389 Background: The liver is one of the most radiosensitive organs, making radiation therapy (RT) for liver tumors extremely challenging. RT is appropriate only for a minority of liver patients with limited tumor burden; a reduction in the prescribed radiation dose may be needed to lower the probability of radiation-induced liver disease especially in the presence of cirrhosis. Proton beam therapy (PBT) delivers less dose to the liver than photon therapy and is expected to reduce toxicity while also permitting safe dose escalation for some patients with liver tumors. Methods: The Proton Collaborative Group REG001-09 trial (NCT01255748) prospectively collects data for PBT patients with a variety of cancer types. To better understand treatment details and outcomes associated with liver PBT, patients enrolled on the PCG registry trial from 5 institutions who received liver PBT for any cancer between 2012 and 2016 were analyzed. Results: A total of 43 liver cancer patients were included, most with hepatocellular carcinoma (48.8%) or cholangiocarcinoma (25.6%). The vast majority did not have surgery at any time (86%). Most were treatment naive prior to PBT; 2 previously had RT and 8 had prior chemotherapy (mostly cholangiocarcinoma patients). The median total prescribed PBT dose was 58.05 Gy(RBE) (range 21.7-67.5). The median number of prescribed fractions was 15 (range 12-37). PBT was delivered to only the liver in 90.7% of patients; inclusion of lymph nodes was rare. Uniform scanning was used in 26 (72.1%) and pencil beam scanning in 2 patients (4.7%); the delivery technique used for the remaining patients was unknown (23.2%). With median follow up of 4.4 months (range 1.3-17.9), 3 patients (7%) had an intrahepatic recurrence, 2 patients (4.6%) developed distant metastasis, and 10 patients (23.3%) died. No grade 3 or higher toxicity was reported although 17 patients (39.5%) had grade 2 toxicity predominantly fatigue, anorexia, nausea, or vomiting. Conclusions: Although longer follow up is needed to assess late toxicities as well as disease control, early outcomes from the PCG registry trial for liver cancer patients shows that predominantly hypofractionated PBT has a very favorable acute toxicity profile.
Treatment interruptions affect biochemical failure rates in prostate cancer patients treated with proton beam therapy: Report from the multi-institutional proton collaborative group registry
