the 4D CT data sets was acquired during resting tidal breathing. A deformable image registration algorithm mapped each (voxel) corresponding tissue element across the 4D CT data set. From local average CT values, the change in fraction of air per voxel (i.e. local ventilation) was calculated. A 4D ventilation image set was calculated using pairs formed with the maximum expiration image volume, first the exhalation then the inhalation phases representing a complete breath cycle. A preliminary validation using manually determined lung volumes was performed. The calculated total ventilation was compared to the change in contoured lung volumes between the CT pairs (measured volume). A linear regression resulted in a slope of 1.01 and a correlation coefficient of 0.984 for the ventilation images. The spatial distribution of ventilation was found to be case specific and a 30% difference in mass-specific ventilation between the lower and upper lung halves was found. These images may be useful in radiotherapy planning.

Algorithms↗

PubMed2005

Quantification of regional ventilation from treatment planning CT.

PURPOSE: We describe a method of quantifying regional ventilation from the radiotherapy treatment planning computed tomography (CT) images, with the goal of developing functional images for treatment planning and optimization. METHODS AND MATERIALS: A series of exhalation breath-hold (eBH-CT) and inhalation breath-hold (iBH-CT) CT images obtained using a feedback-guided breath-hold technique for radiotherapy treatment planning was selected. The eBH-CT was mapped on a voxel-by-voxel basis to the iBH-CT using a deformable image registration algorithm. By using the average CT number over a 3 mm(3) region surrounding each pair of mapped voxels, the change in fraction of air per voxel (i.e., regional ventilation) was calculated. This methodology was applied to a series of 22 patients. The calculated total ventilation was compared to the change in contoured lung volumes between the exhalation and inhalation CTs (measured tidal volume). RESULTS: A significant correlation was found between the calculated and measured tidal volumes for the left (R = 0.982) and right (R = 0.985), and for both lungs combined (R = 0.985). In the resulting images, the regional ventilation was highly variable and corresponded with the spatial distribution of differences in the CT values (Hounsfield units) between the eBH-CT and the iBH-CT images. CONCLUSIONS: A method of quantifying regional ventilation from radiotherapy treatment planning CT data sets was demonstrated. The ventilation images can be used in plan optimization to minimize injury to functioning lung.

Algorithms↗

PubMed2005

A phase I clinical trial of thoracic radiotherapy and concurrent celecoxib for patients with unfavorable performance status inoperable/unresectable non-small cell lung cancer.

OBJECTIVES: Preclinical observations that selective cyclooxygenase-2 inhibitors enhance in vitro cell radiosensitivity and in vivo tumor radioresponse led to clinical trials testing therapeutic efficacy of these agents. Our study was designed to determine whether the COX-2 inhibitor celecoxib could be safely administered in doses within those approved by the Food and Drug Administration when used concurrently with thoracic radiotherapy in patients with poor prognosis non-small cell lung cancer (NSCLC). PATIENTS AND METHODS: The trial consisted of three cohorts of patients: (a) locally advanced NSCLC with obstructive pneumonia, hemoptysis, and/or minimal metastatic disease treated with 45 Gy in 15 fractions; (b) medically inoperable early-stage NSCLC treated with definitive radiation of 66 Gy in 33 fractions; and (c) patients who received induction chemotherapy but who were not eligible for concurrent chemoradiotherapy trials. These patients received 63 Gy in 35 fractions. Celecoxib was administered p.o. on a daily basis 5 days before and throughout the course of radiotherapy. Celecoxib doses were escalated from 200, 400, 600, to 800 mg/d given in two equally divided doses. Two to eight patients of each cohort were assigned to each dose level of celecoxib. RESULTS: Forty-seven patients were enrolled in this protocol (19 in cohort I, 22 in cohort II, and 6 in cohort III). The main toxicities were grades 1 and 2 nausea and esophagitis, and they were independent of the dose of celecoxib or radiotherapy schedule. Only two patients in group II developed grade 3 pneumonitis 1 month after treatment, one on 200 mg, and the other on 400 mg celecoxib. Celecoxib-related toxicity developed in 3 of 47 patients: an uncontrolled hypertension in one patient on 800 mg celecoxib and hemorrhagic episodes in 2 patients (shoulder hematoma in one and hemoptysis in the other) on 200 mg celecoxib who were on warfarin for other medical reasons. Of 37 patients evaluable for tumor response, 14 had complete response, 13 partial responses, and 10 stable or progressive disease. The actuarial local progression-free survival was 66.0% at 1 year and 42.2% at 2 years following initiation of radiotherapy. CONCLUSIONS: These results show that celecoxib can be safely administered concurrently with thoracic radiotherapy when given up to the highest Food and Drug Administration-approved dose of 800 mg/d, which we used. A maximal tolerated dose was not reached in this study. The treatment resulted in actuarial local progression-free survival of 66.0% at 1 year and 42.2% at 2 years, an encouraging outcome that warrants further assessment in a phase II/III trial.

Adult↗

PubMed2005

Dose-response relationship in locoregional control for patients with stage II-III esophageal cancer treated with concurrent chemotherapy and radiotherapy.

PURPOSE: To evaluate the correlation between radiation dose and locoregional control (LRC) for patients with Stage II-III unresectable esophageal cancer treated with concurrent chemotherapy and radiotherapy. METHODS AND MATERIALS: The medical records of 69 consecutive patients with clinical Stage II or III esophageal cancer treated with definitive chemoradiotherapy at the University of Texas M. D. Anderson Cancer Center between 1990 and 1998 were retrospectively reviewed. Of the 69 patients, 43 had received < or =51 Gy (lower dose group) and 26 >51 Gy (higher dose group). The median dose in the lower and higher dose groups was 30 Gy (range, 30-51 Gy) and 59.4 Gy (range, 54-64.8 Gy), respectively. Two fractionation schedules were used: rapid fractionation, delivering 30 Gy at 3 Gy/fraction within 2 weeks, and standard fractionation, delivering > or =45 Gy at 1.8-2 Gy/fraction daily. Total doses of <50 Gy were usually given with rapid fractionation. Cisplatin and 5-fluorouracil were administrated to 93% of the patients. RESULTS: The patient characteristic that differed between the two groups was that patients in the lower dose group were more likely to have had weight loss >5% (46.2% vs. 23.3%). The lower dose group had more N1 tumors, but the tumor classification and stage grouping were similar in the two groups. The median follow-up time for all patients was 22 months (range, 2-56 months). Patients in the higher dose group had a statistically significant better 3-year local control rate (36% vs. 19%, p = 0.011), disease-free survival rate (25% vs. 10%, p = 0.004), and overall survival rate (13% vs. 3%, p = 0.054). A trend toward a better distant-metastasis-free survival rate was noted in the higher dose group (72% vs. 59%, p = 0.12). The complete clinical response rate was significantly greater in the higher dose group (46% vs. 23%, p = 0.048). In both groups, the most common type of first failure was persistence of the primary tumor. Significantly fewer patients in the higher dose group had tumor persistence after treatment (p = 0.02). No statistically significant difference was found between the two groups in the pattern of locoregional or distant failure. The long-term side effects of chemoradiotherapy were similar in the two groups, although it was difficult to assess the side effects accurately in a retrospective fashion. On multivariate analysis, Stage II (vs. III) disease and radiation dose >51 Gy were independent predictors of improved LRC, and locoregional failure was an independent predictor of worse overall survival. CONCLUSION: Our data suggested a positive correlation between radiation dose and LRC in the population studied. A higher radiation dose was associated with increased LRC and survival in the dose range studied. The data also suggested that better LRC was associated with a lower rate of distant metastasis. A threshold of tumor response to radiation dose might be present, as suggested by the flattened slope in the high-dose area on the dose-response curve. A carefully designed dose-escalation study is required to confirm this assumption.

Adult↗

PubMed2005

A novel platform simulating irregular motion to enhance assessment of respiration-correlated radiation therapy procedures.

Respiratory motion continues to present challenges in the delivery of radiation therapy to tumors in the thorax and abdomen by causing movement of structures within those areas. Several approaches to account for this movement in the planning and delivery of treatment have been developed over the past several years. To assist in the development and assessment of various techniques for respiration-correlated radiation therapy, a platform capable of programmable irregular longitudinal motion has been designed and fabricated to simulate intrafractional respiratory motion. A sliding platform and the base on which it was mounted were constructed from polycarbonate plastic, and a stepper motor provided platform motion. Respiratory motion data, either artificially generated on a spreadsheet or extracted from respiratory monitoring files, were converted to a format appropriate for driving the stepper motor. Various phantoms were placed on top of the platform and used in studies related to respiration-correlated radiation therapy. Several applications of the platform were demonstrated, such as improving the quality of acquisition of time-dependent computed tomography image datasets, comparing various methods of acquiring such datasets, and implementing feedback-guided breath hold treatment delivery procedures. This study showed that a platform capable of programmable irregular motion is a useful tool for the development and assessment of procedures related to the effects of respiratory motion in radiation therapy.

Artifacts↗

PubMed2005

Elastic image mapping for 4-D dose estimation in thoracic radiotherapy.

PURPOSE: Demonstrate the path integration of a four-dimensional (4-D) dose distribution onto the 3-D anatomy. MATERIALS AND METHODS: A computer-generated 4-D thoracic phantom with a lung tumour was constructed. Eight respiratory phases were generated. A radiotherapy treatment plan was applied to all the phases resulting in a 4-D dose distribution. An elastic image registration algorithm was used to find the vector displacement between all the image elements and the end expiration phase. The path-integrated tissue dose distribution and each component dose distribution were compared with the planned dose distribution. RESULTS: Numerical path integration was performed to calculate the tissue dose distribution. Loss of tumour coverage was the predominant effect observed with tumour motion in this study. The loss was asymmetric and dependent on the tumour trajectory. CONCLUSION: The elastic image registration allowed an accurate path integration through a 4-D data set to produce an accurate 3-D tissue dose estimate.

Artifacts↗

PubMed2005

Semiautomated four-dimensional computed tomography segmentation using deformable models.

The purpose of this work is to demonstrate a proof of feasibility of the application of a commercial prototype deformable model algorithm to the problem of delineation of anatomic structures on four-dimensional (4D) computed tomography (CT) image data sets. We acquired a 4D CT image data set of a patient's thorax that consisted of three-dimensional (3D) image data sets from eight phases in the respiratory cycle. The contours of the right and left lungs, cord, heart, and esophagus were manually delineated on the end inspiration data set. An interactive deformable model algorithm, originally intended for deforming an atlas-based model surface to a 3D CT image data set, was applied in an automated fashion. Triangulations based on the contours generated on each phase were deformed to the CT data set on the succeeding phase to generate the contours on that phase. Deformation was propagated through the eight phases, and the contours obtained on the end inspiration data set were compared with the original manually delineated contours. Structures defined by high-density gradients, such as lungs, cord, and heart, were accurately reproduced, except in regions where other gradient boundaries may have confused the algorithm, such as near bronchi. The algorithm failed to accurately contour the esophagus, a soft-tissue structure completely surrounded by tissue of similar density, without manual interaction. This technique has the potential to facilitate contour delineation in 4D CT image data sets; and future evolution of the software is expected to improve the process.

Algorithms↗

PubMed2004

Induction chemotherapy improved outcomes of patients with resectable esophageal cancer who received chemoradiotherapy followed by surgery.

PURPOSE: To investigate the effect of induction chemotherapy (CHT) before trimodality therapy on the outcome of patients with resectable cancer of the esophagus. METHODS AND MATERIALS: This retrospective study included 81 consecutive patients with resectable cancer of the esophagus who received neoadjuvant chemoradiotherapy followed by esophagectomy between January 1990 and December 1998 (inclusive). Thirty-nine patients underwent chemoradiotherapy followed by esophagectomy (CHT/RT+S), 42 received additional induction CHT followed by CHT/RT+S (CHT+CHT/RT+S). Of the 81 patients, 47 were entered in institutional or national prospective trials (6 in the CHT/RT+S and 41 in the CHT+CHT/RT+S group). Induction CHT consisted of three courses of 5-fluorouracil (5-FU), cisplatin, and paclitaxel given in 28-day cycles in 37 patients (88.1%). Concurrent CHT was 5-FU and platinum based. The median radiation dose for patients treated with CHT/RT+S was 30 Gy (range, 30-50.4 Gy) delivered in a median of 10 fractions (range, 10-28 fractions) and 45 Gy (range, 30-45 Gy) in a median of 25 fractions (range, 10-25 fractions) for patients treated with CHT+CHT/RT+S. Esophagectomy was performed 6-8 weeks after completion of concurrent chemoradiotherapy. Most patients underwent transthoracic esophagectomy (n = 66, 82.5%). RESULTS: The pretreatment characteristics were well balanced between the two groups except for age. The median follow-up time was 29 months (22 months for the CHT/RT+S group and 38.5 months for the CHT+CHT/RT+S group) for all patients and 49 months for living patients. The actuarial overall survival (OS), disease-free survival (DFS), locoregional control (LRC), and distant metastasis-free survival (DMFS) rate at 5 years for the entire group was 46%, 36.6%, 70.7%, and 53.2%, respectively. Statistically significant differences in the OS, DFS, and LRC rates between the two groups were detected. Specifically, the 5-year OS rate was 22.8% and 71.1% in the CHT/RT+S and CHT+CHT/RT+S group (p = 0.0001), respectively. The 5-year DFS rate was 27.6% and 56.6% in the CHT/RT+S and CHT+CHT/RT+S group (p = 0.003), respectively. The 5-year LRC rate was 64.2% and 85.6% in the CHT/RT+S and CHT+CHT/RT+S group (p = 0.007), respectively. The difference in the DMFS rate between the two groups was statistically significant, with a 2- and 5-year actuarial rate of 63.9% and 51.9%, respectively, in the CHT/RT+S group and 76.9% and 74.1%, respectively, in the CHT+CHT/RT+S group (p = 0.04). The statistically significant differences persisted when patients who received >/=45 Gy in each group were compared. Among those patients, the 5-year OS, DFS, LRC, and DMFS rates were 23.1%, 15.4%, 58.6%, and 39.2%, respectively, for those receiving CHT/RT+S, and 71.4% (p = 0.001), 55.8% (p = 0.0008), 84.6% (p = 0.005), and 77.3% (p = 0.009), respectively, for those receiving CHT+CHT/RT+S. The pathologic complete response (pCR) rate was greater in the CHT+CHT/RT+S group compared with in the CHT/RT+S group (p = 0.008). In univariate analysis, young age, good Karnofsky performance status, Stage II disease, total radiation dose, multiple drug regimen for concurrent CHT, pCR, R0 resection, distant disease progression, and CHT+CHT/RT+S treatment proved to be prognostic factors for OS. Lower esophageal/gastroesophageal junction tumor location, pCR, R0 resection, and CHT+CHT/RT+S treatment were favorable prognostic factors for LRC. Neither the total radiation dose nor multiple drugs for concurrent CHT were negative prognostic factors for LRC. In multivariate analysis, pCR, R0 resection, and treatment with CHT+CHT/RT+S were independent positive predictive factors for OS, and distant recurrences were negative predictive factors for OS. R0 resection, CHT+CHT/RT+S treatment, and lower esophageal/gastroesophageal junction tumor location were positive predictive factors for LRC. The radiation dose was not identified as an independent prognostic factor for either OS or LRC in the multivariate analysis. Meaningful multivariate analysis could not be performed when the multiple drug vperformed when the multiple drug variable was included in the model because of the small number of patients. CONCLUSION: Significantly greater LRC, DFS, OS, and DMFS were found in patients treated with CHT+CHT/RT+S compared with those treated with CHT/RT+S. The pCR rate was significantly higher in the CHT+CHT/RT+S group. Induction CHT was an independent favorable prognostic factor for both LRC and OS for the population included in this study. Our data suggest that a randomized trial comparing CHT+CHT/RT+S and CHT/RT+S is warranted to assess further the merits of this treatment in patients with this currently very lethal cancer.

Adult↗

PubMed2004

Intrathoracic tumour motion estimation from CT imaging using the 3D optical flow method.

The purpose of this work was to develop and validate an automated method for intrathoracic tumour motion estimation from breath-hold computed tomography (BH CT) imaging using the three-dimensional optical flow method (3D OFM). A modified 3D OFM algorithm provided 3D displacement vectors for each voxel which were used to map tumour voxels on expiration BH CT onto inspiration BH CT images. A thoracic phantom and simulated expiration/inspiration BH CT pairs were used for validation. The 3D OFM was applied to the measured inspiration and expiration BH CT images from one lung cancer and one oesophageal cancer patient. The resulting displacements were plotted in histogram format and analysed to provide insight regarding the tumour motion. The phantom tumour displacement was measured as 1.20 and 2.40 cm with full-width at tenth maximum (FWTM) for the distribution of displacement estimates of 0.008 and 0.006 cm, respectively. The maximum error of any single voxel's motion estimate was 1.1 mm along the z-dimension or approximately one-third of the z-dimension voxel size. The simulated BH CT pairs revealed an rms error of less than 0.25 mm. The displacement of the oesophageal tumours was nonuniform and up to 1.4 cm, this was a new finding. A lung tumour maximum displacement of 2.4 cm was found in the case evaluated. In conclusion, 3D OFM provided an accurate estimation of intrathoracic tumour motion, with estimated errors less than the voxel dimension in a simulated motion phantom study. Surprisingly, oesophageal tumour motion was large and nonuniform, with greatest motion occurring at the gastro-oesophageal junction.

Algorithms↗

PubMed2004

Modelling 6 MV photon beams of a stereotactic radiosurgery system for Monte Carlo treatment planning.

The goal of this work is to build a multiple source model to represent the 6 MV photon beams from a Cyberknife stereotactic radiosurgery system for Monte Carlo treatment planning dose calculations. To achieve this goal, the 6 MV photon beams have been characterized and modelled using the EGS4/BEAM Monte Carlo system. A dual source model has been used to reconstruct the particle phase space at a plane immediately above the secondary collimator. The proposed model consists of two circular planar sources for the primary photons and the scattered photons, respectively. The dose contribution of the contaminant electrons was found to be in the order of 10(-3) of the total maximum dose and therefore has been omitted in the source model. Various comparisons have been made to verify the dual source model against the full phase space simulated using the EGS4/BEAM system. The agreement in percent depth dose (PDD) curves and dose profiles between the phase space and the source model was generally within 2%/1 mm for various collimators (5 to 60 mm in diameter) at 80 to 100 cm source-to-surface distances (SSD). Excellent agreement (within 1%/1 mm) was also found between the dose distributions in heterogeneous lung and bone geometry calculated using the original phase space and those calculated using the source model. These results demonstrated the accuracy of the dual source model for Monte Carlo treatment planning dose calculations for the Cyberknife system.

Models, Theoretical↗

PubMed2004

Dose and volume reduction for normal lung using intensity-modulated radiotherapy for advanced-stage non-small-cell lung cancer.

PURPOSE: To investigate dosimetric improvements with respect to tumor-dose conformity and normal tissue sparing using intensity-modulated radiotherapy (IMRT) compared with three-dimensional conformal radiotherapy (3D-CRT) for advanced-stage non-small-cell lung cancer (NSCLC). METHODS AND MATERIALS: Forty-one patients with Stage III-IV and recurrent NSCLC who previously underwent 3D-CRT were included. IMRT plans were designed to deliver 63 Gy to 95% of the planning target volume using nine equidistant coplanar 6-MV beams. Inverse planning was performed to minimize the volumes of normal lung, heart, esophagus, and spinal cord irradiated above their tolerance doses. Dose distributions and dosimetric indexes for the tumors and critical structures in both plans were computed and compared. RESULTS: Using IMRT, the median absolute reduction in the percentage of lung volume irradiated to >10 and >20 Gy was 7% and 10%, respectively. This corresponded to a decrease of >2 Gy in the total lung mean dose and of 10% in the risk of radiation pneumonitis. The volumes of the heart and esophagus irradiated to >40-50 Gy and normal thoracic tissue volume irradiated to >10-40 Gy were reduced using the IMRT plans. A marginal increase occurred in the spinal cord maximal dose and lung volume >5 Gy in the IMRT plans, which could be have resulted from the significant increase in monitor units and thus leakage dose in IMRT. CONCLUSION: IMRT planning significantly improved target coverage and reduced the volume of normal lung irradiated above low doses. The spread of low doses to normal tissues can be controlled in IMRT with appropriately selected planning parameters. The dosimetric benefits of IMRT for advanced-stage non-small-cell lung cancer must be evaluated further in clinical trials.

Adult↗

PubMed2004

Equivalent outcome of patients with clinical Stage IIIA non-small-cell lung cancer treated with concurrent chemoradiation compared with induction chemotherapy followed by surgical resection.

PURPOSE: To compare the outcome of induction chemotherapy followed by surgery (C/S) and concurrent chemoradiotherapy (CRT) for clinical Stage IIIA non-small-cell lung cancer (NSCLC). METHODS AND MATERIALS: Between 1990 and 2000, 107 patients underwent either induction C/S (n = 55) or concurrent CRT (n = 52) for clinical Stage IIIA NSCLC at The University of Texas M. D. Anderson Cancer Center. Patient and tumor characteristics were balanced in the two treatment groups with respect to T and N stage, race, median age, performance status, weight loss, and histologic findings. In the C/S group, induction chemotherapy included two to four cycles of cisplatin-based chemotherapy followed by lobectomy and mediastinal lymph node dissection. Postoperative RT was delivered in 35 patients, with referral for RT made at the discretion of the treating physician. CRT consisted of three cycles of cisplatin-based chemotherapy given every 3 weeks concurrent with RT to 60-63 Gy in 30-35 fractions in 27 patients and 69.6 Gy in 58 fractions (b.i.d.) in 25 patients. Local control, overall disease-free survival, and distant metastasis-free survival rates were calculated using the Kaplan-Meier method. The median follow-up duration was 20 months in all patients and 32 months in surviving patients. RESULTS: No statistically significant differences were found in the end points measured in the two treatment groups. Specifically, the median survival time was 31 and 27 months and the 5-year overall survival rate was 33% and 30% in the C/S and CRT groups, respectively. Likewise, the 5-year local control (58% vs. 61%), disease-free (24% vs. 23%), and distant metastasis-free (44% vs. 36%) survival rates in the two groups were not significantly different. In the C/S group, postoperative RT significantly improved the 5-year local control rate from 33.8% to 81.5% (p = 0.007) but did not significantly improve overall survival. Additionally, patients in the C/S group whose disease responded to induction chemotherapy had a significantly improved 5-year overall survival rate (50%) compared with those who had stable or progressive disease (16%, p = 0001). CONCLUSION: Treatment of Stage IIIA NSCLC using either induction C/S or CRT resulted in similar outcomes in terms of local control and median overall, 5-year overall, distant metastasis-free, and disease-free survival. However, patients undergoing induction C/S often needed postoperative RT to achieve local control equivalent to that achieved with concurrent CRT. Advances in radiation-based treatment as reflected in this study have resulted in similar outcomes compared with modern induction C/S. To improve survival, however, newer systemic agents that reduce and control distant metastasis are required.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2004

The utilization of a 3-dimensional noncoplanar treatment plan to avoid pacemaker complications.

Treatment planning of thoracic patients having upper lobe lesions and a pacemaker presents quite a challenge. It is necessary to avoid the pacemaker as well as other critical structures in order to deliver the prescribed dose for local control. This case demonstrates the utilization of noncoplanar beams and asymmetric fields to limit the radiation dose to the pacemaker. The dose to the pacemaker was quantified by the information represented in the dose-volume histogram (DVH) of the computerized tomography (CT)-based treatment plan. The delivered dose was verified utilizing thermoluminescent dosimeters (TLDs) placed on the patient. Measurements of the daily dose from all of the treatment fields to include the open jaws during portal imaging were taken to sum the total possible dose the pacemaker may receive. The allowable dose to the pacemaker is dependent upon individual manufacturers. It was found that with proper treatment planning and appropriate precautions, a patient is able to receive full-prescribed dose with no risks of interfering with the pacemaker function.

Aged↗

PubMedDate not supplied

Promising early local control of malignant pleural mesothelioma following postoperative intensity modulated radiotherapy (IMRT) to the chest.

PURPOSE: Malignant pleural mesothelioma often recurs locally in spite of aggressive resection by extrapleural pneumonectomy and conventional radiotherapy. This may be due to failure to recognize the extent of clinical target volume (CTV) or suboptimal dose delivery to a target that abuts the heart, esophagus, liver, lung, kidney, and spinal cord. We report how these geometric/dosimetric constraints were overcome by exploiting intensity-modulated radiotherapy in the first cohort patient. MATERIALS AND METHODS: Twenty-eight patients who had undergone extrapleural pneumonectomy were treated with intensity-modulated radiotherapy. The CTV included the surgically violated inner chest wall, insertion of diaphragm, pleural reflections, and deep margin of the incision. CTV delineation was facilitated by intraoperative radio-opaque marking. Motion was assessed. CTV doses were 45-50 Gy with boosts taken to 60 Gy. RESULTS: Despite the large, irregular CTV (median, 4151 cc; range, 2667-7286 cc), an average of 97% of the CTV was covered to the target dose (range, 92%-100%). Respiratory motion was minimal because of immobility of the prosthetic diaphragm. Normal tissue dose constraints were met. The commonest effects were nausea/vomiting (89%) and dyspnea (80%). Esophagitis was absent (59% of patients) or mild (34% grade 1/2). At median follow-up of 9 months (range, 5-27 months), local control within the contoured target was 100%. One-year survival, disease-specific survival, and disease-free survival are 65%, 91%, and 88%, respectively. CONCLUSIONS: Intensity-modulated radiotherapy after extrapleural pneumonectomy is tolerable and seems effective, at least at this early point. As local control improves, systemic metastases become more common, and it may be appropriate to add novel agents to further improve the therapeutic ratio.

Adult↗