ASSOCIATION OF BODY-FAT DISTRIBUTION AND FAMILY HISTORIES OF BREAST AND OVARIAN-CANCER WITH RISK OF POSTMENOPAUSAL BREAST-CANCER

The authors recently published data from a prospective cohort study of postmenopausal women (N Engl J Med 1992;326:1323-9) which suggested t hat a high waist/hip ratio was associated with a significantly increas ed risk of breast cancer in women with a positive family history of br east cancer. Since families with aggregations of breast and ovarian ca ncer demonstrate more consistent genetic linkage to markers on chromos ome 17q than do families with breast cancer alone, the authors perform ed additional analyses to examine whether the previously observed asso ciations with waist/hip ratio differed when family history of breast c ancer was partitioned according to whether or not ovarian cancer was a lso present in a close relative. Between 1986 and 1990, 620 incident c ases of breast cancer were identified in a cohort of 37,105 postmenopa usal Iowa women. A family history of breast cancer in first-degree rel atives was associated with a relative risk of 1.34 (95% confidence int erval (Cl) 1.07-1.69); a family history of both breast and ovarian can cer was associated with a relative risk of 2.36 (95% Cl 1.12-4.98). Co nsistent with the authors' findings after 4 years of follow-up, a high waist/hip ratio (greater than or equal to 80th percentile vs. <80th p ercentile) was associated with increased risk of breast cancer in the presence of a family history of breast cancer (relative risk (RR) = 2. 10, 95% Cl 1.43-3.09) but not in the absence of a family history of br east cancer (RR = 1.12). The combination of a high waist/hip ratio wit h a family history of breast and ovarian cancer was associated with 4. 83-fold increased risk (95% Cl 1.55-15.1). Neither a family history of breast cancer nor a family history of ovarian cancer was associated w ith significantly increased risk in the absence of a high waist/hip ra tio.