Risk of Radiation-Induced Cardiotoxicity and Secondary Cancers in Hodgkin's Lymphoma Patients
A Toltz1*, N Shin1, C Laude2, D Roberge3, C Freeman2, J Seuntjens1, W Parker1, (1) McGill University, Montreal, QC, (2) McGill University Health Centre, Montreal, QC, (3) Centre Hospitalier de l'Université de Montréal, Montreal, QCTH-C-213AB-6 Thursday 10:30:00 AM - 12:30:00 PM Room: 213AB
Purpose: To evaluate the potential reduction of risk of late radiation-induced effects for young patients with Hodgkin's lymphoma treated with intensity modulated proton therapy (IMPT) as compared to 3D conformal involved-field photon radiotherapy. The late effects considered were cardiac mortality and secondary cancer in the lungs and breasts (for female patients).
Methods: Patient data was acquired for eleven patients who were under thirty years of age and were treated with radiotherapy for Hodgkin's lymphoma in Quebec in 2010. The original CT simulation images were used to re-plan the patients with IMPT using commercially-available treatment planning software. The contours of the critical organs of interest were reviewed for each patient by a physician and modified when necessary for consistency. The dose-volume matrices of the original photon plans and the new proton plans were analyzed using radiobiological models to assess the risk of late effects. The relative seriality model was utilized to predict excess risk of fatal cardiotoxicity. The organ equivalent dose concept was utilized in conjunction with a modified linear quadratic model to predict the excess absolute risk for induction of lung cancer and breast cancer. Parameters for each model were derived from retrospective studies in the literature.
Results: Mean excess risk of fatal cardiotoxicity was 0.9% for photon plans and 0.6% for proton plans. Mean excess absolute risk of developing lung cancer thirty years post-treatment was 11.9/10,000 patients per year (PY) for photons and 6.9/10,000 PY for protons. Mean excess absolute risk of developing breast cancer thirty years post-treatment was 6.0/10,000 PY for photons and 2.1/10,000 PY for protons.
Conclusions: IMPT has the potential to reduce the risk of fatal, radiation-induced late cardiotoxicity as well as the risk of radiation-induced secondary cancers in the lungs and breasts of young patients receiving radiotherapy for Hodgkin's lymphoma.