Screening behaviors, demographics, and stage at diagnosis in the publicly funded Ontario Breast Cancer Screening Program.

Abstract Purpose. The Ontario Breast Screening Program (OBSP) offers free screening mammograms every two years, to women aged 50-74. Study objectives were to determine demographic characteristics associated with adherence to OBSP and if women screened in OBSP have a lower stage at diagnosis than non-screened eligible women. Methods. We used the Ontario Cancer Registry (OCR) to identify 51,617 women, aged 50-74, diagnosed with breast cancer between 2010-2017. These women were assigned as screened (N=33,821) or non-screened (N=17,796) in OBSP. We used logistic regression to investigate the demographic characteristics associated with non-screening behaviour. We used multinomial regression to examine the association between screening status and stage at diagnosis.Results. Among women with breast cancer, those living in rural areas (versus the largest urban areas) had a lower odds ratio (OR) of not being screened (OR: 0.76, 95%CI: 0.72-0.81). Women in low income (versus high income) communities were more likely not to be screened (OR: 1.35, 95%CI: 1.27-1.43). When stratified, the association between income and screening status only held in urban areas. Non-screened women were more likely to be diagnosed stage II (OR: 1.76, 95%CI: 1.68-1.85), III (OR: 2.73, 95%CI: 2.56-2.92), or IV (OR: 6.93, 95%CI: 6.24-7.69) disease compared to stage I and were less likely to be diagnosed with ductal carcinoma in-situ (DCIS) (OR: 0.90, 95%CI: 0.85-0.96). Conclusions. This study suggests that targeting OBSP recruitment efforts to lower income urban communities could increase screening rates. OBSP adherent women were more likely to be diagnosed at earlier stages, supporting the value of this initiative and those like it.