Sex differences in subsite incidence of large-bowel cancer.

A review of patients with large-bowel cancer at a major New Zealand hospital showed an excess of right-sided colonic tumors in females compared with males. These observations stimulated analysis of the National Cancer Registry registration data for large-bowel cancer for the whole of New Zealand in the years 1972 to 1975 (4678 patients). Rates for each site were calculated and age-standardized, using world population figures. The findings confirmed that females have a higher incidence of right-sided colonic cancer and males a higher incidence of rectal cancer and showed a significant trend in this direction from the ascending colon toward the rectum. The observed differences between males and females suggest differences in the etiology of the tumor and should be taken into account in assessing modalities and outcomes of treatment.