A retrospective analysis of 44 diminutive rectal neuroendocrine neoplasms that were not suitable for local treatment.

BACKGROUND

Diminutive rectal neuroendocrine neoplasms (NENs) are often treated by local excision, but the presence of regional nodes or distant metastasis is reported in an increasing number of reports.

METHODS

We retrospectively recruited 44 patients with rectal NENs below 2 cm. These patients were not suitable for local excision due to invasion of the muscularis propria, involvement of regional lymph nodes or distant metastasis. A multivariate logistic regression model was conducted to identify the risk factors for distant metastasis. Survival analysis was performed to evaluate their prognosis.

RESULTS

Among 44 patients, 11 (25 %) had NENs smaller than 1 cm, and 33 (75 %) had NENs 1-2 cm in size. Thirty-seven patients (84.1 %) had regional node metastasis, and 14 (31.8 %) presented distant metastasis. The depth of tumor invasion (odds ratio [OR] = 20.57, 95 % confidence interval [CI]: 2.17-194.95, P = 0.008) was identified as the dominant risk factor for distant metastasis. The median overall survival (OS) was 86 months in the whole cohort, and the 1-year, 3-year and 5-year OS rates were 88.5 %, 81.9 % and 73.0 %, respectively. Poor histological differentiation (hazard ratio [HR] = 11.65, 95 % CI: 2.75-49.38, P = 0.001) and metastatic disease (HR = 7.45, 95 % CI: 1.73-32.03, P = 0.007) were significantly associated with worse OS.

CONCLUSIONS

Diminutive rectal NENs are still at risk of regional and even distant metastasis. A prudent attitude should be maintained with respect to choosing local excision as size alone is not a sufficient criterion for treatment decisions.