Sidedness matters: Surrogate biomarkers prognosticate colorectal cancer upon anatomic location.

523Background: Recent evidence indicate that the anatomic location of primary tumors across the colon correlate with survival in the metastatic setting, whereas left-sided tumors may exhibit superior survival compared with right-sided. The Oncotype DX, a 12-gene colon cancer assay, is a clinically validated predictor of recurrence risk in stage II colorectal cancer (CRC) patients. Previous studies had indicated that CDX2-negative colorectal tumors are often associated with several adverse prognostic variables. Recently, it has been shown that without adjuvant chemotherapy, CDX2-negative stage II CRC tumors were associated with a lower rate of disease-free survival than CDX2-positive stage II CRC tumors. We aimed to evaluate whether these validated two prognostic biomarkers may correlate with primary tumor location, and whether tumor location may reflect differential prognosis in stage II CRC. Methods: We retrospectively analyzed a cohort of patients with T3 mismatch repair proficient (MMR-P) stage II CRC ...