Safety and quality of life of PSMA-PET- and MRI-based focal dose escalated radiotherapy for intermediate- and high-risk prostate cancer: Primary endpoint analysis of the bi-centric phase II HypoFocal trial (ARO2020-01)

Background and Purpose: To present the primary endpoint results, toxicities and quality of life (QoL) after two-year follow-up (FU) of the HypoFocal Phase II trial. Material and Methods: Intermediate- and high-risk prostate cancer (PCa) patients were treated with moderately hypofractionated radiotherapy (MHRT) of 60 Gy in 20 fractions and a focal-boost of up to 75 Gy in Arm A, or high-dose-rate-brachytherapy (HDR-BT) of 15 Gy to the whole-gland with a boost of up to 19 Gy, followed by external beam RT (EBRT) of 44 Gy in 20 fractions in Arm B. Boost was based on combined information by multiparametric-magentic-resonance-tomography (mpMRI) and positron-emission-tomography targeting prostate-specific-membrane-antigen (PSMA-PET). Genitourinary (GU) and gastrointestinal (GI) toxicities were assessed according to CTCAEv5.0. QoL was assessed with validated questionnaires (IPSS, QLQ-PR25 and QLQ-PR30). Results: Twenty-five patients were treated with MHRT and 30 patients with HDR-BT + EBRT. At two-year-FU, the rate of grade 2 + GU and GI toxicity was 24 % and 8 % in Arm A and 10 % and 0 % in Arm B, respectively. Two grade 3 GI toxicities were reported in Arm A, which can be attributed to multifactorial genesis and interventions. QoL was good with significant and minimally-important-differences only in bowel symptoms in Arm A and sexual functioning in Arm B. One patient in each arm relapsed. Limitations are the relatively small sample size. Conclusion: This is the first trial do demonstrate safety and feasibility of focal dose-escalation based on mpMRI and PSMA-PET in MHRT and HDR-BT + EBRT in intermediate- and high-risk PCa. Particularly, HDR-BT offers good toxicity and QoL profiles. Radiation proctitis demands careful management.