3234 - Salvage HDR Brachytherapy for Locally Recurrent Prostate Cancer after Radiotherapy: Long-Term Outcomes and Predictive Factors
Presenter(s)
W. Burchardt1,2, A. Kluska1, A. Chyrek1,2, and A. Chichel1; 1Greater Poland Cancer Centre, Poznan, Brachytherapy Department, Poznan, Poland, 2Poznan University of Medical Sciences, Electroradiology Department, Poznan, Poland
Purpose/Objective(s): Management of locally recurrent prostate cancer (rPC) after definitive radiotherapy remains challenging. While salvage radical prostatectomy is potentially curative, it is associated with substantial morbidity. Salvage brachytherapy (sBT) represents an alternative approach, yet long-term oncologic outcomes and predictors of response remain incompletely defined. We retrospectivly evaluated toxicity, clinical outcomes, and prognostic factors in patients treated with sBT for rPC.
Materials/Methods: Seventy patients (median age 70.2 years) with biopsy- or imaging-confirmed local recurrence after prior radiotherapy were treated with salvage brachytherapy between 2010 and 2021. Primary treatment included EBRT (n=16), EBRT+BT boost (n=23), HDR brachytherapy (n=12), LDR brachytherapy (n=17), or SBRT (n=3). Median time to biochemical recurrence after primary therapy was 65.7 months. Salvage HDR brachytherapy was delivered as 3×10 Gy (n=44), 2×13 Gy (n=25), or 1×19 Gy (n=2).
Results: Median follow-up was 67.5 months. Acute grade 3 genitourinary (GU) toxicity occurred in 14.3% of patients; no grade 4 events were observed. Acute gastrointestinal (GI) toxicity was minimal (grade 0–1 in 100%). Late GU toxicity remained predominantly = grade 2 in over 85% of patients. Late GI toxicity was rare (95.7% grade 0). IPSS increased from a median of 6 pre-salvage to 12 post-treatment (p<0.001) but remained stable during follow-up. Five-year BFFS was 39%, while 5-year LC and DMFS were 69% and 71%, respectively. No difference in BFFS was observed between HDR dose schedules (3× 10 Gy vs 2×13 Gy; p=0.33). Androgen deprivation therapy did not significantly impact BFFS, LC, or DMFS. On multivariable analysis, higher ISUP grade at recurrence (HR 1.49, p=0.008), higher PSA at recurrence (HR 1.28, p=0.035), shorter PSA doubling time (HR 0.93 per month, p=0.045), and worse performance status (PS) (HR 4.37, p=0.02) independently predicted biochemical failure. ROC analysis identified PSA doubling time (PSADT) >9.2 months and PSA <4 ng/mL at recurrence as optimal cut-offs associated with improved BFFS (p=0.001).
Conclusion: Salvage brachytherapy provides durable local control with very good long-term toxicity in appropriate selected patients with radiorecurrent prostate cancer. HDR dose schedules have equal efficacy in treatment of rPC. Biochemical outcomes remain below the average , however the median follow up is one of the longest in the literature. Moreover the patients were mainly from pre PET PSMA era. The PSADT and PSA level at recurrence, ISUP grade , PS strongly predict treatment success.