Breast-Sparing Proton Therapy for Hodgkin's Disease

According to the National Cancer Institute's Surveillance, Epidemiology, and End Results Program, there will be an estimated 8,490 new cases of Hodgkin's Lymphoma (HL) in the United States in 2010, with an estimated 1,320 deaths (Jemal, Siegel et al.). The unadjusted rates of 5 year overall survival are approximately 95%, and remain among the highest of all childhood and adult malignancies. With many children and young adults surviving into advanced age, the impetus has been to develop less toxic yet equally effective treatments. One of the main approaches taken over the last 25 years to minimize long-term treatment toxicity has been to limit the amount and volume of radiation received by patients. This pilot study continues along those lines, attempting to further refine the delivery of radiation therapy (RT) in order to avoid one of the most notorious long-term side-effects: secondary breast cancer. Multiple studies investigating late toxicity in long-term survivors of pediatric Hodgkin's Lymphoma have shown the risk of breast cancer in young females receiving mediastinal radiation to be 50 times greater than their age-matched counterparts. The Late Effects Study Group, with a median follow-up of 17 years, reported a breast cancer incidence of 16% with a standardized incidence ratio of 55.5 (Bhatia, Yasui et al. 2003). Through utilization of breast-sparing proton therapy, we hope to provide young female patients with the benefits of radiation therapy while decreasing their risk of secondary breast cancer, thus increasing the therapeutic ratio. In a prior computer-based, in-silico, dose planning study, utilizing the most basic beam orientation (a single PA beam), we showed that dose to breast tissue was reduced by a minimum of at least 80% with proton treatment compared to standard AP-PA photon treatment (in publication). Furthermore, dose to clinical target volume was maintained, and dose to other normal structures was statistically no worse. We now aim to validate these findings by verifying the beam range, in-vivo, via post-treatment combined Positron Emission Tomography-Computer Tomography (PET-CT) imaging in young females undergoing supra-diaphragmatic radiotherapy for Hodgkin's Disease.