Bilateral breast cancer and familial aggregations

Abstract

Bilateral breast cancer and familial aggregation among Japanese female patients with breast cancer were studied and results were compared with those among American female patients. Out of 3365 female patients with breast cancer mastectomized at the Cancer Institute Hospital, Tokyo from 1946 to 1975, 92 cases were primary bilateral breast cancer. The crude incidence of bilateral cancer was 2.7%, whereas it was reported to range between 3.0% and 6.8% among American female patients. The true incidence rate of breast cancer after operation for unilateral breast cancer was calculated to be 3.4 per 1000 Japanese patients per year, while it was reported to be between 5.8 and 7.1 among American patients. These figures for American patients are roughly twice as large as those for Japanese females. In the bilateral breast cancer group, there was a high frequency of familial history of breast cancer, about three times higher than that in the unilateral breast cancer group. Further, in the bilateral breast cancer group, about half of the patients were nulliparous and 60% of the patients had breast cancers associated with fibrocystic disease in the same breast tissues. These figures were about three times greater than for those in the unilateral breast cancer group.