A Comparison of Treatments and Outcomes for Medullary versus Nonmedullary Colon Cancer: A Single Institutional Experience Showing a Worse Prognosis for Stage 3 Disease.

Background: Prior studies have shown a better prognosis with medullary colon cancer (MCC) compared to nonmedullary colon carcinomas (NMC); however, data are inconsistent and lacking the evaluation of treatments received. As we did not see similar survival outcomes, we aimed to retrospectively examine survival and receipt of treatment differences between MCC and NMC within the Geisinger Health System.

Methods: The Cancer Registry was retrospectively reviewed for MCC and NMC from 2006 to 2017. Demographics and treatments were compared using T-test and chi-squared analyses, also comparing MCC to poorly differentiated (PD) or undifferentiated (UD) NMC. Overall survival was analyzed using Kaplan-Meier curves and log-rank tests.

Results: 33 MCC and 1775 NMC patients were identified and 31 (93.9%) MCC and 1433 (87.0%) NMC underwent resection. MCC were older (p=0.0002), had a higher Charlson Comorbidity Index (p=0.013) and were more likely right sided (p=0.013). Seven patients (22.6%) with MCC vs. 149 (10.4%) NMC underwent resection of contiguous organs. Overall median survival was significantly worse for MCC as compared to NMC (19.6 vs. 60.5 months, p=0.0002). Only stage 3 patients had a significantly worse median survival when compared to PD/UD NMC (9.6 vs. 47.2 months, p < 0.001). Contiguous organ resection and failure to receive chemotherapy were not found as contributing factors to decreased survival.

Conclusion: Multiple previous studies showed a better prognosis for MCC compared to PD/UD NMC. We, however, found stage 3 patients had a worse prognosis which may be secondary to higher comorbidities, increased stage, and higher rate of UD.