Nonoperative Management of Rectal Cancer: Is "Near-Complete" Response Safe to Surveil?

Background: Nonoperative management of rectal cancer in patients who achieve near-complete response following total neoadjuvant therapy remains controversial and understudied.

Methods: This retrospective cohort study conducted at a tertiary National Cancer Institute-designated cancer center included patients with rectal cancer who initiated active surveillance after achieving near-complete response following induction radiotherapy and consolidation chemotherapy. Near-complete response was determined based on restaging endoluminal evaluation and pelvic magnetic resonance imaging. Time-to-event analyses were used to estimate regrowth-free, proctectomy-free, disease-free, and overall survival.

Results: Of 61 patients who achieved near-complete response and initiated nonoperative management between February 2017 and March 2024, 36 (59.0%) maintained organ preservation with a median follow-up of 27.1 (interquartile range [IQR] 17.4-37.4) months. Twenty-five patients (41.0%) developed local regrowth by a median of 5.7 (IQR 3.2-8.2) months. All regrowths occurred within 17.5 months of initial restaging. Twenty-one patients with regrowth underwent salvage proctectomy, of which 20 (95.2%) achieved R0 resection margins. Following salvage proctectomy, four patients (19.0%) developed local recurrence. Disease-free and overall survival 2 years from restaging were 79.2% (95% confidence interval [CI] 67.0-93.6) and 93.3% (95% CI 86.3-100), respectively. Overall survival was not significantly different between patients with versus without local regrowth (log-rank p = 0.09).

Conclusions: Nonoperative management achieves clinically significant organ preservation rates without compromising oncologic outcomes in patients with near-complete response to total neoadjuvant therapy. Active surveillance allows time for continued evolution of tumor response and may substantially expand organ preservation in a patient population who otherwise would undergo avoidable radical surgery.