Stratification of Stage III colon cancer may identify a patient group not requiring adjuvant chemotherapy

Adjuvant chemotherapy for colon cancer with lymph node involvement (Stage III) has been the standard of care since the 1990s. Meanwhile, considerable evolvement of surgery combined with dedicated histopathological examinations may have led to stage migration. Furthermore, prognostic factors other than lymph node involvement have proven to affect overall survival. Thus, adjuvant chemotherapy in Stage III colon cancer should be reconsidered. The objective was to compare recurrence rates and survival in stage III colon cancer patients treated with or without adjuvant chemotherapy. Further, to assess the impact of extensive mesenterectomy, lymph node stage and vascular invasion on outcome.

Consecutive patients operated for Stage III colon carcinoma between 31 December 2005 and 31 December 2015 were identified in the pathological code register by matching colon (T67) and either adenocarcinoma (M81403) or mucinous adenocarcinoma (M84803), with lymph node (T08) and metastasis of adenocarcinoma (M81406 or M84806). Medical records of all identified patients were reviewed.

Of 216 identified patients, 69 received no postoperative adjuvant chemotherapy (group NC), 69 insufficient adjuvant chemotherapy (FLV or < minimum recommended 6 cycles FLOX, group IC), and 78 sufficient adjuvant chemotherapy (≥ 6 cycles FLOX, group SC). When adjusted for age and comorbidity, 5-year overall survival did not differ statistically significant between groups (76% vs. 83% vs. 85%, respectively). Vascular invasion and a high lymph node ratio significantly reduced overall survival.

The findings imply that subgroups of Stage III colon cancer patients have good prognosis also without adjuvant chemotherapy. For definite conclusions about necessity of adjuvant chemotherapy, prospective trials are needed.