Body weight and prognosis in breast cancer.

We have examined the relationship between risk factors for breast cancer incidence and the subsequent prognosis of breast cancer among patients in a randomized controlled trial of adjuvant ovarian ablation. Body weight was the only risk factor found to be associated with statistically significant differences in survival. This finding could not be explained by a disproportionate number of anatomically more advanced tumors in the heavier women. In premenopausal women aged 45 years or more, the only group to benefit from adjuvant ovarian ablation, there was an interaction of treatment and weight, suggesting that weight exerts its influence on prognosis by a hormonal mechanism. The prognostic effect of weight was generally most marked in patients with tumors whose prognostic characteristics were favorable, and in these patients weight loss as an adjuvant treatment may reduce the frequency of disease recurrence.