Significance of histologic type of primary lesion and metastatic lymph nodes as a prognostic factor in stage III colon cancer

PURPOSE: This study was designed to investigate whether the histologic types of the primary lesion and of metastatic lymph nodes in Stage III colon cancer are useful as prognostic factors. The usefulness of adjuvant chemotherapy in a randomized, controlled trial by using these prognostic factors as stratification criteria was also investigated. METHODS: Stage III colon cancer patients were enrolled and were divided into two groups: Group W, in which the histologic type of both primary tumors and metastatic lymph nodes was well-differentiated adenocarcinoma; and Group U, in which the primary tumors and the metastatic lymph nodes were of any type other than well-differentiated. Group W patients were assigned to Treatment Arm A (surgery alone) or Arm B (surgery, then 1-hexylcarbamoyl-5-fluorouracil); and Group U patients, to Treatment Arm C (same as B), and Arm D (surgery + 1-hexylcarbamoyl-5-fluorouracil + mitomycin C). RESULTS: The Group W five-year survival rate was significantly superior to that in Group U (P = 0.0035). There was a better survival rate in Treatment Arm A than Arm B (P = 0.0321), but no difference between Treatment Arms C and D. CONCLUSIONS: In Stage III colon cancer, the prognosis of cases whose primary lesion and lymph node tissues are both well differentiated is extremely good. In such cases, it is possible for adjuvant chemotherapy to have a deleterious effect, and therefore, it is not recommended.