Differences in colon and rectal cancer chemosensitivity

SUMMARY Adjuvant chemotherapy of rectal cancer is not well established. The aim of this review was to compare results of adjuvant treatment of colon and rectal cancer to identify possible clues for the differences in chemosensitivity. Adjuvant chemotherapy of 5-fluorouracil with folinic acid increased survival in colon cancer, but not in rectal cancer. A similar trend is seen for the addition of oxaliplatin. Using identical adjuvant treatment in colon and rectal cancer revealed a similar frequency of liver metastases, but a significant difference in the occurrence of lung (7.3 vs 12.7%) and peritoneal metastases (8.9 vs 4.0%). We hypothesize that the observed difference may be due to the influence of the microenvironment and differences in the expression of resistance genes such as the gene coding for thymidylate synthase. In conclusion, the differing effectiveness of adjuvant treatment of rectal and colon cancer may at least in part be caused by differing patterns of metastases associated with differing chemosensitivity.