Restricted Field IMRT Dramatically Enhances IMRT Planning for Mesothelioma
Wednesday, September 26th, 2007.
International Journal of Radiation Oncology, Biology, Physics. 2007 Sep 22; [Epub ahead of print] [Link]
Allen AM, Schofield D, Hacker F, Court LE, Czerminska M.
Department of Radiation Oncology, Dana-Farber Cancer Institute, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA.
Abstract
Purpose: To improve the target coverage and normal tissue sparing of intensity-modulated radiotherapy (IMRT) for mesothelioma after extrapleural pneumonectomy.
Methods and Materials: Thirteen plans from patients previously treated with IMRT for mesothelioma were replanned using a restricted field technique. This technique was novel in two ways. It limited the entrance beams to 200° around the target and three to four beams per case had their field apertures restricted down to the level of the heart or liver to further limit the contralateral lung dose. New constraints were added that included a mean lung dose of <9.5 Gy and volume receiving ≥5 Gy of <55%.
Results: In all cases, the planning target volume coverage was excellent, with an average of 97% coverage of the planning target volume by the target dose. No change was seen in the target coverage with the new technique. The heart, kidneys, and esophagus were all kept under tolerance in all cases. The average mean lung dose, volume receiving ≥20 Gy, and volume receiving ≥5 Gy with the new technique was 6.6 Gy, 3.0%, and 50.8%, respectively, compared with 13.8 Gy, 15%, and 90% with the previous technique (p < 0.0001 for all three comparisons). The maximal value for any case in the cohort was 8.0 Gy, 7.3%, and 57.5% for the mean lung dose, volume receiving ≥20 Gy, and volume receiving ≥5 Gy, respectively.
Conclusion: Restricted field IMRT provides an improved method to deliver IMRT to a complex target after extrapleural pneumonectomy. An upcoming Phase I trial will provide validation of these results.
Keywords: Intensity-modulated radiotherapy, IMRT, Mesothelioma, Optimization
Glossary
- oncology
- (on-call-o-jee) the branch of medicine concerned with the diagnosis and treatment of cancer.
- cancer
- malignancy; a group of diseases typified by abnormal, generally out-of-control, cell growth.
- tissue
- a collection of cells, united to perform a particular function.
- mesothelioma
- a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.
- IMRT
- (intensity-modulated radiation therapy) an advanced mode of high-precision radiotherapy that utilizes computer-controlled x-ray accelerators to deliver thin beams of radiation of different strengths (beams of modulating intensity) directly to the tumor from many angles. Higher and more effective radiation doses can safely be delivered to tumors with fewer side effects as compared to conventional radiotherapy techniques. Even when doses are not increased, IMRT can potentially reduce treatment toxicity.
- extrapleural pneumonectomy
- (EPP) surgery to remove the pleura, diaphragm, pericardium, and entire lung involved with the tumor. You can view a web cast from Brigham and Women's Hospital in Boston of this procedure being done by Dr. David Sugarbaker: see the extrapleural pneumonectomy (EPP) web cast here.
