BODY-MASS AND BREAST-CANCER - RELATIONSHIP BETWEEN METHOD OF DETECTION AND STAGE OF DISEASE

BACKGROUND. Obesity is associated with advanced stage breast cancer at diagnosis and a poorer prognosis. Stage of breast cancer at diagnosis is also strongly influenced by the method of cancer detection. The ob jective of this study was to determine the relationship between body m ass index (BMI) and breast cancer disease stage, taking into account t he method of cancer detection (i.e., self-detection, screening mammogr aphy, and clinical breast examination [CBE]). METHODS. From 1988 to 19 90, 2863 patients with invasive breast cancer were identified through a statewide, population-based, cancer reporting system and were interv iewed as part of a larger study of breast cancer etiology. Stage of di sease was classified as either localized or nonlocalized (regional and distant disease combined). The relation between BMI and disease stage was examined by using multiple logistic regression adjusting for age, education, race, year of diagnosis, and prior mammography use. RESULT S. Thirty-eight percent (1092 of 2863) of the women had nonlocalized b reast cancer. A strong dose-response relationship was observed between increased BMI and the likelihood of nonlocalized disease (P < 0.001). However, this association was present only among the 55% of women (15 85 of 2863) who self-detected their tumors. The odds ratios for nonloc alized cancer increased from 1.0 for the lowest quintile of BMI to 1.3 , 1.6, 1.7, and 1.8 for the second through fifth quintiles, respective ly, for this group. CONCLUSIONS. Greater body mass was associated with nonlocalized breast cancer; however, this association was restricted to women who detected their own can eer. No association was found betw een BMI and stage of disease among cases detected by either mammograph y or CBE. Cancer 1996; 77:301-7. (C) 1996 American Cancer Society.