Mohan Suntharalingam

Clinical implementation of intensity-modulated arc therapy.

PURPOSE Intensity-modulated arc therapy (IMAT) is a method for delivering intensity-modulated radiation therapy (IMRT) using rotational beams. During delivery, the field shape, formed by a multileaf collimator (MLC), changes constantly. The objectives of this study were to (1) clinically implement the IMAT technique, and (2) evaluate the dosimetry in comparison with conventional three-dimensional (3D) conformal techniques. METHODS AND MATERIALS Forward planning with a commercial system (RenderPlan 3D, Precision Therapy International, Inc., Norcross, GA) was used for IMAT planning. Arcs were approximated as multiple shaped fields spaced every 5-10 degrees around the patient. The number and ranges of the arcs were chosen manually. Multiple coplanar, superimposing arcs or noncoplanar arcs with or without a wedge were allowed. For comparison, conventional 3D conformal treatment plans were generated with the same commercial forward planning system as for IMAT. Intensity-modulated treatment plans were also created with a commercial inverse planning system (CORVUS, Nomos Corporation). A leaf-sequencing program was developed to generate the dynamic MLC prescriptions. IMAT treatment delivery was accomplished by programming the linear accelerator (linac) to deliver an arc and the MLC to step through a sequence of fields. Both gantry rotation and leaf motion were enslaved to the delivered MUs. Dosimetric accuracy of the entire process was verified with phantoms before IMAT was used clinically. For each IMAT treatment, a dry run was performed to assess the geometric and dosimetric accuracy. Both the central axis dose and dose distributions were measured and compared with predictions by the planning system. RESULTS By the end of May 2001, 50 patients had completed their treatments with the IMAT technique. Two to five arcs were needed to achieve highly conformal dose distributions. The IMAT plans provided better dose uniformity in the target and lower doses to normal structures than 3D conformal plans. The results varied when the comparison was made with fixed gantry IMRT. In general, IMAT plans provided more uniform dose distributions in the target, whereas the inverse-planned fixed gantry treatments had greater flexibility in controlling dose to the critical structures. Because the field sizes and shapes used in the IMAT were similar to those used in conventional treatments, the dosimetric uncertainty was very small. Of the first 32 patients treated, the average difference between the measured and predicted doses was -0.54 +/- 1.72% at isocenter. The 80%-95% isodose contours measured with film dosimetry matched those predicted by the planning system to within 2 mm. The planning time for IMAT was slightly longer than for generating conventional 3D conformal plans. However, because of the need to create phantom plans for the dry run, the overall planning time was doubled. The average time a patient spent on the table for IMAT treatment was similar to conventional treatments. CONCLUSION Initial results demonstrated the feasibility and accuracy of IMAT for achieving highly conformal dose distributions for different sites. If treatment plans can be optimized for IMAT cone beam delivery, we expect IMAT to achieve dose distributions that rival both slice-based and fixed-field IMRT techniques. The efficient delivery with existing linac and MLC makes IMAT a practical choice.

Comparison of three treatment options for single brain metastasis from lung cancer

Whole brain radiotherapy (WBRT), stereotactic radiosurgery (SRS), and the combination of both treatment methods were used for the management of single brain metastasis from lung cancer. The purpose of this study is to compare these three different treatment options in terms of local response, survival, and quality of life. From June 1995 to July 1998, 70 lung cancer patients with new diagnosed single brain metastasis were treated with either WBRT alone (n = 29), or SRS alone (n = 23), or the combination of both methods (n = 18). Multiple endpoints, including survival, freedom from local progression (FFLP), freedom from new brain metastasis (FFNBM), local control, Karnofsky performance status (KPS), and causes of death, were measured from the date of treatment completion and compared using univariate and multivariate analyses. For patients treated with WBRT‐alone, SRS‐alone, and SRS+WBRT, the median survivals were 5.7, 9.3, and 10.6 months, the median FFLP were 4.0, 6.9, and 8.6 months, the median FFNBM were 4.1, 6.7, and 8.6 months, and the local response rates were 55.6, 87.0, and 88.9%, respectively. Four of the 29 patients treated with WBRT‐alone continued with progression of disease. The post treatment KPS showed improvement in 41.4, 82.6, and 88.9% of patients treated with WBRT‐alone, SRS‐alone, and SRS+WBRT, respectively. The progression of new and/or recurred metastatic brain tumor as the cause of death accounted for 51.7%, 50.0%, and 28.3% of the patients treated with WBRT‐alone, SRS‐alone, and SRS+WBRT, respectively. Univariate analyses showed that the significant differences among the three treatment arms were observed based on all of the above mentioned endpoints. However, the comparison between SRS‐alone and SRS+WBRT groups indicated that adding WBRT only improves FFNBM (P = 0.0392). Cox regression analyses revealed no significant difference in both of the KPS (P = 0.1082) and causes of death (P = 0.081) among the three arms. Both SRS alone and SRS+WBRT seem better in prolonging life and improving quality of life than WBRT alone for patients with single brain metastasis from lung cancer. But the combined therapy did not show significant advantage over SRS alone in improving survival, enhancing local control, and quality of life except for a more favorable FFNBM. Further investigation via a randomized trial is needed to access the value of adding WBRT to SRS in the management of this group of patients. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 37–45 (2000).

The use of carboplatin and paclitaxel with daily radiotherapy in patients with locally advanced squamous cell carcinomas of the head and neck

PURPOSE Unresectable squamous cell carcinomas of the head and neck (SCCHN) continue to pose a significant therapeutic challenge. This report defines the toxicities, efficacy, and prognostic factors associated with the combination of carboplatin (CBDCA), paclitaxel, and once-daily radiation for patients with locally advanced disease. Additionally, the pharmacokinetics of paclitaxel were investigated. METHODS AND MATERIALS From 1993-1998, 62 patients with Stage III-IV SCCHN were treated with 70.2 Gy of RT at 1.8 Gy/fraction/day to the primary site. Weekly chemotherapy was given during RT consisting of paclitaxel (45 mg/m(2)/wk) and CBDCA (100 mg/m(2)/wk). All patients presented with locally advanced disease; 77% had T4 disease and 21% had T3 disease. Fifty-eight percent had N2b-N3 disease. RESULTS Sixty patients were evaluable for response and survival with a median follow-up of 30 months (range 7-70). Ninety-eight percent of patients completed prescribed therapy. One patient died after refusing medical management for pseudomembranous colitis and is scored as a Grade 5 toxicity. Two patients suffered Grade 4 leukopenia. Median number of break days was two. A clinical complete response (CR) at the primary site was obtained in 82%, with a total (primary site and neck) CR rate of 75%. The median survival for the entire cohort is 33 months. Response to therapy and status of the neck at presentation were the only prognostic factors found to influence survival. The median survival for patients who attained a CR is 49 months versus 9 months in those who did not attain a CR (p < 0.0001). The 2- and 3-year overall survival for complete responders are 79% and 61%. Plasma paclitaxel concentrations in the range shown to be radiosensitizing were achieved. CONCLUSIONS Weekly carboplatin and paclitaxel given concurrently with definitive once-daily external beam radiation therapy is well tolerated with over 90% of patients completing prescribed therapy. An ultimate CR rate of greater than 70% was obtained, which translated directly into improved survival. With 48% 3-year overall survival for the entire group, this regimen is an excellent option for this group of patients with a historically poor prognosis.

The national practice for patients receiving radiation therapy for carcinoma of the esophagus: Results of the 1996–1999 Patterns of Care Study

PURPOSE A Patterns of Care Study (PCS) was conducted to evaluate the standards of practice for patients receiving radiation therapy for esophageal cancer from 1996 to 1999. This study examined the evaluation and treatment schemes used during this time and compared these results to the PCS data obtained between 1992 and 1994 to identify any fundamental changes in national practice. METHODS A national survey was conducted using a two-stage cluster sampling technique. Specific information was collected on 414 patients with esophageal cancer who received radiotherapy (RT) as part of definitive or adjuvant management at 59 institutions. Patients were staged according to the 1983 AJCC. Eligibility criteria for case review included RT between 1996 and 1999, no evidence of distant metastasis (including CT evidence of either supraclavicular or celiac nodes >1 cm), squamous cell or adenocarcinoma histology, Karnofsky performance status >60, tumors in the thoracic esophagus with <2 cm extension into the stomach, and no prior malignancies within the last 5 years. Statistical analysis was performed on the database using SUDAAN software to accurately reflect the type of sampling technique used by PCS. For the purpose of this analysis, institutions were stratified as either large or small based on the number of new cases seen each year. For the purposes of comparison, the 1992-1994 PCS esophageal survey results were subjected to the same statistical procedures and tests. RESULTS The median age of patients was 64 years. Seventy-seven percent were male, and 23% were female. Karnofsky performance status was >or=80% in 85% of patients. The racial profile mirrors the previous survey with 75% Caucasian, 21% African-American, 3% Asian, and <1% Hispanic. A review of the histology revealed a nearly 50:50 split between squamous cell and adenocarcinoma. Sixteen percent were clinical Stage I, 39% clinical Stage II, and 33% clinical Stage III according to the 1983 AJCC system. Workup included endoscopy (96%), CT of the chest (87%), CT of the abdomen (75%), and esophagram (64%). Endoscopic ultrasound (EUS) was used in 18% of cases as compared to <2% in the original survey (p < 0.0001). Patients treated at large centers were more likely to undergo EUS than those treated at small centers (23% vs. 12%, p = 0.047). Fifty-six percent of patients received concurrent chemoradiation as definitive treatment. There was a significant increase in the use of concurrent chemoradiation before planned surgical resection as compared to the original survey (27% vs. 10%, p = 0.007). Other schemes included RT alone (10%), postoperative RT (1%), and postoperative chemoradiation (5%). Forty-six percent of patients with adenocarcinoma underwent trimodality therapy as compared to 19% with squamous cell carcinomas (p = 0.0002). Patients undergoing preoperative chemoradiation were more likely to have had an EUS. The median total dose of external RT was 50.4 Gy, and the median dose per fraction was 1.8 Gy. Brachytherapy was used in 6% of cases. The chemotherapy agents most commonly used included 5-fluorouracil (82%), cisplatin (67%), and paclitaxel (22%). Paclitaxel was more commonly employed as part of a preoperative chemoradiation regimen than in the setting of definitive chemoradiation (46% vs. 12%, p = 0.03). Compared to the original survey, paclitaxel use significantly increased between 1996 and 1999 (0.2% vs. 22%, p = 0.001). CONCLUSIONS The Patterns of Care Survey confirms the use of concurrent chemoradiation as part of the national standards of practice for the management of esophageal cancer patients. A comparison with the previous study documents the significant rise in the use of EUS, preoperative chemoradiation followed by surgery, and the increasing use of paclitaxel as part of a combined modality regimen.

Safe pulmonary resection after chemotherapy and high-dose thoracic radiation

BACKGROUND Pulmonary resection after high-dose thoracic irradiation is reported to be associated with a high morbidity and mortality, and has been considered to be prohibitive. METHODS We report safe pulmonary resection in 19 consecutive patients receiving neoadjuvant therapy that included greater than 59 Gy thoracic radiation. The mean thoracic radiation dose was 61.8 Gy (range 59.5-66.5) and mean age was 52 years (range 36-72 years). Cell type was adenocarcinoma (6), squamous (7), and other non-small cell lung cancer (NSCLC) (6). Sixteen of 19 patients received concurrent chemotherapy. Median time from end of treatment to surgical resection was 89 days (range 22-258 days). Surgical resection included 13 lobectomies and six pneumonectomies (four right, two left). RESULTS A complete pathologic response was seen in 8 of 19 (42%) patients. Three patients required intraoperative transfusion of blood. Mean intensive care unit stay was 2.0 days (range 1-8 days), and mean length of stay (LOS) was 8.0 days (range 3-18 days). There were four postoperative complications; one bronchopulmonary fistula, one subarachnoid-pleural fistula, and 2 patients with prolonged atelectasis. There was no incidence of acute respiratory distress syndrome (ARDS) or operative mortality. CONCLUSIONS Pulmonary resection, including pneumonectomy, after chemotherapy and high-dose thoracic radiation may be performed safely with a low rate of intraoperative and postoperative complications.

Single-fraction radiotherapy versus multifraction radiotherapy for palliation of painful vertebral bone metastases-equivalent efficacy, less toxicity, more convenient: a subset analysis of Radiation Therapy Oncology Group trial 97-14.

The Radiation Therapy Oncology Group (RTOG) trial 97‐14 revealed no difference between radiation delivered for painful bone metastases at a dose of 8 gray (Gy) in 1 fraction (single‐fraction radiotherapy [SFRT]) and 30 Gy in 10 fractions (multifraction radiotherapy [MFRT]) in pain relief or narcotic use 3 months after randomization. SFRT for painful vertebral bone metastases (PVBM) has not been well accepted, possibly because of concerns about efficacy and toxicity. In the current study, the authors evaluated the subset of patients that was treated specifically for patients with PVBM.

Outcome Results of the 1996-1999 Patterns of Care Survey of the National Practice for Patients Receiving Radiation Therapy for Carcinoma of the Esophagus

Purpose A Patterns of Care Study of patients treated from 1996 to 1999 evaluated the national practice for patients receiving radiation therapy for carcinoma of the esophagus in the United States. Methods A national survey was conducted at 59 institutions in a stratified random sample selected from a master list of radiation therapy facilities throughout the United States. Patient, tumor, and treatment characteristics were evaluated. Multivariate comparisons of survival times were made using the Cox proportional hazards model. Results Adenocarcinoma was diagnosed in 51% of patients and squamous cell carcinoma in 49% of patients. Sixteen percent of patients were clinical stage (CS) I (using the 1983 American Joint Committee on Cancer system), 39% were CS II, and 33% were CS III. Significant variables in the multivariate analysis of survival times included clinical stage, treatment approach, and facility size. Patients with CS III disease had a higher hazard risk of death as compared with CS I patients (haz...

Extracranial Stereotactic Radiation Delivery: Expansion of Technology Beyond the Brain

The development of improved immobilization systems, and a greater understanding of the radiobiologic considerations associated with stereotactic radiotherapy has recently led to the clinical implementation of this technology to extracranial sites. The shared principles of targeting and treatment delivery has led to a greater understanding of the potential role this therapy may have in the management of extracranial disease. This article will review, the radiobiologic considerations and the basic principles of physics and dosimetry that help govern the utilization of extracranial stereotactic radiotherapy. In addition, this article will summarize the data that exists in the literature to date, that has documented the rationale, and efficacy of this novel therapeutic approach.

Impact of early percutaneous endoscopic gastrostomy tube placement on nutritional status and hospitalization in patients with head and neck cancer receiving definitive chemoradiation therapy

This study analyzed the impact of timing of percutaneous endoscopic gastrostomy (PEG) tube placement on clinical endpoints in patients undergoing concurrent chemoradiation therapy (CRT).

Predictors of response and survival after concurrent chemotherapy and radiation for locally advanced squamous cell carcinomas of the head and neck

The objective of this study was to determine prognostic factors for response and survival on three consecutive institutional trials utilizing concurrent chemotherapy and radiation for locally advanced squamous cell carcinomas of the head and neck (SCCHN).