ESTRO 2020 Abstract Book

S633 ESTRO 2020

Conclusion MMT for M1a PC is feasible, with grade 3 and 4 toxicity occurring in a minority of patients. Although follow-up is short, first results on cancer-specific survival are promising. PO-1201 Oligorecurrent prostate cancer treated with metastasis-directed therapy: oncological outcomes G. Devos 1 , C. Berghen 2 , S. Joniau 1 , K. Poels 2 , K. Haustermans 2 , K. Rans 2 , G. De Meerleer 2 1 University Hospital Gasthuisberg, Urology, Leuven, Belgium ; 2 University Hospital Gasthuisberg, Radiation Oncology, Leuven, Belgium Purpose or Objective To evaluate the oncological results of treatment with metastasis-directed therapy (MDT) for patients presenting with oligorecurrent hormone-sensitive prostate cancer (HSPC). Material and Methods We retrospectively analysed the outcome of patients treated with MDT for oligorecurrent HSPC, defined as the recurrence of 1-5 pelvic nodal (N1) and/or metastatic lesions (M1a-c) following maximal treatment of the primary tumor. Between 01/2005 and 01/2019, 215 patients with 406 lesions were included in this analysis. Results Of the 215 patients, 87 patients (151 lesions) were treated with radiotherapy, of which 55 (82 lesions) were treated with stereotactic body radiation therapy (SBRT). 117 patients were treated with lymphadenectomy (LAD) for cN1 or cM1a disease OR metastasectomy for M1b/c disease (n=11). In case of pN1 disease after LAD, postoperative pelvic/retroperitoneal radiotherapy was administered together with 24 months of androgen-deprivation therapy (ADT). In case of SBRT to a metastatic lesion, 1 month of ADT was given as radiosensitizer. In total, 115 patients (53%) received ADT. After a median follow-up of 35 months (IQR 19-61 months), the median clinical relapse-free survival was 27 months (95% CI 23-32). The ADT-free survival was 65 months (95% CI 49-83). The median ADT-free survival for patients with only N1 disease was significantly longer than patients with the M1a-c disease: not reached vs. 65 months (95% CI 49- 83, p=0.02). The median castration-refractory prostate cancer (CRPC)-free survival and median cancer-specific survival (CSS) were not reached, with only 34 and 8 events respectively, resulting in crude CRPC-free survival of 80% at 5 years. Crude CSS was 95% at 5 years.

Conclusion In this large cohort, treatment with MDT for oligorecurrent HSPC provides excellent oncologic outcomes and has great potential to postpone disease progression and the use of ADT and its side effects. PO-1202 CHHiPvsPROFIT for Localized Prostate Cancer:A Retrospective Dosimetric Comparison of Organs at Risk. P. Ramia 1 , A. Mkanna 1 , B. Shahine 1 , Z. Makke 2 , L. Hilal 1 , F. Geara 1 , M. Adel 1 , F. Olleik 1 , B. Youssef 1 1 American University of Beirut, Radiation Oncology, Beirut, Lebanon ; 2 Lebanese University, Physics, Beirut, Lebanon

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