THE EFFECTS OF A LOW-FAT DIETARY INTERVENTION AND TAMOXIFEN ADJUVANT THERAPY ON THE SERUM ESTROGEN AND SEX HORMONE-BINDING GLOBULIN CONCENTRATIONS OF POSTMENOPAUSAL BREAST-CANCER PATIENTS

The purpose of the study was to determine the effect of a low-fat diet ary intervention, with or without concomitant tamoxifen adjuvant thera py, on serum estrogen and sex hormone-binding globulin (SHBG) levels i n postmenopausal patients with resected breast cancer. Ninety-three pa tients were randomized to either reduce their fat intake to 15-20% of total calories, or to a dietary control group. Serum estradiol, estron e, estrone sulfate, and SHBG concentrations were assayed at baseline, and at 6, 12, and 18 months thereafter. In 19% of patients, the preint ervention serum estradiol levels were below the sensitivity of the ass ay (5 pg/ml). Tamoxifen had no significant effect on serum estrogen le vels, but produced an elevation in SHBG. Patients with reliably quanti fiable preintervention estradiol concentrations (greater than or equal to 10 pg/ml) showed a significant reduction in serum estradiol after 6 months on the low-fat diet (average, 20%; p < 0.005); this was susta ined over the 18 month study period. Serum SHBG levels were increased by tamoxifen therapy, but were reduced significantly (p = 0.01) after 12 months on the low-fat diet in patients not receiving tamoxifen. No changes in serum estrone or estrone sulfate resulted from the dietary intervention. While the low-fat diet produced significant weight loss, patients treated with tamoxifen without dietary intervention showed a gain in body weight. These weight changes produced disruptions in the normal positive correlation between body weight and serum estrone sul fate, and the negative correlation with SHBG concentration.