(S011) Hypofractionated vs Standard Fractionated Proton Beam Therapy for Early-Stage Prostate Cancer: Interim Results of a Randomized Prospective Trial

April 30, 2015

Patients tolerated proton therapy in this randomized trial well, with excellent QoL scores, persistent low IPSS, and no grade ≥ 3 AEs in either arm. Thus far, there is no apparent clinical difference in outcomes with hypofractionated proton beam therapy compared to standard fractionation.

William F. Hartsell, MD, Megan Dunn, PhD, Gary Larson, MD, Carlos Vargas, MD; CDH Proton Center; Proton Collaborative Group; ProCure Proton Center; Mayo Clinic

PURPOSE: After prostate cancer treatment, most adverse event (AE) and quality of life (QoL) changes can be initially identified within the first 2 years. The purpose of this interim analysis is to determine if there are differences in terms of QoL, International Prostate Symptom Score (IPSS), or AEs among prostate cancer patients treated on a randomized prospective trial with either standard fractionation or hypofractionation.

MATERIALS AND METHODS: Eighty-two patients were randomized to 38 Gy(relative biologic effectiveness [RBE]) in 5 treatments (n = 49) vs 79.2 Gy(RBE) in 44 treatments (n = 33). All patients had stage I prostate cancer and were treated with proton therapy using fiducial markers and daily image guidance.

RESULTS: Median follow-up for both groups was 18 months, with 33 patients reaching follow-up of 2 years or more. Patient characteristics for both groups were similar, with most patients being T1c (84%) and all having a Gleason score of 6 and a prostate-specific antigen (PSA) level < 10 ng/mL (median, 5.6 ng/mL). Baseline median IPSS was 5 for the 5-fraction arm (range: 0–15), and median IPSS was also 5 for the 44-fraction arm (range: 0–14). There was no difference between the two groups with regard to Expanded Prostate Index Composite (EPIC) urinary, bowel, or sexual function scores at 3, 6, 9, 12, 18, 24, or 36 months. The only significant difference was the IPSS score at 12 months: 5 for the 44-fraction arm vs 8 for the 5-fraction arm (P = .03), but there was no difference in the IPSS scores at the other time points. No grade ≥ 3 AEs were seen in either arm.

CONCLUSIONS: Patients tolerated proton therapy in this randomized trial well, with excellent QoL scores, persistent low IPSS, and no grade ≥ 3 AEs in either arm. Thus far, there is no apparent clinical difference in outcomes with hypofractionated proton beam therapy compared to standard fractionation.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org