RESUMO
Background and study aims A free resection margin (FRM)â>â1âmm after local excision of a T1 colorectal cancer (CRC) is known to be associated with a low risk of local intramural residual cancer (LIRC). The risk is unclear, however, for FRMs between 0.1 to 1âmm. This study evaluated the risk of LIRC after local excision of T1 CRC with FRMs between 0.1 and 1âmm in the absence of lymphovascular invasion (LVI), poor differentiation and high-grade tumor budding (Bd2-3). Patients and methods Data from all consecutive patients with local excision of T1 CRC between 2014 and 2017 were collected from 11 hospitals. Patients with a FRM ≥â0.1âmm without LVI and poor differentiation were included. The main outcome was risk of LIRC (composite of residual cancer in the local excision scar in adjuvant resection specimens or local recurrence during follow-up). Tumor budding was also assessed for cases with a FRM between 0.1 and 1mm. Results A total of 171 patients with a FRM between 0.1 and 1âmm and 351 patients with a FRMâ>â1âmm were included. LIRC occurred in five patients (2.9â%; 95â% confidence interval [CI] 1.0-6.7â%) and two patients (0.6â%; 95â% CI 0.1-2.1â%), respectively. Assessment of tumor budding showed Bd2-3 in 80â% of cases with LIRC and in 16â% of control cases. Accordingly, in patients with a FRM between 0.1 and 1âmm without Bd2-3, LIRC was detected in one patient (0.8%; 95â% CI 0.1-4.4â%). Conclusions In this study, risks of LIRC were comparable for FRMs between 0.1 and 1âmm and >â1âmm in the absence of other histological risk factors.