Breast cancer screening and diagnosis in British Columbia

Even though breast cancer is a major killer of women, especially women age 35 to 64, mortality rates have de­clined steadily since 1986.[1] This improvement has been attributed to two main factors:

• Increased screening, which has allowed for earlier and thus more effective intervention.
• Improved treatment with adjuvant therapies.

The Cancer Intervention and Sur­veillance Modeling Network of the National Institute of Health attempted to define the respective contributions of increased screening and advances in adjuvant therapies while accounting for changes in background risks.[2] 

The results of this modeling estimated that the observed mortality decline between 1990 and 2000 was 23.5% for women age 30 to 79. The decline in mortality due to screening and early intervention was 8% to 23%, while the decline due to improved adjuvant therapy was 12% to 21%.

Breast cancer is a heterogeneous disease. Specific molecular attributes of the disease must be identified before systemic treatment recom­mendations can be made. As adjuvant therapy options are now based on the specific pathological characteristics of tumors, the identification of these characteristics is a critically important part of the detection and initial diagnosis of cancer. 

Despite the decline in mortality rates, women in British Columbia have expressed deep concern about how the breast health system is organized.[3] According to a Canadian Breast Cancer Foundation study from 2001, both women and care providers see the process of obtaining a breast cancer diagnosis in BC as “emotionally troubling and structurally problematic.” Women describe their experience as a journey through a diagnostic “maze.”

Breast cancer epidemiology
The lifetime risk of breast cancer is 1 in 9 for women in BC.[4] Approximately 2700 BC women are diagnosed with breast cancer annually.[5] Incident rates have been relatively stable over time.[6] However, the demography of BC indicates that we will see higher incidence rates in the next few years. 

The number of women age 40 to 79 is expected to grow 21.4%, from 1020484 in 2007 to 1239286 in 2017.[7] Because breast cancer risk increases with age, the growth in this older age group, the 50 to 79 subgroup, will result in an increased incidence of cancer. 

BC Cancer Agency BCCA projections suggest that 2849 women will have been diagnosed with breast cancer in BC by 2007, and that this number will grow to 3619 by 2017, an increase of 27%.[8]

Breast health care guidelines
The BC Cancer Agency develops cancer management guidelines through various “tumor groups,” whose members review the latest evidence for the care of cancer types. Clinical guidelines developed by the BCCA focus on detection, diagnosis, and treatment paths. 

In BC women age 40 to 79 can refer themselves to the Screening Mammography Program (SMPBC). Women younger than 40 with a strong family history of breast cancer and women older than 80 require a referral to the program from a family doctor. The SMPBC recommends that women age 40 to 49 be screened every 12 to 18 months and women age 50 to 79 be screened every 2 years.

The current BCCA guidelines for diagnosis of breast cancer (available on the agency’s web site)[9] include the following recommendations:

• Diagnostic mammograms should be performed if there is any suspicious finding on a screening mammogram or if there is a palpable finding.

• Abnormalities detected by mammography may take the form of either a mass, a change in breast architecture, or abnormal calcifications within the breast. 

• If there is an abnormality that is not clearly malignant but is new, further imaging with additional views and magnification views should be un­dertaken.

• A suspicious new finding should be further assessed with imaging and a pathological diagnosis. A stereotactic core biopsy under mammographic guidance may be undertaken.

• If the diagnostic radiologist thinks the mass may be benign (e.g., there is a strong possibility it is a nonpalpable cyst or a small fibroadenoma), then an ultrasound examination may help distinguish between a cystic and a solid lesion. 

• If the lesion is likely cystic, then aspiration of the lesion under ultrasound control by the diagnostic radiologist may both diagnose and treat the abnormality, and may be all the treatment that is needed.

• If the lesion is found to be solid on ultrasound, or if the mammographic appearances are not clearly those of a benign abnormality, then one or more of the following are manda­tory, depending on the level of suspicion and on the size and discreteness of the lesion: fine needle aspiration under ultrasound guidance, stereotactic core needle biopsy, or open surgical biopsy guided by fine wire localization.

• A core biopsy is strongly recommended to obtain adequate tissue for pathological diagnosis and to plan surgical intervention if necessary. 

• Where a cluster of fine calcifications is identified and the diagnostic radiologist finds the appearance sufficiently suspicious, a stereotactic core needle biopsy or an open bi­opsy is required.

Given the current state of our knowledge about effective intervention, it is particularly important to consider health care service guidelines for population-based screening, high-risk screening, and diagnosis.

Population-based screening
The Public Health Agency of Ca­na­da (PHAC) reviewed international service guidelines for population-based screening in 1997.[10]  Table 1 uses the PHAC format to provide the most re­cent information about these guidelines.[5,11-14] For many of the indicators used, including the age group screened and the cancer detection rate, Canada’s standards are in line with those of other juris­dictions.

High-risk screening
Service guidelines also exist for screening high-risk populations, as shown in Table 2.[15-18] The inheritance of a BRCA1 or BRCA2 mutation places a woman at a 50% to 85% lifetime risk (to age 70) for developing breast cancer and a 40% to 60% risk for a second breast cancer once she has had breast cancer.[19,20] 

The contribution of BRCA1 and BRCA2 mutations in breast cancer populations, unselected for age and family history, has been examined in several studies reporting mutation frequencies be­tween 1% and 12%.[21] The wide range is a reflection of the fact that the frequency of BRCA1 and BRCA2 mutations in women with breast cancer varies according to the age at diag­nosis, family history of cancer, and ethnicity or country of origin. 

At present most genetic screening is for the BRCA1 and BRCA2 gene mutations only; however, some work on screening for CAG trinucleotide repeat sequences is being explored in certain jurisdictions.[22] Other factors that put a woman at a greater than 20% risk of developing breast cancer should be considered in a similar fashion. This includes treatment with mantle (chest) radiation for Hodgkin disease before the age of 25.[23]

Diagnosis
The diagnostic phase of the breast health care system is unlike the screening phase. In Canada diagnosis usually occurs in public or radiologist-led facilities. In Europe diagnostic services are frequently part of a specialized breast unit, and service guidelines have been developed in support of this part of the system.  Table 3 summarizes diagnosis guidelines used in Europe and the United Kingdom.[23-25] 

Unfortunately, these service guidelines do not distinguish between core and fine needle for biopsies—information that would be useful, given that observational studies have shown core biopsy to have higher unequivocal results than fine needle biopsy (85% vs 62%) but also higher false-negative rates (13% vs 6%).[27-29]

Breast health service utilization in BC
In 2005, 256942 screening mammograms were performed in BC.[5] Although all women age 40 to 79 are eligible to participate in the provincial screening mammography program without a doctor’s referral, only 42% of eligible women actually did participate. 

In the 50 to 69 age group only 49% of eligible women participated. Consequently, only 38% of breast cancers diagnosed in 2005 were the result of screening. The figure summarizes the utilization of diagnostic services in BC, beginning with the 18573 mam­mograms and the 74351 direct referrals that led to diagnostic mammograms and further workup.[5]

The Canadian benchmark for screening mammography announced in December 2005 specifies that 70% of women age 50 to 69 should have a screening mammogram every 2 years. The Screening Mammography Program of BC has submitted a plan to the Ministry of Health to reach this target by 2017. 

The main challenges are the high number of nonparticipants, a system-wide shortage of mam­mography technologists, and the need to convert to digital format. The 10-year plan involves performing 16000 more screens a year. 

More screening means that an estimated 2640 more patients will need diagnostic mammograms, 211 more patients will need surgical biopsy, and 84 more cancers will be diagnosed—mostly cancers that would have been found at later stages in the absence of a screening program.

Best practices versus current practices
Table 4 compares the European and Canadian best practice guidelines with the current screening practices in BC, Ontario, and the UK.[5,30,31] There are a few causes for concern, beginning with BC’s low attendance rate for screening mammography, which is lower than Ontario’s performance in the 50 to 69 age group. 

In fact, both Ontario and BC fall far short of the Canadian and European targets for the 50 to 69 population. The UK, in contrast, has been able to meet these targets. 

Once women enter the screening program in BC, the retention rates meet Canadian standards of more than 75% within 30 months. The European target, however, is higher and the Canadian target may reflect awareness of how hard it is to provide service to a small population spread over a large area. 

We see this in the fact that health service delivery areas in BC have widely varying rates of participation from a low of 30% in the East Kootenays to a high of 57% in the Okanagan.[32] To effectively reduce mortality from breast cancer in the population, it is essential to improve utilization of screening mammo­graphy. A projected 30% mortality reduction from screening is based on screening 70% of women age 50 to 69. 

The abnormal recall rate from screening (i.e., the proportion of screens requiring additional diag­nostic workup) is higher in BC than the Canadian and European targets suggest. The Canadian standard is not as rigorous as the European one, and although the current practice in the UK would meet the Canadian standard, it too does not meet the European target. 

BC’s higher abnormal recall rate likely reflects a conser­vative approach and no doubt contributes to the higher proportion of biopsies being conducted on benign masses. There is room for improvement with respect to the specificity of the service, which may be resulting in overservice at present.

Another potential source of concern not included in Table 4 is the proportion of women who have a preoperative diagnosis of cancer. In BC this is about 64% at present, compared with a European target of more than 90%. In the UK the proportion is 80.5% for initial screens and 86.8% for subsequent screens. This means that women in BC are undergoing more invasive procedures to receive a definitive diagnosis.

Overall, the current BC screening system is effectively detecting cancer (exceeding both European and Canadian guideline requirements) and is also detecting invasive cancers while they are small and thus more amenable to treatment resulting in positive outcomes. 

However, we still lack information in several key areas. We do not know the utilization rates of triple assessment (clinical evaluation, imaging, and biopsy),which is still regarded as the criterion standard. We do not know how the use of core biopsy compares with fine needle aspiration. This is important because core biopsy permits the collection of more tissue than fine needle aspiration does, and provides information necessary for treatment decisions, including whether the disease is invasive or in situ and the patient’s estrogen and HER2 status. 

Even though this information is needed for determining adjuvant therapy, we do not know the percentage of cases where this information is collected and we do not routinely collect data that allows us to evaluate compliance with this guideline. 

With respect to high-risk populations, pa­tients who are BRCA1 or BRCA2 carriers or who have had mantle radiation for Hodgkin disease at a young age should be having annual MRIs; however we do not know whether these women are receiving this service.

Conclusions
In BC participation in population-based screening falls below the level recommended by international guidelines. Only 49% of the 50 to 69 age group receive mammograms, well below the 70% recommended in 2005 for Canada. 

Because many BC women do not receive mammograms, only 38% of cancers are diagnosed through the screening program. Women in BC are also undergoing more diagnostic procedures than required to receive a diagnosis: 15% are recalled after initial screening in contrast to the Canadian standard of 10% and the European standard of 7%. 

In addition, women in BC are having surgery with an open biopsy to receive a definitive diagnosis at a higher rate (36%) than current guidelines, including our BC recommendations, would suggest is appropriate (<10%). 

At present the outcomes for breast cancer patients in industrialized na­tions are excellent. The 5-year survi­val rate for women diagnosed in BC with breast cancer in 2000 is 88%.[33] A recent study of breast cancer in Europe explored 5-year survival of patients diagnosed in 1995. The 5-year survi­val for all European countries was 79.5%, with lows of 70% in the Czech Republic and Slovenia, and highs of 88% in Iceland.[34] (In contrast, the 5-year survival in BC for the same period was 86%).[35] 

The present good outcomes for breast cancer patients in BC are the result of a screening and diagnosis system based on what was best practice 10 years ago. To ensure that BC continues to be among the jurisdictions with the best outcomes in the world, we must avail ourselves of new knowledge and update our provincial practices accordingly. 

Enhanced use of core biopsy to provide tissue samples for determining tumor features and planning treatment is a key element of the contemporary diagnostic process for breast cancer. To improve survival rates for breast cancer further will require both greater participation in screening, particularly in women age 50 to 69, and better access to core biopsy and tumor marker pathology.

Competing interests
None.

Ms Poole is a health service policy and research analyst with the BC Cancer Agency (BCCA) and a doctoral student in the School of Health Care and Epidemi­ology at the University of British Columbia, under the supervision of Dr Charlyn Black. Dr Gelmon is the former head of the Breast Tumour Group at the BCCA. Dr Borugian is a scientist with the BCCA. Ms Kan is the operations leader of screening programs at BCCA. Dr Stilwell is president of the Canadian Breast Cancer Foundation, BC/Yukon division.