Efficacy and safety of stereotactic ablative brachytherapy (SABT) as salvage treatment for sacral region local recurrent rectal cancer: a multicenter retrospective study

Abstract Background: To investigate the efficacy and safety of stereotactic ablative brachytherapy (SABT) as salvage treatment for sacral region local recurrent rectal cancer (S-LCCR). Materials and Methods: Fifty-two patients with S-LCCR after radical resection from January 2016 to December 2020 in four institutes were enrolled in this retrospective study. All patients received 3D-template (3D-PT) assisted SABT. Median tumor volume was 43.2 (range 3.1-178.7) cc. Local control (LC), overall survival (OS), pain relief, and adverse events was recorded and analyzed. Results: Median follow-up was 29.3 (range 15.7-42.9) months. Median LC was 24.0 (range 13.5-34.5) months. LC at 1-, 2- and 3-year were 66.7%, 46.9% and 39.1%, respectively. Median OS was 17.7 (range 9.6-25.9) months. OS at 1-, 2- and 3-year were 61.1%, 35.3% and 29.5%, respectively. Univariate analysis suggested that D90＞130Gy (P=0.007) and tumor volume ≤45cc (P=0.007) were positive prognostic factors influencing LC. Pain relief rate was 96.6% (28/29). Rate of adverse events (≥grade 3) was 7.7%. Conclusion: SABT may be a feasible and promising salvage treatment for sacral region recurrent rectal cancer after surgery.