Nodal and osseous oligometastatic prostate cancer: a cohort including the introduction of PSMA-PET/CT-guided stereotactic and hypofractionated radiotherapy with elective nodal therapy

Abstract

Purpose: Oligometastatic prostate cancer is heavily investigated, and conventionally fractionated elective nodal treatment appears to increase biochemical relapse-free (bRFS) survival. The novelty of this report is to present elective nodal radiotherapy (ENRT) with simultaneous integrated boost with stereotactic (SBRT) or hypofractionated radiotherapy (HoFRT) for tolerance and for bRFS which we compared with SBRT of the involved field (IF) only. Materials and methods: Patients between 2018 and 2021 with and oligometastatic prostate cancer treated with SBRT or hypofractionation were eligible. A radiobiologically calculated simultaneous integrated boost approach enabled to encompass elective nodal radiotherapy (ENRT) with high doses to PSMA-positive nodes. A second group had only involved field (IF) nodal SBRT. Results: A total of 44 patients with 80 lesions of initially intermediate- (52%) or high-risk (48%) D’Amico omPC were treated with SBRT to all visible PSMA-PET/CT lesions and 100% of the treated lesions were locally controlled after a median follow-up was 18 months (range 3–42 months). Most lesions (56/80; 70%) were nodal and the remainder osseous. Median bPFS was 16 months and ADT-free bPFS 18 months. ENRT (31 patients) versus IF (13 patients) prevented regional relapse more successfully. At univariate analysis, both initial PSA and length of the interval between primary diagnosis and biochemical failure were significant for biochemical control. Treatment was well tolerated and only two patients had toxicity ≥ grade 3 (1 GU and 1 GI, each). Discussion/conclusion: SBRT and hypofractionated radiotherapy at curative doses with ENRT was more effective to delay ADT than IF, controlled all treated lesions and was well tolerated.