Nepalese breast cancer in relation to reproductive factors: Comparison between Nepalese and Japanese cases

The characteristics of Nepalese breast cancer in relation to reproductive factors have not been studied. One hundred and nine Nepalese breast cancer patients were compared with 108 Japanese breast cancer patients and the expression of estrogen (ER) and progesterone receptor (PgR) was evaluated immunohistochemically, in 27 Nepalese breast cancer cases. In the Nepalese cases, the age at menarche was significantly older (14.1 vs 13.3 years), while the age at menopause was similar (49.0 vs 49.9 years). The mean age at first full-term pregnancy was significantly lower (20.6 vs 26.6 years), the average number of children was significantly larger (3.1 vs 2.1) and the cumulative duration of lactation was significantly longer (26.9 vs 17.1 months) in the Nepalese cases. In both groups, approximately 60% of breast cancer was premenopausal. The average age of Nepalese breast cancer patients, particularly premenopausal breast cancer patients, was significantly lower (38.6 vs 44.9 years). ER and PgR expression was 11% and 15%, respectively, in Nepalese breast cancer. Nepalese breast cancers were in an advanced stage when discovered. Nepalese breast cancer cases, particularly, premenopausal breast cancer patients, were seen at a relatively young age with late menarche, early first full-term pregnancy, long duration of lactation and a large number of children, when compared with Japanese cases. Breast cancer in Nepal may, involve mechanisms independent of estrogen exposure.