Evaluating The Performance Of Mobile Units In A Breast Cancer Screening Program In São Paulo State, Brazil

Zoë GREENWALD, McGill University , Canada
LONGATTO-FILHO A. 3,5,6 , FREGNANI J. 3 , WATANABE A. 4 , FABIANA V. 3 , MATTOS J. 4 , FRANCO E. 1,2

1 Division of Cancer Epidemiology, McGill University, Montréal, Canada
2 Department of Oncology, McGill University, Montréal, Canada
3 Teaching and Research Institute, Barretos Cancer Hospital, Barretos, Brazil
4 Department of Prevention, Barretos Cancer Hospital
5 Laboratory of Medical Investigation (LIM-14), School of Medicine, University of São Paulo, São Paulo, Brazil
6 School of Health Sciences, University of Minho, Braga, Portugal

Purpose: To evaluate the impact of a population-based breast cancer screening programme implemented with mobile units in urban and rural regions of São Paulo state, Brazil, using performance indicators.

Methods: We studied women ages 40-49 screened annually and 50-69 screened biennially by two-view mammography on one of four mobile units in 2011-2015. We estimated coverage rates using census data. The hospital cancer registry was used to compare clinical characteristics at diagnosis of 656 screen-detected cases with 832 clinically-detected cases arising from the same population eligible for the screening program (aged 40-69 in regions serviced by the units).

Results: In total, 193,101 mammograms were performed on mobile units: 122,640 (63.5%) in initial screening and 70,461 (36.5%) in subsequent screening rounds. The average coverage rates were 35% among women ages 40-49 (annual) and 55% among women 50-69 (biennial). For initial and subsequent screenings, recall rates were 11.2% and 6.3% and cancer detection rates were 4.1/1000 and 2.1/1000, respectively. Biopsies were performed on 2,455 women. The positive predictive values were 18.3%, 29.6%, and 42.9% among women ages 40-49, 50-59, and 60-69, respectively. Breast cancer cases detected through the screening program had more favourable prognosis than clinically-detected cases, including smaller tumour size (53% vs. 36% of invasive tumours were <20mm), and a greater probability of detection below clinical stage II (Odds Ratio = 2.13, 95%CI: 1.69, 2.71).

Conclusions: Our findings show that a breast cancer screening program implemented with mobile units is a viable model for screening in urban and rural areas of Brazil. The mobile units increased access to cancer prevention services and the referral service was effective in guiding patients with suspected breast cancer through appropriate diagnostic steps.

Funding source: McGill Integrated Cancer Research Training Program, McGill Faculty of Medicine, McGill Institute for Health and Social Policy: McBurney, Mitacs Globalink Research Award