Association of tumour site and sex with survival benefit from adjuvant chemotherapy in colorectal cancer

Adjuvant chemotherapy can improve 5-year survival in Dukes' C colorectal carcinoma. Improved selection of patients who will respond to adjuvant treatments is required. We investigated whether site of tumour origin, sex, and presence of microsatellite instability (MSI) phenotype were associated with a survival benefit from adjuvant chemotherapy. We analysed data for 656 consecutive patients with Dukes' C colorectal carcinoma, with median follow-up of 54 months (range 7–104) and mean age 66·7 years (SD 12·9). We screened tumour samples by PCR for deletions in the BAT-26 mononucleotide repeat to establish MSI status. Details of chemotherapy and survival were obtained by review of hospital and health-department records. Adjuvant chemotherapy (fluorouracil and levamisole) was given with curative intent to 272 (42%) patients. Striking survival benefits were seen for patients who had right-sided tumours and who received adjuvant chemotherapy compared with those who did not (48 vs 27% alive at end of study [95% Cl 0·25–0·56], p