Background: The value of mammographic screening in reducing breast carcinoma mortality among women younger than 50 years continues to be controversial. Previous randomized clinical trials have not been definitive because of inadequate sample sizes, prolonged screening intervals, questionable randomization, and/or cross-contamination between intervention groups. This study uses a historical prospective cohort design to examine differences in prognostic factors at the time of breast carcinoma diagnosis and differences in overall survival among patients ages 40-49 years, according to the method of breast carcinoma detection.
Methods: Women (n = 971) ages 40-49 years diagnosed with invasive breast carcinoma between 1986 and 1992 were identified by TUMORS (The Upper Midwest Oncology Registry Services). Measures of tumor size, lymph node status, and overall survival were compared with breast carcinoma patients whose tumors were detected by breast self-exam (BSE), clinical breast exam (CBE), patient incidental finding (PI), or mammography.
Results: Mean tumor size among women in the mammography group was smaller than that among women in the BSE, CBE, and PI groups (P < 0.002). Tumors detected by mammography were significantly more likely to be localized than those detected by other methods (P < 0.0001). Patients whose tumors were detected by mammography had significantly better survival than patients in the other detection method groups, especially among those with smaller tumors (P < 0.0001). This difference persisted even after adjustment for lead time bias.
Conclusions: Women ages 40-49 years whose invasive breast carcinoma is detected by mammography have significantly smaller tumors, more localized disease, and may have a lower risk of mortality than women whose tumors are detected by other methods.