Poorer prognosis for neuroendocrine carcinoma than signet ring cell cancer of the colon and rectum (CRC-NEC): a propensity score matching analysis of patients from the Surveillance, Epidemiology, and End Results (SEER) database.

Purpose: Colorectal neuroendocrine carcinomas (CRC-NECs) are rare, comprising < 1% of colorectal cancers. This study aimed to assess the incidence, clinicopathologic characteristics, prognostic factors, and treatment outcomes of CRC-NEC.

Methods: We analysed the Surveillance, Epidemiology, and End Results (SEER) database to identify patients from 20 to 74 years old diagnosed with CRC-NEC or common CRC (non-NEC) during 2004-2013. Log-rank testing was conducted to assess survival differences. A competing-risks regression model was used to adjust for covariate effects in the propensity score-matched (PSM) cohort, and adjusted hazard ratios (HRs) were calculated for the raw and PSM cohorts.

Results: We identified 67,484 patients (344 CRC-NEC and 67,140 non-NEC). Lymph node metastasis (LNM) was more common in CRC-NEC (75.29%, n = 259) than in non-NEC (51.53%, n = 34,600) (P < 0.001); 56.40% (n = 194) of CRC-NECs were located on the right side, while 18.31% (n = 63) were located on the left side, with a statistically significant difference in distribution (P < 0.001) compared to that in non-NEC CRC. Multivariate analysis indicated that a left-side location was an independent adverse prognostic factor for CRC-NEC (P = 0.043). CRC-NEC had the poorest cancer-specific survival (median CSS, 9.0 months) among assessed cancers, even poorer than that of signet ring cell cancer (median CSS, 24.0 months). However, both radical operation (P = 0.007) and chemotherapy (P = 0.008) were beneficial for CSS.

Conclusion: NEC is a rare and extremely aggressive tumour with a poor prognosis. Right-side NEC has a better prognosis than left-side NEC. Early diagnosis, radical surgery, and chemotherapy are imperative for improving survival.