CTF Structured Abstract: Screening for breast cancer

Canadian Task Force on Preventive Health Care

Structured Abstract

Screening for Breast Cancer

Prepared by Brenda J. Morrison, PhD, Professor, Department of Health Care and Epidemiology, University of British Columbia, Vancouver, BC

These recommendations were finalized by the Task Force in January 1994

Objective
Burden of Suffering
Options
Outcomes

Evidence
Values
Benefits, Harms, and Costs
Recommendations

Validation
Sponsors
Selected References

Objective

To make recommendations about screening for breast cancer in asymptomatic women aged 40 to 49 years and 50 to 69 years in Canada.

Burden of Suffering

Breast cancer is the third most common cause of death in women in Canada and excluding skin cancer is the most common cancer in women in Canada. There were an estimated 16,300 new cases of breast cancer in Canada in 1993 and an estimated 5,400 deaths. Over the last 20 years the incidence rate has increased by about 15% whereas the mortality has remained relatively stable.

Within Canada, there is an east-west gradient with lower rates in the east. Risk factors for breast cancer include hormonal, dietary and hereditary factors. Early menarche, late menopause and delayed first pregnancy are associated with higher risk. There is some evidence linking high intake of dietary fat to risk of breast cancer; family history, obesity, alcohol use, ionizing radiation and post-menopausal estrogen replacement therapy have also been associated with increased risk, while the evidence for oral contraceptives is more controversial.

Options

Screening methods were clinical breast examination, mammography and breast self-examination (BSE).

Outcomes

Main outcome was mortality, indicated by mortality or survival rates. Other outcomes included factors associated with improved survival (stage, tumour size, axillary node involvement). Sensitivity and specificity of tests were also reported.

Evidence

Data sources included a MEDLINE search in November 1993 using the keywords "breast neoplasms", "mass screening", "guideline", "familial or genetic markers"; and a search of the author’s personal files.

Recommendations were graded as:

A Good evidence to support the recommendation that the condition be specifically considered in a PHE.

B Fair evidence to support the recommendation that the condition be specifically considered in a PHE.

C Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.

D Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

E Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

Quality of evidence was rated according to 5 levels:

I Evidence from at least 1 properly randomized controlled trial (RCT).

II-1 Evidence from well-designed controlled trials without randomization.

II-2 Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.

II-3 Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.

III Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.

Values

The 13-member Task Force of experts in family medicine, geriatric medicine, pediatrics, psychiatry and epidemiology used an evidence-based method for evaluating the effectiveness of preventive health care interventions. Recommendations were not based on cost-effectiveness of options. Patient preferences were not discussed.

Background papers providing critical appraisal of the evidence and tentative recommendations prepared by the chapter author were pre-circulated to the members. Evidence for this topic was presented and deliberated upon in 1- to 2-day meetings, 2 to 3 times per year from January 1993 to June 1993. Consensus was reached on final recommendations.

Benefits, Harms, and Costs

Sensitivities and specificities for detection were 46% to 88% and 82% to 99.9% respectively, and varied by screening method, screening interval length, incidence of disease and method of calculating estimates of screening proficiency. In a Canadian trial, the sensitivity of annual mammography plus clinical examination (based on ratio of screen-detected cases to all cases) was 88% in women aged 50 to 59 years and 81% in women 40 to 49 years. Specificity (using surgical biopsy as gold standard) ranged from 96.5% to 99.9%.

7 RCTs examined screening using clinical examination and/or mammography in women aged 40 to 74 years, randomized by individual or by neighbourhood or practice clusters. All found reductions in mortality in women over aged 50 – 69 years of age. None found significant benefits for women aged 40 to 49 years (relative risks ranged from 0.51 to 1.36).

5 studies reported an association between BSE and factors associated with better survival (stage, tumour size, axillary node involvement); 2 found no benefit. Cohort studies suggest decreased mortality among women who practice BSE, although these results may reflect lead-time, length-time and self-selection biases.

Recommendations

Recommendation grade [A, B, C, D, E] and level of evidence [I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations in support of individual recommendations are identified in the guideline text.

There is good evidence for screening, during the PHE, asymptomatic women aged 50 to 69 years using clinical examination and mammography [A, I].
There is fair evidence to exclude, from the PHE, screening asymptomatic women aged 40 to 49 years using routine clinical examination and mammography [D, I].*Note: This recommendation has been updated.
Link to Recommendation Table of 2001 Update: Screening mammography among women aged 40-49 years at average risk of breast cancer
There is insufficient evidence to include or exclude teaching of breast self-examination [C, II-2].*Note: This recommendation has been updated.
Link to Recommendation Table of 2001 Update: Should women be routinely taught breast self-examination to screen for breast cancer?

Validation

This report was externally peer reviewed. This paper was externally peer-reviewed.. Recommendations differ from those of the U.S. Preventive Services Task Force (1992 version); however, these have since been updated to reflect recent follow-up trials.

Selected References

Source Document

Morrison BJ. Screening for breast cancer. In: Canadian Task Force on the Periodic Health Examination. Canadian Guide to Clinical Preventive Health Care. Ottawa: Health Canada, 1994; 788-95.

Other

Canadian Task Force on the Periodic Health Examination: The periodic health examination: 2. 1985 update. Can Med Assoc J 1986;134:724-9.

Link to Full Text of this review

Link to Summary Table of Recommendations of this review

Link to Selected References list of this review

Link to 2001 Update: Breast Self-Examination to Screen for Breast Cancer

Link to 2001 Update: Screening mammography among women aged 40-49 years at average risk of breast cancer

Link to 1999 Update: Follow-up after breast cancer

Link to 1998 rewording of recommendation for screening women aged 50-59 for breast cancer

Top of Page

CTFPHC Home Page

A	Good evidence to support the recommendation that the condition be specifically considered in a PHE.
B	Fair evidence to support the recommendation that the condition be specifically considered in a PHE.
C	Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.
D	Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.
E	Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

I	Evidence from at least 1 properly randomized controlled trial (RCT).
II-1	Evidence from well-designed controlled trials without randomization.
II-2	Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.
II-3	Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.
III	Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.