Incidence and survival of adenocarcinoma with mixed subtypes in patients with colorectal cancer.

Background: Limited attention was paid to adenocarcinoma with mixed subtypes (AM) of the colon and rectum due to its low incidence. This study aims to assess the frequency and survival rates of tumors in the population.

Methods: The data were extracted from the Surveillance, Epidemiology, and End Results (SEER) database between 2000 and 2019. The incidence of tumors was evaluated based on patient gender, age, race, and location. Univariate and multivariate Cox analyses were performed to identify risk factors associated with tumor survival. Additionally, a nomogram was constructed using these risk factors to predict cancer-specific survival (CSS) at 1, 2, and 3 years. Receiver operating characteristic (ROC) and calibration curves were applied to examine the model's accuracy.

Results: The overall incidence of colorectal AM reached its highest level in 2016 (2.350 (95% CI: 2.241-2.462)). AM is more frequent in elderly patients and predominantly located in the rectum. By forest plot for multivariable Cox regression analysis, patient age, the number of regional positive lymph nodes and lymph nodes removed, tumor N/M stage, and postoperative chemotherapy were identified as independent risk indicators for CSS. Nomogram was constructed and validated as a feasible prediction model of CSS in patients with colorectal AM.

Conclusion: The presence of colorectal AM in elderly patients, particularly in the rectum, is frequent and often associated with poor prognosis. Our nomograms can offer a relatively accurate prediction of CSS of patients with AM after tumor resection.