Transanal endoscopic microsurgery for T1 rectal cancer: size matters!

Transanal endoscopic microsurgery (TEM) is considered a curative option for selected T1 rectal cancer. Although TEM is safe, local recurrence (LR) rates after TEM are unacceptably high. Evidence on selection criteria, however, is not abundant. To expand evidence on low- versus high-risk T1 rectal cancer with respect to LR, this study aimed to identify predictive histopathologic factors in a selected group of T1 rectal cancers treated with TEM only. The study enrolled 62 patients for whom specimens of the primary tumor containing an invasive T1 carcinoma could be reevaluated. Tumors were scored according to predefined criteria, and analysis of predictive factors for locoregional failure was performed. Local recurrence rates at 3 years for tumors 3 cm in size or smaller were significantly lower than for tumors larger than 3 cm (16 vs. 39%; P < 0.03). Combining smaller tumors with submucosal invasion depth and budding led to identifying tumors that likely will not recur (3-year LR rates, 7 and 10%, respectively). The findings showed that low- and high-risk criteria are too robust for identifying tumors at risk for LR. Tumor size alone or in combination with submucosal invasion depth or tumor budding appeared to be a significant predictive factor for locoregional failure after TEM for T1 rectal cancer.