Main Session
Sep 28
SS 02 - GI 1: The OPERATIC Side of Rectal Cancer - Organ Preservation, Evaluating Recurrences, and the Immune Checkpoints

109 - Comparison of Patterns of Locoregional Recurrence in Total Neoadjuvant Therapy vs. Chemoradiotherapy for Locally Advanced Rectal Cancer in the STELLAR Study

02:50pm - 03:00pm PT
Room 307/308

Presenter(s)

Jiacheng Shuai, MD Headshot
Jiacheng Shuai, MD - Peking Union Medical College Hospital, Beijing, Beijing

J. Shuai1, T. Xu1, H. Li1, H. Ma1, N. Wang1, H. Zhou2, N. Li1,3, H. Zhang2, Y. LI1, Y. Tang4, and J. Jin1,5; 1State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing, China, 2State Key Laboratory of Molecular Oncology and Department of Colorectal Surgery, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College (PUMC), Beijing, China, 3Department of Radiobiology, Shanxi Province Cancer Hospital/ Shanxi Hospital Affiliated to Cancer Hospital, Chinese Academy of Medical Sciences/Cancer Hospital Affiliated to Shanxi Medical University, Taiyuan, China, 4Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing, China, 5Department of Radiation Oncology, National Cancer Center / National Clinical Research Center for Cancer / Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen, China

Purpose/Objective(s):

The patterns of locoregional recurrence (LR) following total neoadjuvant therapy (TNT) in patients with locally advanced rectal cancer (LARC) have been rarely reported. This study evaluated results of locoregional control and patterns of LR between TNT and chemoradiotherapy (CRT), based on the surgical subset of STELLAR study population.

Materials/Methods:

Patients with LARC from the STELLAR study were randomized to either TNT (25 Gy/5F + 4*CAPOX) or CRT (50 Gy/25F + concurrent capecitabine), and those who underwent surgery following preoperative treatment were analyzed for patterns of LR. LRs were classified into five regions: (1) anastomotic or mesorectal, (2) presacral, (3) anterior, (4) lateral, and (5) perineal. Comprehensive analyses included timing, post-recurrence survival, clinicopathological risk factors, and distribution of LR.

Results:

The analysis was conducted on 465 patients undergoing surgery (TNT: 235; CRT: 230) with T3-4 disease (97.7%), node-positive status (86.0%), mesorectal fascia involvement (55.7%), and extramural vascular invasion (52.9%). The median follow-up was 69.7 months (IQR: 50.4 – 82.4). 5-year cumulative LR rates were 8.7% (21/235) in the TNT group and 9.1% (24/230) in the CRT group (P = 0.86). LR occurred within 2 years (52% vs 54%, P=0.87) and 3 years (86% vs 83%, P=0.83) in the TNT and CRT groups, respectively. Distant metastases accompanied 40% of LRs (TNT:7, CRT:11). Median survival after LR showed no statistical difference between TNT and CRT groups (71.5 months vs 34.0 months, P = 0.065). In a multivariate Cox regression analysis, ypN status (P = 0.008) was significantly associated with LR. Spatial distribution analysis was conducted on 390 patients who had surgery across 11 of the 15 centers, with combined recurrence rates across anatomical sites as follows: presacral (12/34, 35.3%), anastomotic/mesorectal (11/34, 32.4%), perineal (9/34, 26.5%), lateral (4/34, 11.8%), anterior (3/34, 8.8%), and unknown (11/34, 32.4%). Treatment-stratified recurrence distributions: TNT (n=16): presacral (10/16, 62.5%), anastomotic/mesorectal (6/16, 37.5%), perineal (5/16, 31.3%), anterior (2/16, 12.5%), lateral (2/16, 12.5%), and unknown (2/16, 12.5%); CRT (n=18): anastomotic/mesorectal (5/18, 27.8%), perineal (4/18, 22.2%), presacral (2/18, 11.1%), lateral (2/18, 22.2%), anterior (1/18, 5.6%), and unknown(9/18, 50.0%). Notably, there was a significant difference in presacral recurrence between the two groups (62.5% vs. 11.1%, P = 0.036).

Conclusion:

In patients with LARC, both TNT and CRT achieved low LR rates. TNT with short-course radiotherapy demonstrated similar locoregional control, temporal patterns of LR, and post-recurrence survival to CRT. However, spatial distributions of LR differed between groups, with presacral recurrence being the most common LR type in the TNT group.