Relation of body mass index to tumor markers and survival among young women with invasive ductal breast carcinoma.

Background: Obesity has been shown to affect breast carcinoma prognosis, with the heaviest women having a higher mortality due to breast carcinoma. Few studies have focused on premenopausal women or the correlation of body mass index (BMI) to tumor characteristics related to prognosis.

Methods: The authors conducted a population-based follow-up study for mortality of 1177 women younger than 45 years of age who had invasive ductal breast carcinoma diagnosed from 1983 through 1992. Histologic slides and/or tumor tissue were collected for pathologic review, immunohistochemistry assays, and bivariate flow cytometric analysis.

Results: Women with breast carcinoma who were in the highest quartile of BMI were 2.5 times as likely (95% confidence interval [CI], 1.6-3.9) to die of their disease within 5 years of diagnosis compared with women in the lowest quartile of BMI. The tumors of the women in the highest quartile of BMI were more likely to be estrogen receptor negative (odds ratio [OR], 1.5; 95% CI, 1.0-2.2) and to have a high S-phase fraction (OR, 1.9; 95% CI, 1.2-3.1), high histologic grade (OR, 1.7; 95% CI, 1.0-2.9), high mitotic cell count (OR, 2.0; 95% CI, 1.2-3.1), and large tumor size (2 to < 5 cm: OR, 2.3; 95% CI, 1.5-3.1; or > or = 5 cm: OR, 2.7; 95% CI, 1.5-4.8) compared with the tumors of women whose BMI was in the first quartile. Relative to the large tumors (> or = 2 cm) in women in the lowest BMI quartile, the large tumors in women in the highest BMI quartile were more likely to express markers of high proliferation, indicating they may have grown faster than similar size tumors of the thinnest women. In a multivariate analysis including the tumor characteristics, obesity, as measured by being in the highest quartile of BMI, remained an independent prognostic factor for mortality (hazard ratio, 1.7; 95% CI, 1.0-2.9; P < 0.05.

Conclusions: Our study results indicated that being in the highest quartile of BMI was a strong predictor of mortality in women with breast carcinoma diagnosed at a young age. The tumors of the heavy women were larger and more likely to have markers of high cellular proliferation than those of thinner women.