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Breast Cancer Screening (Mammogram) Participation Methodology

Breast Cancer Screening (Mammogram) Participation
Short description of Indicator Age-adjusted percentage of Ontario screen-eligible women, 50 to 74 years old, who completed at least 1 mammogram within a 30-month period
Rationale for measurement There is strong evidence from clinical trials that breast cancer screening can reduce breast cancer mortality.[1] Observational evidence indicates that widespread adoption of mammography screening has contributed to a decline in mortality from breast cancer.[1] Adequate participation in breast cancer screening is essential for reductions in mortality to occur in the Ontario population.[2] [3] [4]
Evidence/references for rationale
  1. Nelson H, Fu R, Cantor A, Pappas M, Daeges M, Humphrey L.  Effectiveness of breast cancer screening: Systematic review and meta-analysis to update the 2009 U.S. Preventive Services Task Force Recommendation. Ann Intern Med. 2016;164:244–255. doi: 10.7326/M15-0969.
  2. Canadian Partnership Against Cancer.  Breast Cancer Screening in Canada: Monitoring and Evaluation of Quality Indicators- Results Report, December 2009–January 2010.  Toronto (ON): Canadian Partnership Against Cancer; 2015.
  3. Canadian Partnership Against Cancer. Report from the Evaluation Indicators Working Group: Guidelines for Monitoring Breast Cancer Screening Program Performance (3rd Edition). Toronto: Canadian Partnership Against Cancer; February, 2013.
  4. Coldman A, Phillips N, Wilson C, Decker K, Chiarelli A, Brisson J et al.  Pan-Canadian study of mammography screening and mortality from breast cancer.  J Natl Cancer Inst. 2014 Oct 1;106(8): pii: dju261.  Erratum in: J Natl Cancer Inst. 2015 Jan;107(1):dju404.
Calculations for the indicator (Total number of Ontario screen-eligible women, 50 to 74 years old, who completed at least 1 mammogram in a given 30-month period/ Total number of Ontario screen-eligible women, 50 to 74 years old in the reporting period) X 100
Standardized Rate Calculation 2011 Canadian population
Unit Percentage (%)
Data sources
  • ICMS (Integrated Client Management System) - OBSP mammograms
  • OHIP CHDB (Claims History Database) - Non-OBSP mammogram and mastectomy claims
  • OCR (Ontario Cancer Registry) - Invasive and in-situ breast cancers
  • RPDB (Registered Persons Database) – Demographics
  • PCCF+ - Residence and socio-demographic information
Time Frame 2010 - 2017
Geographic Scale Provincial (Ontario)
Denominator description Total number of Ontario screen-eligible women, 50 to 74 years old, in the reporting period
  • Ontario screen-eligible women ages 50 to 74 at the index date
  • Index date was defined as the midpoint in the reporting period, e.g., January 1, 2016 for 2016-2017
  • All mammograms in ICMS were counted, including those with partial views
  • The 2011 Canadian population was used as the standard population for calculating age-standardized rates
  • Exclusions:
  • Women with a missing or invalid HIN, date of birth, postal code or LHIN
  • Women with a prior diagnosis of invasive or in-situ breast cancer before January 1 of the reporting period; prior diagnosis of breast cancer was defined as: ICD-O-3 codes: C50, a morphology indicative of ductal carcinoma in-situ or invasive breast cancer, microscopically confirmed with a path report
  • Women with a mastectomy before January 1 of the reporting period. Mastectomy was defined in OHIP by fee codes E505, E506, E546, R108, R109, and R117
Numerator description Total number of Ontario screen-eligible women, 50 to 74 years old, who have completed at least 1 mammogram in a given 30-month period
  • Identifying mammograms:

OBSP mammograms for screening purposes were identified in the Integrated Client Management System (ICMS)

Non-OBSP mammograms were identified using fee codes in OHIP:

  • X178  (screening bilateral mammogram)
  • X185  (diagnostic bilateral mammogram)
  • Each woman was counted once regardless of the number of mammograms performed in a 30-month period; if a woman had both a program and non-program mammogram within a 30-month period, the program status was selected
Considerations  A small proportion of mammograms performed outside of OBSP as diagnostic tests could not be excluded from the analysis
Data availability & limitations
  • Historical RPDB address information is incomplete; therefore, the most recent primary address was selected for reporting, even for historical study periods
  • CHDB code X178 for screening bilateral mammography was introduced in October 2010
  • CHDB code X185 was used for both screening and diagnostic mammography prior to October 2010; since October 2010, X185 has been used for diagnostic mammography only; however, some screening mammograms after October 2010 may still use X185 for claims