Differences in breast cancer diagnosis by patient presentation in Ontario: a retrospective cohort study

Note: CI = confidence interval, ER = estrogen receptor, HER2 = human epidermal growth factor receptor 2, NA = not applicable, NOS = not otherwise specified, O-BAS = OBSP-affiliated breast assessment site, OBSP = Ontario Breast Screening Program, OR = odds ratio, PR = progesterone receptor, Ref. = reference category.

↵* n = 49 420; findings derived from a multinomial logistic regression adjusted for all variables in the table and Local Health Information Network. The p value is from a single multinomial multivariable model, representing the overall difference between the 3 groups (symptomatic v. OBSP-screened v. non-OBSP-screened), with the symptomatic group as the reference.

↵† Adapted from Statistics Canada Postal Code Conversion File and Postal Code Conversion File Plus (June 2017), which is based on data licensed from Canada Post Corporation.16 We used the patient’s postal code at diagnosis.

↵‡ Odds ratios reflect the odds of diagnosis in an O-BAS for every 100-km increase in Euclidean distance to the patient’s closest O-BAS. We used the patient’s postal code at diagnosis.

Note: CI = confidence interval, ER = estrogen receptor, HER2 = human epidermal growth factor receptor-2, NOS = not otherwise specified, O-BAS = OBSP-affiliated breast assessment site, OBSP = Ontario Breast Screening Program, OR = odds ratio, PR = progesterone receptor, Ref. = reference category.

↵* Diagnostic interval is the time from suspicion of breast cancer until diagnosis (overall mean 62 d, standard deviation [SD] 65.6 d; median 35 d, interquartile range [IQR] 19–82 d). Pre-treatment interval is the time from diagnosis of breast cancer until first treatment (overall mean 38 d, SD 29.5 d; median 34 d, IQR 23–47 d.

† Adjusted for O-BAS status, screening status, age, neighbourhood income quintile, neighbourhood immigrant density, rurality, distance to the closest O-BAS, Charlson Comorbidity Index, previous breast cancer, laterality, cancer stage, hormone receptor profile, topography, year of diagnosis and level of geography (Local Health Integration Network). β coefficients reflect the effect of a 1-unit change in the patient or tumour characteristic on the duration of the time interval, in days.

↵‡ Adapted from Statistics Canada Postal Code Conversion File and Postal Code Conversion File Plus (June 2017), which is based on data licensed from Canada Post Corporation.16 We used the patient’s postal code at diagnosis.

↵§ β coefficients reflect the effect of a 100-km change in Euclidean distance to the patient’s closest O-BAS. We used the patient’s postal code at diagnosis.

Note: IQR = interquartile range, O-BAS = OBSP-affiliated breast assessment site, OBSP = Ontario Breast Screening Program,

↵* We collected health care encounter and timing of health care encounter relative to the diagnosis date from the Ontario Cancer Registry. We included encounters if they occurred within 6 months before diagnosis until the start of treatment (or 60 days after diagnosis, if no treatment). We identified encounters using billing codes from the Ontario Health Insurance Program, or procedural codes from the Discharge Abstract Database (inpatient) and the National Ambulatory Care Reporting System (outpatient).

↵† Positive values indicate the encounter occurred before diagnosis; negative values indicate the encounter occurred after diagnosis.