Room: AAPM ePoster Library
Purpose: To thoroughly investigate the dosimetric impact of patient motion on the occurrence of radiation pneumonitis after radiation therapy for breast and esophageal cancer.
Methods: Totally 42 breast cancer patients and 94 esophageal cancer patients were investigated for radiation pneumonitis (RP) post radiation therapy. A retrospective study was performed to thoroughly investigate the dosimetric impact on the occurrence and volume of RP. First, the patients were divided into groups in terms of with or without concurrent chemotherapy and with or without applying respiratory management during radiation therapy. Then the dose distribution was calculated by incorporating the patient motion information that can be approximated based on cone beam computed tomography (CBCT) images before each fraction. The calculated fractional dose distributions were integrated to evaluate the dosimetric factors of RP such as V20, V5, V30 and mean dose of lung for all groups of patients. We performed the calculation using an in-house Monte Carlo software and compared the results with Eclipse (Varian Medical System).
Results: Dosimetric factors were verified to be significantly correlated to RP. Dose variation caused by the positional discrepancy between fractions and patient respiratory motion during treatment were related with the occurrence of RP. Monte Carlo method and Eclipse got a good agreement on dose distributions. Monte Carlo method demonstrated its superior robustness and flexibility on calculation in complex situations.
Conclusion: The application of respiratory motion control is an important factor to reduce the occurrence of radiation pneumonitis.