The quality of breast cancer screening in Alberta

The Alberta Breast Cancer Screening Program (ABCSP), is an Alberta Health Services (AHS) program that provides screening mammograms to women aged 50 to 74*. It’s designed to detect breast cancer early, when treatment can be most effective.

ABCSP offers two options for Alberta women to have a screening mammogram. Women can choose to be screened at one of two AHS run Screen Test health centres in the province, or in one of their mobile units that serve rural communities.

The second option is for women to attend one of the many community radiology clinics across the province. The clinics are fee-for-service, billed directly to AHS. Most of the radiologists are affiliated with the Alberta Society of Radiologists, a voluntary professional association.

While both providers offer screening mammograms for the ABCSP program, researcher Yan Yuan has found differences in the quality of their performance—something she believes Alberta women should be aware of.

“Comparing important quality indicators of community radiology clinics to those of Screen Test, Screen Test performs significantly better,” states Yuan.

Yuan’s study used data from almost 400,000 ABCSP screening mammograms performed between 2006 and 2010 on women aged 50 to 69 years. Of those, 12.7 per cent were performed by Screen Test, and the remainder in community clinics.

Standard performance indicators were used to assess screening quality:

  • Abnormal recall rates
  • Benign biopsy rates
  • False positive rates
  • Positive predictive value (The percentage of screen-detected breast cancer diagnosed among all women who experienced abnormal recalls.)
  • Screen-detected cancer rates
  • Post-screen invasive cancer rate

“We split four years of data into two two-year study periods, to determine if there was quality improvement in the second period, after ABCSP was established in 2006,” explains Yuan. “There was no improvement.”

Overall, the community clinics had higher abnormal recall rate, false positive rates and benign biopsy rates. For example, for every 1000 screening mammograms completed in community clinics, 9.4 per cent were falsely interpreted as positive. In Screen Test centres, the false positive rate was only 3.4 per cent.   

“These inaccuracies can contribute to a woman’s stress about her health,” Yuan says. “That stress may deter her from future screening, impacting any benefits from early detection and treatment.” 

On the other hand, Screen Test was better at accurately detecting cancer—4.6 for every 1000 screens versus 3.6 in community clinics.

Quality results require quality equipment; rigorous technical standards; well-trained technicians performing mammograms; and trained, experienced radiologists to read and interpret images. While these can be present in both Screen Test and community clinics, Yuan believes Screen Test’s advantage may be found in its organizational structure.

“The centralization of services gives radiologists the opportunity to confer and collaborate on difficult cases in routine quality assurance meetings. AHS staff radiologists also get statistics as feedback on their own work.”

Quality assurance practices vary among community clinics, and it isn’t known if their radiologists are provided feedback to self-evaluate. Yuan also points out that, in many clinics, screening mammograms are not read separately from symptomatic diagnostic mammograms. The two require a different mindset, which may contribute to high inaccuracies observed in community clinics.

Yuan does not discourage eligible women from participating in ABCSP, but she says they may wish to also consider these findings when they schedule their next screening mammogram.

“For busy women, convenience is a factor when they decide where to book their mammogram,” she says. “Women should also consider these facts, and make a fully informed decision about where to schedule their next screening mammogram.”