Objective: To compare breast characteristics, compression parameters, and early performance measures (rates of recall, screen-detected and interval breast cancer, and histopathologic tumour characteristics) for mammographic screening at a stationary versus mobile screening unit.
Methods: Results from 92,408 mammographic screening examinations performed as part of BreastScreen Norway during 2008–2017 at either a stationary (n = 52,620) or mobile (n = 39,788) unit in Hordaland county were compared using descriptive statistics and generalized estimating equations. A generalized estimating equation for a binary outcome was used to estimate crude and adjusted odds ratios with 95% confidence intervals for the outcomes of interest. Adjusted generalized estimating equation models included age, breast volume, and density grade as covariates.
Results: Screening at the stationary unit was performed on smaller breasts with higher mammographic density, using lower compression force but higher pressure than at the mobile unit. Using the stationary screening unit as reference, for women screened at the mobile unit, the adjusted odds ratio was: for recall 0.94 (95% CI: 0.87--1.01), screen-detected breast cancer 0.92 (95% CI: 0.78--1.10), and interval breast cancer 1.17 (95% CI: 0.83–1.64).
Conclusions: The quality of care did not differ for women screened at the stationary versus the mobile unit, but there were differences between the women who attended the two units. Sociodemographic factors should be included in future analyses to fully understand the risk of breast cancer among women residing in urban versus rural areas.
Keywords: Mammography; breast cancer; breast characteristics; breast compression; cancer screening; early detection of cancer; early performance measures; health service; mass screening; socioeconomic factors; urban/rural.