Late toxicity for prostate cancer patients treated with hypofractionated helical tomotherapy.

Abstract

The purpose of this study is to evaluate the long term tolerability of hypofractionated helical tomotherapy (HT) in localized prostate cancer patients. Previous hypofractionated schedules with conventional RT were associated with excessive toxicity, likely due to inadequate sophistication of treatment delivery. There are few data about late toxicity after HT. We evaluated 38 patients with primary adenocarcinoma of the prostate. There were 9 (24%), 15 (39%), and 14 (37%) patients with high, intermediate, and low risk, respectively. Patients were treated with hypofractionated HT from May 2008 to February 2011. Hypofractionation regimens included: 68.04Gy at 2.52Gy/fraction (N=25; 66%), 70Gy at 2.5Gy/fraction (N=4; 11%) and 70.2Gy at 2.6Gy/fraction (N=9; 23%). Late genitourinary (GU) and gastrointestinal (GI) toxicity was scored using the Radiation Therapy Oncology Group scoring system. Median age at diagnosis was 70 years (range 49-80) and median follow-up, 5.8 years. Late grade 1, 2 and 3 GI toxicity were 13%, 24%, and 2.6%, respectively. Late grade 1, 2, 3 GU toxicity were 29%, 21%, and 8%, respectively. Sexual toxicity was evaluated in 19 patients to be grade 1, 2 in 11% and grade 3 in 16%. Multivariate analysis showed that patients with higher values of rectum V50 associated with late GI toxicity (P=0.025). Patients with PSA ≤8 (P=0.048) or comorbidities (P=0.013) at diagnosis were associated with higher late GU toxicity. Additionally, PSA ≤8 also associated with moderate (grade ≥2) late GU toxicity in the multivariate analysis (P=0.028). Hypofractionated HT can be delivered safely with limited rates of moderate and severe late toxicity. The proportion of the rectum that receives a moderate and high dose, having comorbidities, and PSA at diagnosis seem to associate with long term toxicity.