Phase II Trial to Investigate the Benefit of Elective Para-Aortic Radiotherapy (PART) for pN1 Prostate Cancer Using Arc Therapy (IMAT/VMAT)

Rationale: In prostate cancer with histopathologically proven pelvic lymph node metastasis (pN1) after extended pelvic lymph node dissection, multimodality treatment consisting of treatment of the primary tumor, androgen deprivation therapy and whole pelvic radiotherapy offers the best results and is the standard-of-care. However, in case >1 pelvic lymph node is invaded by tumor, after extended pelvic lymph node dissection, 40% of the patients relapse biochemically and clinically. Clinical relapse is present in the para-aortic lymph nodes (M1a disease) in 25% of the cases as we observed in series. Therefore Elective Para-Aortic Radiotherapy (PART) may improve disease control.

Objective: The main goal of this phase II study is to investigate whether elective para-aortic radiotherapy increases the clinical relapse-free survival (cRFS) defined as the absence of clinical relapse (cR) at biological imaging at 5 years. The secondary objectives of this study are: acute toxicity, late toxicity, quality of life (QoL), time to palliative androgen deprivation therapy (ADT), time to castration refractory prostate cancer (CRPC), cause-specific survival and in field pelvic and para-aortic disease control.

Study design: The PART-trial is a non-randomized phase II trial.

Study population: Men with histological proven adenocarcinoma of the prostate (cT1-4; pT2-4) and presence of pN1 disease after ePLND are eligible for the study. For trial-inclusion, pN1 disease is defined on the basis of one of following criteria: (1) two or more positive LN; (2) ratio positive LN / removed LN > 7%; (3) presence of extracapsular LN extension. Patients referred for external beam radiotherapy (EBRT) who fulfill the inclusion criteria and without any of the exclusion criteria will be included in the present trial after written informed consent.

Intervention: Patients included in the PART-trial receive radiotherapy to the prostate or prostate bed and the pelvic lymph nodes according to the current standard. Furthermore patients in the PART-trial receive an additional elective radiation to the para-aortic lymph nodes. The total radiation dose that will be delivered to the para-aortic lymph node area is 45 Gy in 25 fractions of 1.8 Gy. Androgen deprivation therapy is foreseen in this trial for 24 months (long term).