For patients with non-metastatic prostate carcinoma, surgery or radiotherapy with or without hormonal therapy (HT) are curative treatment options. After prostatectomy, irradiation can be performed as adjuvant therapy or after prostate specific antigen (PSA) rise. While several larger studies reported on the oncological benefit for postoperative radiotherapy [
1,
2], there is only one prospective phase III trial evaluating the role of dose-escalated salvage irradiation so far [
3]. One multicenter, prospective phase II study from Germany is currently analyzing the role of moderately dose-escalated salvage radiotherapy in combination with local hyperthermia [
4].
For some years now, hypofractionated irradiation becomes more and more common for patients with prostate cancer. Many trials observed excellent clinical outcome after moderate hypofractionation for patients undergoing definitive radiotherapy [
5‐
8]. As one of the largest studies, the CHHiP trial evaluated 3216 men with localized prostate cancer. With a median follow-up of 62.4 months, hypofractionated radiotherapy (hRT) with 60 Gy in 20 fractions was not inferior compared to conventional fractionation. At 5 years, 90.6% in the 60 Gy group and 88.3% in the 74 Gy group were free of biochemical or clinical failure [
5]. Nowadays, hypofractionation is frequently proclaimed as the “new standard of care” for definitive radiotherapy of patients with prostate cancer. However, in the postoperative setting reliable data is missing with regard to hypofractionation. Few studies with mostly small numbers of patients reported on feasibility and toxicity. When using moderate hRT, postoperative radiotherapy seems to be safe and provided promising clinical results [
9‐
11]. Lewis et al. observed no acute grade 3 toxicity and a 4-year bPFS of 75% in a cohort of 56 men. All patients obtained image-guided intensity-modulated radiation therapy (IMRT) in 2.5 Gy fractions [
12]. Our institution also tested different approaches for hypofractionation after surgery: The PRIAMOS 1 trial evaluated treatment safety and toxicity of hRT of the prostate bed using IMRT and daily image-guidance. In this prospective phase II trial, 40 men received adjuvant or salvage irradiation with single doses of 3.0 Gy up to a total dose of 54.0 Gy. Treatment was tolerated well with no recorded side effects grade 3+ [
13]. Very similar results were obtained when using proton therapy instead of photons. With the use of protons, patient-reported bowel-score according to EORTC QLQ-PR25 questionnaire was already improved at week 10 and reached borderline significance when compared to photon therapy [
data unpublished]. Therefore, larger and randomized trials are of great interest evaluating the role of hRT for patients after prostatectomy.
The PAROS trial is designed as a prospective, multicenter and randomized 3-arm phase III trial evaluating toxicity and efficacy of hypofractionation for prostate cancer patients undergoing adjuvant or salvage irradiation.