Abstract

Giulio Francolini¹, Chiara Bellini², Vanessa Di Cataldo³, Beatrice Detti¹, Alessio Bruni⁴, Giulia Alicino⁵, Luca Triggiani⁶, Salvatore La Mattina⁶, Rolando Maria D'Angelillo⁷, Chiara Demofonti⁷, Rosario Mazzola⁸, Francesco Cuccia⁸, Filippo Alongi⁸, Michele Aquilano², Andrea Gaetano Allegra², Lucia Pia Ciccone², Giulia Stocchi², Viola Salvestrini², Barbara Guerrieri², Lorenzo Livi²

¹Azienda Ospedaliera Universitaria Careggi, Radiotherapy Unit, Florence, Italy; ²University of Florence, Department of Experimental and Clinical Biomedical Sciences "M. Serio", Florence, Italy; ³Istituto Fiorentino di Cura e Assistenza (IFCA), Radiotherapy Unit, Florence, Italy; ⁴Modena Hospital, Radiation Oncology Unit, Modena, Italy; ⁵Radiation Oncology Unit, Modena Hospital, Modena, Italy; ⁶University and Spedali Civili Hospital, Department of Radiation Oncology, Brescia, Italy; ⁷Policlinico Tor Vergata University, Department of Radiation Oncology, Rome, Italy; ⁸IRCCS, Sacro Cuore Don Calabria Hospital, Negrar, Radiation Oncology Department, Verona, Italy

Salvage radiotherapy is the main treatment option for biochemical relapse (BCR) after radical prostatectomy (RP). However, novel imaging methods allowed to increase staging sensibility in BCR setting, with Choline and PSMA PET showing a detection rate of 86-93% and 33-99%, respectively, depending on PSA values. Currently, when nodal pelvic oligorecurrent disease is detected, no standard treatment option is recommended, and comparative data between different management strategies are lacking. One possible salvage option is nodal stereotactic body radiotherapy (SBRT). However, one of the main criticism of nodal SBRT alone may be avoidance of prophilactic irradiation of prostate bed and elective nodal volumes. For this reason, we analysed recurrence patterns after nodal SBRT in patients affected by pelvic oligometastatic relapse after RP, and androgen deprivation therapy (ADT) free survival in this population.

Data about 68 patients consecutively treated in 5 different institutions for pelvic oligorecurrent disease were retrospectively reviewed and collected. Inclusion criteria were BCR after RP and imaging showing < 3 metachronous lymphoadenopaties under aortic bifurcation. Patients underwent SBRT on all sites of disease. Concomitant ADT was allowed. Patients treated on prostate bed +/- pelvic nodal volumes were excluded from the analysis.

After a median follow-up of 23 months (IQR 14-47), 43 patients had post-SBRT radiological evidence of relapse, for a median disease-free survival (DFS) of 18 months (95% CI 9-29). Concomitant ADT was administered in 13 (19.1%) patients. Considering only patients in whom concomitant ADT was not administered, median ADT-free survival was not reached. Overall, 8 (11.8%), 18 (26.4%) and 17 (25%) patients had prostate bed only, pelvic nodal or distant relapse, respectively. Concomitant ADT, ISUP pattern at diagnosis < or > 3, time to relapse < or > 12 months, PSA at recurrence < or > 1.10 ng/m and PSMA staging were not significantly associated with DFS. After relapse, 30 patients (44.1%) received a second SBRT course +/- ADT, 5 patients (7.3%) received prostate bed radiotherapy +/-ADT, 6 patients (8.8%) received ADT alone and 2 patients (2.9%) received ADT+anti androgen therapy.

Nodal SBRT yielded encouraging DFS and ADT-free survival in this population. Despite the high rate of recurrences, only a minority of patients developed prostate bed recurrence, suggesting that local treatment may be safely avoided. Considering the high percentage of patients managed with a second SBRT course or developing distant metastases, upfront pelvic prophilactic treatment could be considered unnecessary in this population. In order to maximize benefit of this approach in pelvic nodal relapse setting, reliable selection criteria are needed. Interestingly, early detection of nodal relapse with PSMA staging did not seem to influence outcome in this setting.