Long term outcome of patients with rectal cancer with complete clinical response or near complete clinical response after neoadjuvant therapy: A multicenter registry study by Chinese Watch and Wait Database.

Abstract

e15597 Background: To report the long-term outcomes of Chinese rectal cancer patients after Watch and Wait (W&W) following neoadjuvant therapy(NAT). Methods: Collecting real-world multicenter retrospective data, including the Chinese W&W Database group (CWWD) and data from centers that initiated this work earlier in China. Patients with a follow-up time of no less than 2 years were included. Analyzing and reporting on their oncological outcomes and comparing differences between cCR and near-cCR groups. Results: The study included 318 rectal cancer patients from 8 institutions who received NAT and underwent W&W. Among them, 291 initially achieved cCR, and 27 had near-cCR. The median follow-up time was 48.4 months (10.2-110.3 months). The 5-year OS and CSS were 92.4% (95% CI 86.8-95.7%) and 96.6% (95% CI 92.2-98.5%), respectively. The 5-year OP-DFS(organ preservation adapted DFS) was 86.6% (95% CI 81.0-90.7%), and the 5-year OPR was 85.3% (95% CI 80.3-89.1%). The overall 5-year local regrowth rate and distant metastasis rate were 18.5% (95% CI 14.9-20.8%) and 8.2% (95% CI 5.4-12.5%), respectively. The 5-year local regrowth rate in the near-cCR group was higher than in the cCR group (41.6% vs. 16.4%, p<0.01), with a lower OPR rate (69.2 vs. 88.0%, p<0.001). However, there were no significant differences in OS, CSS, and OP-DFS between the two groups. 91% of local regrowths occurred within the intestinal lumen, 7.2% (4/56) occurred simultaneously in the intestinal lumen and mesentery, and 1.8% (1/56) occurred only in the mesentery. 82.1% of local regrowths occurred within 2 years, 91.0% occurred within 3 years, with a median regrowth time of 11.7 months (2.5-66.6 months). Among cases with local regrowth beyond 2 years, 30% (3/10) had mesenteric regrowth. The salvage success rate after local regrowth (conversion to disease-free status after salvage surgery) was 82.1% (46/56). 60.8% of distant metastases occurred within 2 years, 73.9% occurred within 3 years. Common sites included lung metastasis (65.2%), liver metastasis (34.8%), and bone metastasis (30.4%), with 26% involving multiple organs. 83.3% (5/6) of liver metastases occurred within 2 years, while lung and bone metastases spread out over 5 years follow-up. Among patients with local regrowth, 16.0% (9/56) developed distant metastases. The salvage success rates for local regrowth and distant metastasis were 82.1% (46/56) and 12.5% (3/23), respectively. Conclusions: Rectal cancer patients who achieve cCR or near-cCR after NAT and undergo W&W have favorable oncological outcomes and a high rate of organ preservation. Local regrowth and distant metastasis during W&W follow certain patterns, with a relatively high salvage rate for local regrowth. It emphasizes the importance of close follow-up and timely intervention during the W&W process.