Poor Prognosis in Patients With Stage III Colorectal Cancer Receiving Adjuvant FOLFOX/CAPOX Therapy Is Predicted by the Presence of Many Poorly Differentiated Clusters

Poorly differentiated clusters (PDCs) have been reported to be a useful grading system for predicting prognosis in patients with colorectal cancer (CRC). We investigated the association between the number of PDCs and prognosis in patients with stage III CRC treated with oxaliplatin-based adjuvant chemotherapy.This is a retrospective study of 49 patients with stage III CRC who underwent curative surgery followed by oxaliplatin-based adjuvant chemotherapy. PDC was defined as a cluster of ≥5 cancer cells without glandular structure at the invasive front of the primary tumor.During the observation period, 12 patients experienced relapse. The patients were divided into two groups (<7 and ≥7 PDC groups), and receiver operating characteristic (ROC) curves were calculated [area under the curve (AUC)=0.743]. Patients with ≥7 PDCs had a much shorter relapse-free survival (RFS) than those with <7 PDCs (p<0.0001). The overall survival (OS) was also significantly worse in patients with ≥7 PDCs than in those with <7 PDCs (p<0.0001). Multivariate analysis revealed that PDC was the only significant prognostic factor measured that could predict RFS (p=0.002) and OS (p=0.0047) in patients with stage III CRC treated with oxaliplatin-based adjuvant chemotherapy.In patients with stage III CRC treated with post-resection oxaliplatin-based adjuvant chemotherapeutic regimens, the presence of ≥7 PDCs at the invasive front of the primary tumor predicted unfavorable prognosis.