Safety and Efficacy Study of Neoadjuvant Radiohormonal Therapy for Oligometastatic Prostate Cancer: Protocol of an Open-Label, Dose-Escalation, Single-Centre Phase I/II Clinical Trial

BACKGROUND: The optimal treatment for oligometastatic prostate cancer (OMPC) is still on its way. Accumulating evidence has proven the safety and feasibility of radical prostatectomy and local or metastasis-directed radiotherapy for oligometastatic patients. The aim of this trial is to demonstrate the safety and feasibility outcomes of metastasis-directed neoadjuvant radiotherapy (naRT) and neoadjuvant androgen deprivation therapy (naADT) followed by robotic-assisted radical prostatectomy (RARP) for treating OMPC. METHODS: The present study will be conducted as a prospective, open-label, dose-escalation, phase I/II clinical trial. The patients with oligometastatic PCa will receive 1 month of naADT, followed by metastasis-directed radiation and abdominal or pelvic radiotherapy. Then, radical prostatectomy will be performed at intervals of 4-8 weeks after radiotherapy, and ADT will be continued for 2 years. The primary endpoints of the study are safety profiles, assessed by the Common Terminology Criteria for Adverse Events (CTCAE) 5.0 grading scale, and perioperativemorbidities, assessed by the Clavien-Dindo classification system. The secondary endpoints include positive surgical margin (pSM), biochemical recurrence-free survival (bPFS), radiological progression-free survival (RPFS), postoperative continence, and quality of life (QoL) parameters. DISCUSSION: The optimal treatment for OMPC is still on its way, prompting investigation for novel multimodality treatment protocol for this patient population. Traditionally, radical prostatectomy has been recommended as one of the standard therapies for localized prostate cancer, but indications have expanded over the years as recommended by NCCN and EAU guidelines. RP has been carried out in some centres for OMPC patients, but its value has been inconclusive, showing elevated complication risks and limited survival benefit. Neoadjuvant radiotherapy has been proven safe and effective in colorectal cancer, breast cancer and other various types of malignant tumors, showing potential advantages in terms of reducing metastatic stem-cell activity, providing clinical downstaging, and reducing potential intraoperative risks. Existing trials have shown that naRT is well tolerated for high-risk and locally-advanced prostate cancer. In this study, we hope to further determine the optimal irradiation dose and patient tolerance for genitourinary, gastrointestinal and systemic toxicities with the design of 3+3 dose escalation; also, final pathology can be obtained following RP to further determine treatment response and follow-up treatment plans. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR1900025743. http://www.chictr.org.cn/showprojen.aspx?proj=43065.