Systematic review and meta-analysis of prognostic characteristics for breast cancers in populations with digital versus film mammography indicate the transition may have increased both early detection and overdiagnosis.

OBJECTIVE: Film mammography has replaced digital mammography in breast screening programs globally. This led to a small increase in the rate of detection, but whether the detection of clinically important cancers increased is uncertain. We aimed to assess the impact on tumour characteristics of screen-detected and interval breast cancers.

STUDY DESIGN AND SETTING: We searched seven databases from inception to 08 October 2023 for publications comparing film and digital mammography within the same population of asymptomatic women at population (average) risk of breast cancer. We recorded reported tumour characteristics and assessed risk of bias using the ROBINS-I tool. We synthesized results using meta-analyses of random effects.

RESULTS: Eighteen studies were included in the analysis from 8 countries, including 11,592,225 screening examinations (8,117,781 film; 3,474,444 digital). There were no differences in tumour size, morphology, grade, node status, receptor status, or stage in the pooled differences for screen-detected and interval invasive cancer tumour characteristics. There were statistically significant increases in screen-detected DCIS across all grades: 0.05 (0.00-0.11), 0.14 (0.05-0.22), and 0.19 (0.05-0.33) per 1,000 screens for low, intermediate, and high grade DCIS respectively. There were similar (non-statistically significant) increases in screen-detected invasive cancer across all grades.

CONCLUSION: The increased detection of all grades of DCIS and invasive cancer may indicate both increased early detection of more aggressive disease and increased overdiagnosis.

FUNDING: Australian National Health and Medical Research Council and the National Breast Cancer Foundation.

REGISTRATION: PROSPERO 2017:CRD42017070601.