Body size in relation to cancer of the uterine corpus in 1 million Norwegian women.

A positive association between overweight/obesity and endometrial cancer has been observed. It has been hypothesized that obesity is mostly associated with a subtype described as estrogen-dependent (Type I tumors), constituting about 80% of the endometrial tumors. Few epidemiologic studies have, however, analyzed different histological subtypes separately. The present study aimed at exploring the relations between body size and histological subtypes of cancer of the uterine corpus. Height and weight were measured in over 1 million Norwegian women aged 20-74 during 1963-2001. During follow-up, 9,227 cancers of the uterine corpus were diagnosed. The tumors were classified as Type I tumors (mostly endometrial adenocarcinomas with subgroups), Type II tumors (papillary, serous, and clear cell adenocarcinomas and some poorly differentiated carcinomas), sarcomas, and mixed tumors. Relative risks (RRs) of cancer of the uterine corpus were estimated using Cox proportional hazards regression. Compared with women with normal BMI, overweight and obese women had an overall RR of cancer of the uterine corpus of 1.36 (95% CI: 1.29-1.42) and 2.51 (95% CI: 2.83-2.66). The increase in risk was most pronounced for Type I tumors, but was also seen for Type II tumors, sarcomas and mixed tumors. The overall RR of corpus uteri cancer associated with a 10-cm increase in height was 1.09 (95% CI: 1.05-1.13), and was mostly observed for Type I tumors.