Background The treatment strategies for T1 colorectal cancer (CRC) remain controversial. We aimed to investigate the long-term outcomes of the different treatments and evaluate the risk factors for the prognosis.

Methods We enrolled patients with T1 CRC between February 2010 and August 2021. The patients were divided into 4 groups based on their treatment: Group A, endoscopic resection; Group B, endoscopic or transanal local resection with additional radical resection; Group C, transanal local resection; Group D, radical resection. Their medical histories were retrospectively reviewed, and follow-up results were obtained by medical histories or telephone calls.

Results 1034 patients were finally chosen for analysis, whose mean age was 58.6±11.7 years old. The number of patients was 121, 200, 99, and 614 in each group, respectively. With a median follow-up of 49 months, 56 patients had recurrence (5.42%). The 5-year recurrence-free (RFS) survival rates in each group were 92.2%, 98.0%, 79.8%, and 93.2% (P<0.001), respectively. The 5-year overall survival (OS) rates in each group were 88.8%, 94.7%, 84.9%, and 95.1%, respectively (P=0.051). The differences in RFS and OS mainly lay in the patients with risk factors based on Japanese Society for Cancer of the Colon and Rectum (JSCCR) guidelines. Multivariate analyses identified tumor size≥ 2 cm (HR 1.911; 95% CI 1.019–3.583), rectal cancer (HR 2.129; 95% CI 1.158–3.915), lymphovascular invasion (HR 2.954; 95% CI 1.328–6.573), and tumor histologic grade (HR 3.199; 95% CI 1.565–6.538) as independent predictive factors of RFS, and rectal cancer (HR 2.107; 95% CI 1.165–3.810), lymphovascular invasion (HR 3.041; 95% CI 1.290–7.166), and age group (HR 5.185; 95% CI 1.619–16.610) as an independent predictive factor of OS.

Conclusions The long-term outcomes of local resection are comparable to those of surgery in patients without high-risk factors, while for those with high-risk factors transanal local resection showed poorer RFS and OS when compared with other groups. Tumor size≥ 2 cm, rectal cancer, lymphovascular invasion, tumor histologic grade, and age group may be important long-term prognostic factors for T1 CRC patients.