Prognostic Impact of Tumor Status, Nodal Status and Tumor Sidedness in Metastatic Colon Cancer

Background Locally advanced primary tumors have been associated with poor overall survival (OS) in non-metastatic colon cancer. However, their impact on metastatic colon cancer (mCC) is not fully defined. The association between primary tumor location and prognosis in mCC is also evolving. Methods Using National Cancer Data Base, we identified a cohort of 25,377 patients diagnosed with mCC from 2004-2009. Chi-square test was used for descriptive analyses, while all potential prognostic factors were evaluated using Kaplan-Meier survival estimates and Cox proportional hazards regression modeling. Results The five-year OS for the entire study cohort was 12.3%. Factors associated with significant survival impact in multivariate analysis included age, gender, race, comorbidity index, academic level of treating institution, insurance status, income, year of diagnosis, primary tumor site, histologic differentiation, pathologic tumor stage (pT), pathologic nodal stage (pN), and modality of chemotherapy. pT1 lesions demonstrated poor prognosis in stage IV colon cancers, not statistically different when compared to survival outcomes observed in cases with pT4 lesions. Regional nodal involvement demonstrated poor OS in full cohort analysis and subgroup analysis independent of primary tumor location. Both right-sided and transverse colon tumors had similarly worse OS compared to left-sided tumors (right-sided: HR: 1.21, 95% CI: 1.17-1.25; transverse: HR: 1.21, 95% CI: 1.15-1.27). Conclusions T1 lesions arising from right-side or transverse colon portend a poor prognosis in mCC, while regional lymph node involvement by itself is an independent poor prognostic factor. Right-sided tumors are associated with poor outcomes than left-sided tumors, suggesting the role of underlying molecular or biologic variants.