Objectives: To compare attendance, recall and cancer detection as well as histopathological tumor characteristics among women attending BreastScreen Norway after a reminder versus an ordinary invitation.
Setting: This study was conducted on data from a population-based screening program inviting women aged 50-69 to biennial two-view mammography.
Methods: We used de-identified data from 883,020 women invited to BreastScreen Norway, 2004-2020, to analyze invitations, participation, recalls, biopsies, cancer detection, and histopathological tumor characteristics. All results were stratified by reminders and ordinary invitations. Early screening outcomes after reminders versus ordinary invitations were compared using bivariate tests and multivariable logistic regression.
Results: Reminders increased overall participation rate by 5.0%. The recall rate was 4.3% for reminded women and 3.3% for the ordinary invited. For reminded women, the rate of screen-detected cancer was 7.3 per 1000 screening examinations compared to 5.8 per 1000 for ordinary attenders. The interval cancer rates were 1.9 and 1.7 per 1000 for reminded and ordinary invited women, respectively. Median tumor diameter was 14 mm (interquartile range (IQR): 10-16) for screen-detected cancers (SDC) among reminded women and 13 mm (IQR: 10-16) for ordinary invited. A higher percentage of histological grade III cancers was observed among the reminded: 25.2% versus 21.7% for the ordinary invited. We also found a higher proportion of lymph node positive cases in those reminded: 23.6% versus 20.9%.
Conclusions: Postponing screening examinations affects early screening outcomes, including cancer detection and histopathological tumor characteristics. Women should be encouraged to attend screening at regularly intervals to avoid delays in diagnosis.
Keywords: Screening; breast cancer; mammography; participation; postal reminders; screening attendance.