CDX2 loss was a poor prognostic marker regardless of tumor side (left-sided 12 vs. 25 months and right-sided 8 vs. 22 months median OS, p < 0.001) and tumor grade (poorly differentiated 6 vs. 20 months, p < 0.001 and well/moderately differentiated 14 vs. 25 months median OS, p = 0.002) in patients treated with first-line combination chemotherapy. The gene discussed is CDX2; the disease is neoplasm.