Short- and long-term outcomes in ypT2 rectal cancer patients after neoadjuvant therapy and local excision: a multicentre observational study.

Background: Although local excision (LE) after neoadjuvant treatment (NT) has achieved encouraging oncological outcomes in selected patients, radical surgery still remains the rule when unfavorable pathology occurs. However, there is a risk of undertreating patients not eligible for radical surgery. The aim of this study was to evaluate the outcomes of patients with pathological incomplete response (ypT2) in a multicentre cohort of patients undergoing LE after NT and to compare them with ypT0-is-1 rectal cancers.

Methods: From 2010 to 2019, all patients who underwent LE after NT for rectal cancer were identified from five institutional retrospective databases. After excluding 12 patients with ypT3 tumors, patients with ypT2 tumors were compared to patients with ypT0-is-1 tumors). The endpoints of the study were early postoperative and long-term oncological outcomes.

Results: A total of 177 patients (132 males, 45 females, median age 70 [IQR 16] years) underwent LE following NT. There were 46 ypT2 patients (39 males, 7 females, median age 72 [IQR 18.25] years) and 119 ypT0-is-1 patients (83 males, 36 females, median age 69 [IQR 15] years). Patients with pathological incomplete response (ypT2) were frailer than the ypT0-is-1 patients (mean Charlson Comorbidity Index 6.15 ± 2.43 vs. 5.29 ± 1.99; p = 0.02) and there was a significant difference in the type of NT used for the two groups (long- course radiotherapy: 100 (84%) vs. 23 (63%), p = 0.006; short-course radiotherapy: 19 (16%) vs. 17 (37%), p = 0.006). The postoperative rectal bleeding rate (13% vs. 1.7%; p = 0.008), readmission rate (10.9% vs. 0.8%; p = 0.008) and R1 resection rate (8.7% vs. 0; p = 0.008) was significantly higher in the ypT2 group. Recurrence rates were comparable between groups (5% vs. 13%; p = 0.15). Five-year overall survival was 91.3% and 94.9% in the ypT2 and ypT0-is-1 groups, respectively (p = 0.39), while 5-year cancer specific survival was 93.4% in the ypT2 group and 94.9% in the ypT0-is-1 group (p = 0.70). No difference was found in terms of 5-year local recurrence free-survival (p = 0.18) and 5-year distant recurrence free-survival (p = 0.37).

Conclusions: Patients with ypT2 tumors after NT and LE have a higher risk of late-onset rectal bleeding and positive resection margins than patients with complete or near complete response. However, long-term recurrence rates and survival seem comparable.