Efficacy analysis of high-dose-rate brachytherapy combined with total neoadjuvant therapy versus total neoadjuvant therapy alone.

Abstract

e15663 Background: Colorectal cancer is the third most common tumors and the second leading cause of cancer-related deaths worldwide. Most patients are diagnosed with locally advanced rectal cancer (LARC), which is associated with high recurrence risks and low survival rates. The standard treatment for LARC is preoperative neoadjuvant chemoradiotherapy combined with total mesorectal excision (TME). However, only a small proportion of patients achieve pathological complete response (pCR) after treatment, and approximately 30% develop distant metastases following neoadjuvant therapy. How to strengthen or optimize the preoperative neoadjuvant therapy of LARC to benefit more patients is a critical focus of current clinical research. High-dose-rate brachytherapy (HDR-BT) offers the potential to deliver higher radiation doses to tumors while sparing surrounding tissues and organs from radiation damage. Limited studies have investigated the combination of total neoadjuvant therapy (TNT) with HDR-BT. This retrospective study aims to compare the efficacy and safety of TNT combined with HDR-BT versus TNT alone, with the goal of providing new insights into comprehensive treatment strategies for LARC patients. Methods: Patients with LARC who received neoadjuvant therapy in our hospital from May 2016 to July 2024 were retrospectively screened according to inclusion and exclusion criteria. Clinical information, neoadjuvant treatment regimens, and serological indexes were collected. Pathological staging, tumor regression grade, R0 resection status, overall survival (OS), disease-free survival (DFS), Recurrence-free survival (RFS), and incidence of adverse reactions were recorded. The efficacy and safety of the two groups were compared. Results: This study included a total of 86 patients, with 50 in the TNT group and 36 in the TNT+HDR-BT group. There was no statistical significance in the distribution of clinical characteristics, concurrent and consolidation chemotherapy regimens between the two groups. In the TNT+HDR-BT group, 11 patients (31.4%) achieved pathological complete response (pCR), which was numerically higher than 10.0% in the TNT group (P = 0.013). The median follow-up time in the TNT+HDR-BT group and the TNT group was 68.7 months and 56.7 months, respectively. 5 year DFS was 72.2% in the TNT+HDR-BT group and 59.8% in the TNT group (HR = 0.66, 95% CI 0.31-1.43, P = 0.292). 5 year RFS was 82.5% in the TNT+HDR-BT group and 67.2% in the TNT group (HR = 0.45, 95% CI 0.17-1.16, P = 0.091). 5 year OS was 87.9% in the TNT+HDR-BT group and 70.3% in the TNT group (HR = 0.34, 95% CI 0.11-1.04, P = 0.046). Conclusions: Compared with TNT, TNT combined with HDR-BT in the treatment of LARC patients significantly increased the proportion of pCR and showed a trend of better survival outcomes.