Risk factors of breast cancer in Burma.

A hospital-based case-control study of breast cancer was undertaken in Rangoon. The age-standardized incidence rate, 25.1 per 100,000 woman-years and the shape of the age-incidence curve show that Rangoon women have an intermediate level of breast cancer risk compared to women of other countries in the world. The analysis is based on 193 cases and 400 controls. Breast cancer risk was found to be directly related to educational attainment. There was an increased risk associated with early menarche and late menopause. The most striking finding was the strong inverse relationship between risk and parity; women who had six or more children have only one-third the breast cancer risk of married women who had less than four children. This association is not confounded by case-control differences in age at birth of first child. The association of breast cancer risk with age at first birth was not striking; only women with a first birth after age 30 were at increased risk. Breast cancer risk was unrelated to lactation. Overall, the epidemiology of breast cancer in Burma is similar to that in most other countries. However, the possibility of an unusual relationship of risk to parity and age at first parturition warrants further exploration.