How Does Omitting Additional Surgery After Local Excision Affect the Prognostic Outcome of Patients With High-risk T1 Colorectal Cancer?

Objective: To investigate how omitting additional surgery after local excision (LE) affects patient outcomes in high-risk T1 colorectal cancer (CRC). Summary Background Data: It is debatable whether additional surgery should be performed for all patients with high-risk T1 CRC regardless of the tolerability of invasive procedures. Methods: Patients who had received LE for T1 CRC at the Japanese Society for Cancer of the Colon and Rectum (JSCCR) institutions between 2009 and 2016 were analyzed. Those who had received additional surgical resection and who did not were matched one-on-one by the propensity score (PS)-matching method. A total of 401 PS-matched pairs were extracted from 1,975 patients at 27 JSCCR institutions and compared. Results: Regional lymph node metastasis was observed in 31 (7.7%) patients in the LE+surgery group. Comparatively, the incidence of oncologic adverse events was low in the LE-alone group, such as the 5-year cumulative risk of local recurrence (4.1%) or overall recurrence (5.5%). In addition, the difference in the 5-year CSS between the LE+surgery and LE-alone groups was only 1.8% (99.7% and 97.9%, respectively), whereas the 5-year OS was significantly lower in the LE-alone group than in the LE+surgery group (88.5% vs. 94.5%, respectively ( P =0.002). Conclusions: Those who had been decided to omit additional surgery at the dedicated center for CRC treatment presented a small number of oncologic events and a satisfactory CSS, which may suggest an important role of risk assessment regarding non-oncologic adverse events to achieve a best practice for each individual with high-risk T1 tumors.