97 Background: Although there are many patterns of treatment in localized prostate caner, proton beam therapy has no definite role in them. We aimed to assess the outcomes of proton beam therapy (PBT) alone for patients with intermediate- and high-risk prostate cancer, and to clarify the role of PBT in the treatments. Methods: Between Jan. 2011 and Sep. 2014, 204 patients with intermediate- and high-risk prostate cancer who declined to receive hormonal treatments until biochemical or clinical recurrence were enrolled in the study. All patients were irradiated a 70-78 GyE in 28-39 fractions, and pre-treatment risk groups were classified in accordance with the D’Amico criteria. The 5-year (biochemical or clinical) recurrence-free survival (RFS), late gastrointestinal (GI) and genitourinary (GU) toxicity (NCI-CTCAE ver.4.0) were evaluated. We conducted a survey on sexual quality of life (QOL) every six months to evaluate any long-term damage to the sexual function using the Expanded Prostate Cancer Index Composite (EPIC). Results: The mean age and the follow-up period were 66 (range: 39-86) and 52 months (range: 24-76 months), respectively. The 5-year RFS rates in intermediate- (n = 112) and high- (n = 92) risk groups were 96.9% and 83.4%, respectively. There was a significant difference between the two groups (p = 0.002). The incidence of grade 2+ GI and GU toxicity were 4% and 3%, respectively. We found a significant difference in the GI toxicity between the two radiation protocols of 78GyE/39fractions (n = 6, 11%) and 70GyE/28fractions (n = 0, 0%) (p < 0.01). A 5.8% decrease in average after adjusting for aging was found in sexual summary score in six years after treatment, which was equivalent to aging of three years. Conclusions: Proton beam therapy alone demonstrated favorable results in patients with intermediate- and high-risk prostate cancer. Although more patients and longer follow-up are necessary to confirm the outcomes, these results suggested a hypothesis that proton beam therapy might not require androgen deprivation therapy in the treatment of localized prostate cancer, which could lead to a possibility of preserving of sexual function. Clinical trial information: MPTRC-N2 and N3.
Proton Beam Therapy Alone for Intermediate- or High-Risk Prostate Cancer: An Institutional Prospective Cohort Study
