Toward the breast screening balance sheet: cumulative risk of false positives for annual versus biennial mammograms commencing at age 40 or 50

This study aimed to: (1) Estimate cumulative risk of recall from breast screening where no cancer is detected (a harm) in Australia; (2) Compare women screened annually versus biennially, commencing age 40 versus 50; and (3) Compare with international findings. At the no-cost metropolitan program studied, women attended biennial screening, but were offered annual screening if regarded at elevated risk for breast cancer. The cumulative risk of at least one recall was estimated using discrete-time survival analysis. Cancer detection statistics were computed. In total, 801,636 mammograms were undertaken in 231,824 women. Over 10 years, cumulative risk of recall was 13.3 % (95 % CI 12.7–13.8) for those screened biennially, and 19.9 % (CI 16.6–23.2) for those screened annually from age 50–51. Cumulative risk of complex false positive involving a biopsy was 3.1 % (CI 2.9–3.4) and 5.0 % (CI 3.4–6.6), respectively. From age 40–41, the risk of recall was 15.1 % (CI 14.3–16.0) and 22.5 % (CI 17.9–27.1) for biennial and annual screening, respectively. Corresponding rates of complex false positive were 3.3 % (CI 2.9–3.8) and 6.3 % (CI 3.4–9.1). Over 10 mammograms, invasive cancer was detected in 3.4 % (CI 3.3–3.5) and ductal carcinoma in situ in 0.7 % (CI 0.6–0.7) of women, with a non-significant trend toward a larger proportion of Tis and T1N0 cancers in women screened annually (74.5 %) versus biennially (70.1 %), χ² = 2.77, p = 0.10. Cancer detection was comparable to international findings. Recall risk was equal to European estimates for women screening from 50 and lower for screening from 40. Recall risk was half of United States’ rates across start age and rescreening interval categories. Future benefit/harm balance sheets may be useful for communicating these findings to women.