Preference-based Comparative Study on Definitive Radiotherapy of Prostate Cancer With Protons

ProtoChoice-P is a prospective multicenter trial to evaluate proton therapy in patients suffering from prostate cancer. Primary aim of the study is a decrease of moderate or severe genito-urinary or intestinal side effects (Common Terminology Criteria for Adverse Events (CTCAE) 4.0 grade 2 or higher) by the use of proton therapy. Secondary endpoints contain assessment of quality of life, biochemical recurrence and recurrence free survival as well as overall survival and economic comparison between photon and proton therapy.

The hypothesis of the study is a 7.5% decrease of combined genito-urinary and intestinal side effects from 15% with photon therapy to 7.5% by the use of protons. With an alpha of 0.05 and 80% power it is therefore necessary to treat 131 patients with protons to detect such difference. With an estimated drop-out rate of 10% 146 patients have to be recruited to the proton arm. As randomization to photon or proton therapy is not possible in a multicenter setting with only few proton facilities available patients treated with photons will be prospectively matched to their proton counterparts. Stratification criteria will include: Age, high dose volume, androgen deprivation, history of surgery, obstructive disease, increased risk for rectal bleeding, socio-economic criteria and use of rectal balloon during radiotherapy. Comparison of the primary endpoint will be restricted to patients without irradiation of lymphatic drainage.