Which prognostic factors for recurrence after transanal endoscopic microsurgery for early rectal cancer?

[BACKGROUND] Transanal endoscopic microsurgery (TEM) enables the local excision of rectal neoplasms with minimal invasiveness; however, the long-term oncologic safety for pTis and pT1 lesions, as well as the significance of traditional histopathological risk factors, remains controversial.

[METHODS] A retrospective cohort of 170 consecutive patients undergoing en bloc, R0 full-thickness TEM for rectal pTis or pT1 adenocarcinoma between 1994 and 2025 at a single tertiary centre was analysed. Pathological review included Vienna classification, submucosal invasion (sm1 vs sm2-3), tumour grade (G1-2 vs G3), lymphovascular invasion (LVI), mucinous histotype, tumour budding, perineural invasion (PNI), and tumour diameter (> 3 cm). Patients with adverse features were recommended salvage radical surgery or adjuvant radiotherapy. Disease-free (DFS) and overall survival (OS) were estimated using Kaplan-Meier analysis and log-binomial regression.

[RESULTS] The median age was 71 years (IQR, 62-77), and the median follow-up was 24 months (IQR, 24-53). Lesion distribution was Vienna 4.2 (n = 21), Vienna 4.4 (n = 21), pT1sm1 (n = 48), pT1sm2 (n = 40), and pT1sm3 (n = 40). All patients achieved R0 excision. No recurrences were observed in the Vienna 4.2/4.4 groups. For pT1 tumours, recurrence rates were 4.2% (sm1), 37.5% (sm2), and 20.0% (sm3). On multivariate analysis, submucosal invasion (sm2-3; HR 5.67, p = 0.021), high grade (G3; HR 3.58, p = 0.004), and LVI (HR 3.58, p = 0.003) were independent predictors of DFS. Other factors were not significant. In OS analysis, older age (> = 71 years) and tumour diameter > 3 cm were associated with poorer survival, whereas classical high-risk pathological factors (sm2-3, G3, LVI) were not.

[CONCLUSION] TEM affords excellent long-term disease control for Vienna 4.2/4.4 lesions. In pT1 adenocarcinoma, only submucosal invasion beyond sm1, high grade, and LVI independently predict recurrence, underscoring the need for risk-adapted, multidisciplinary management.