Rectal Cancer Watch & Wait Management: Experience of 545 Patients from the U.S. Rectal Cancer Research Group.

Background: The use of a watch and wait management strategy following a complete clinical response to neoadjuvant therapy for rectal cancer is increasing. However, insights into implementation, treatments, and outcomes, on a United States national level, are limited.

Objective: To investigate and report on watch & wait management practices and outcomes in the US.

Design: Retrospective study.

Setting: Multicenter.

Patients: Stage II or III rectal cancer patients who underwent intentional watch & wait management between January 2015 and August 2022.

Main outcome measures: Patient and tumor characteristics, neoadjuvant treatment and response, local cancer regrowth and metastasis, salvage surgery, overall and disease-specific survival.

Results: Among 545 patients from 33 centers, follow-up was 21 months (range, 9-37). Total neoadjuvant therapy or other types of neoadjuvant were used in 395 (72%) and 150 (28%) of patients, respectively. Estimated 3-year local regrowth rate was 23.8% (95% CI: 19.1-29.4%). Patients with local regrowth had higher distant metastases incidence (14.2% vs. 3.5%, p < 0.001). Salvage surgery was performed in 74/84 (88%) patients with local regrowth and included rectal resection in 66 (89%), and local excision in 8 (11%). Of 64 salvage resections with known pathology results, 58 (91%) were margin-negative. Overall, 3-year overall survival was 94.8% (95% CI: 90.5 - 97.2%) and 3-year disease specific survival 96.2% (95% Cl 91.8 - 98.2%). Patients with and without local regrowth exhibited 3-year overall survival of 83.6% (95% Cl 68.4 - 91.9%), and 97.7% (95% CI: 93.3 - 99.2%), respectively.

Limitations: Retrospective study.

Conclusion: This multicenter study indicates that the watch & wait approach for locally advanced rectal cancer is feasible with acceptable outcomes across a variety of geographical regions and practice settings in the US. Local regrowth and distant metastasis rates were within published norms and salvage surgery proved effective. See Video Abstract.