Accuracy of screening mammography varies by week of menstrual cycle

Purpose: To investigate sensitivity, specificity, and cancer detection rate of screening mammography according to week of menstrual cycle among premenopausal women. Materials and Methods: In this institutional review board - approved HIPAA-compliant study, sensitivity, specificity, and cancer detection rate of 387 218 screening mammograms linked to 1283 breast cancers in premenopausal women according to week of menstrual cycle were studied by using prospectively collected information from the Breast Cancer Surveillance Consortium. Logistic regression analysis was used to test for differences in mammography performance according to week of menstrual cycle, adjusting for age and registry. Results: Overall, screening mammography performance did not differ according to week of menstrual cycle. However, when analyses were subdivided according to prior mammography, different patterns emerged. For the 66.6% of women who had undergone regular screening (mammography had been performed within the past 2 years), sensitivity was higher in week 1 (79.5% ) than in subsequent weeks (week 2, 70.3%; week 3, 67.4%; week 4, 73.0%; P = .041). In the 17.8% of women who underwent mammography for the first time in this study, sensitivity tended to be lower during the follicular phase (week 1, 72.1%; week 2, 80.4%; week 3, 84.6%; week 4, 93.8%; P =.051). Sensitivity did not vary significantly by week in menstrual cycle in women who had undergone mammography more than 3 years earlier. There were no clinically meaningful differences in specificity or cancer detection rate. Conclusion: Premenopausal women who undergo regular screening may benefit from higher sensitivity of mammography if they schedule screening mammography during the 1st week of their menstrual cycle.