Therapeutic strategies for ypT1 rectal cancer after neoadjuvant chemoradiotherapy: a retrospective cohort study.

Purpose: The optimal treatment of ypT1 rectal cancer after neoadjuvant chemoradiotherapy (nCRT) remains controversial. This study aimed to determine whether local excision is non-inferior to radical surgery and whether adjuvant chemotherapy (ACT) would improve survival in patients with ypT1 rectal cancer after nCRT.

Methods: We enrolled 1212 and 91 patients with ypT1 rectal cancer underwent nCRT followed by radical surgery from the SEER database (2004-2018) and the Zhejiang Cancer Hospital (ZJCH) (2010-2022), respectively. Another 62 patients underwent LE were also identified from SEER registries. Propensity score matching was performed to balance baseline characteristics between patients in different treatment groups.

Results: Regional nodal metastasis was histopathologically detected in 257 patients (20.7%) within the SEER cohort, showing a significant association with poor cancer-specific survival (CSS) and overall survival (OS). Consistent findings were also observed in the ZJCH cohort. After 1:1 propensity score matching (60 pairs), no significant differences were observed between the extended resection and local excision groups in CSS (hazard ratio [HR] 0.88, P = 0.785) and OS (HR 0.81, P = 0.450). Patients with regional nodal metastases were more likely to receive ACT, while no apparent survival benefit was observed with additional ACT after PSM adjusting (187 pairs). Notwithstanding, for individuals younger than 50 years, ACT might provide a survival benefit in CSS (HR 0.25, P = 0.033) and OS (HR 0.30, P = 0.022).

Conclusion: Although patients with ypT1 rectal cancer have a non-negligible risk for nodal metastasis, oncologic outcomes of local excision following nCRT seem to be comparable to radical surgery. ACT could not effectively improve prognosis in patients with ypT1 tumors, except for those younger than 50 years of age.