THE EFFECT OF BODY-MASS INDEX AND ESTROGEN-RECEPTOR LEVEL ON SURVIVALOF BREAST-CANCER PATIENTS

Background Epidemiological studies have demonstrated that obesity and low oestrogen receptor level adversely affect survival from breast can cer. Few studies have examined the joint effects of these variables. M ethods. A cohort study was conducted in which 1169 breast cancer patie nts from the Northern Alberta Breast Cancer Registry were followed for an average of 4.4 years. A number of variables related to breast canc er incidence and prognosis were studied. Body mass index (BMI) was use d as a proxy measure of obesity, Results. A Cox regression analysis re sulted in a final model with terms for size of tumour, number of posit ive axillary nodes, oestrogen receptor level, BMI, and age at diagnosi s, plus an interaction term for node status and BMI, Having relatively less oestrogen receptor increased the hazard ratio by 1.8 (95% CI : 1 .4-2.3); for women with no positive nodes, being in the highest quarti le of BMI increased the hazard ratio by 2.5 (95% CI : 1.2-5.2) compare d to the lowest quartile. Conclusions. BMI and oestrogen receptor leve l independently influence survival from breast cancer, but BMI affects survival only in patients with no positive axillary nodes.