Breast Cancer Screening Paul Jones, PGY2 Resident Rounds 25 July 2012
Objective To review the current evidence and guidelines for Breast Cancer screening among women of average risk of disease (defined as those with no previous breast cancer, no history of breast cancer in a first- degree relative, no known mutations in the BRCA1/BRAC2 genes or no previous exposure to chest wall radiation).
The Trouble With ‘Doctor Knows Best’ "It is time for us to own up to our shortcomings in cancer screening, and we must start by acknowledging a hard fact: Doctors sometimes don’t know best. We are terrific at inventing new tests that can be performed on people. But we have been less good at figuring out which people should have them." The Trouble With ‘Doctor Knows Best’ by Peter B. Bech, MD. From the New York Times, June 4 2012. The Trouble With ‘Doctor Knows Best’
Prevalence In 2012, approximately 88,800 Canadian women will be diagnosed with cancer, and an estimated 36,200 women will die of cancer. Breast cancer accounts for over a quarter (28%) of new cancer cases in women.
Major Risk Factors Being aged 50 or older. Dense breast tissue as shown by a mammogram. Breast density is often lower as women age and after menopause. Having a previous breast tissue sample (biopsy) that showed cells that look abnormal (atypical hyperplasia). A mother or sister with breast cancer especially if they learned they had breast cancer before age 50. If more than one immediate family member had breast cancer, or if your family has a history of ovarian cancer. Some families may have mutation of a breast cancer gene (a permanent change in the DNA of either of the genes known as BRCA1 or BRCA2). Repeated radiation to the chest due to treatment of a disease (such as Hodgkin's). The risk is highest if you were exposed to the radiation between ages 13 to 30.
Minor Risk Factors Not having any children or being more than 30 years old when a first child was born. Starting your monthly periods (menstruation) before age 12. Late menopause (after age 55). Current use of hormone replacement therapy that totals 5 years or more. Current use of the birth control pills and for 10 years after you stop taking them. Overweight after menopause. Having more than one drink of alcohol per day.
Breast Self-Examination (BSE) “Despite a significant increase in the number of breast cancers detected when BSE instruction was provided, there was no reduction in all-cause mortality.” “Meta analysis of BSE randomized trials and non- randomized studies also indicate no significant difference in breast cancer mortality between BSE and control groups.” Screening for Breast Cancer: Systematic Evidence Review Update from the U.S. Preventive Services Task Force. Ann Intern Med. 2009 November 17; 151(10):727-W242.
Clinical Breast Exam (CBE) Few trails examine the effectiveness of CBE. The Canadian National Breast Screening Study-2 (CNBSS-2) trial comparing mammography with CBE versus CBE alone, showed no difference in mortality between these two approaches. Screening for Breast Cancer: Systematic Evidence Review Update from the U.S. Preventive Services Task Force. Ann Intern Med. 2009 November 17; 151(10):727-W242.
Mammogram Sensitivity 77-95% SnOut - Sensitivity allows you to rule out. Specificity 94-97% SpIn – Specificity allows you to rule in.
Assumption Early detection, leads to early treatment, which will reduce morbidity and mortality.
Benefits Early diagnosis Peace of mind Catching cancer at an early stage and simpler treatment Breast Cancer Mortality Reduction All-Cause Mortality Reduction
Harms Radiation Exposure Pain during Procedures Anxiety, Distress, and Other Psychological Responses False Positive and Negative Mammograms, Additional Imaging, and Biopsies No improvement to your length and/or quality of life and unnecessary diagnosis ?Over diagnosis
So what? Screening is likely to reduce breast cancer mortality. As the effect was lowest in the adequately randomized trials, a reasonable estimate is a 15% reduction corresponding to an absolute risk reduction of 0.05%. Screening led to 30% over diagnosis and overtreatment or an absolute risk increase of 0.5%. Screening for breast cancer with mammography (Review) 2011 The Cochrane Collaboration.
So what? For every 2000 women invited for screening throughout 10 years, 1 will have her life prolonged 10 healthy women, who would not have been diagnosed if there had not been screening, will be treated unnecessarily. Furthermore, more than 200 women will experience important psychological distress for many months because of false positive findings. Screening for breast cancer with mammography (Review) 2011 The Cochrane Collaboration.
Canadian Task Force on Preventive Health Care Guidelines Breast Self-Examination Recommend not advising women to practice breast self-examination. Clinical Breast Exam Recommend not routinely performing clinical breast examination alone or in conjunction with mammography to screen for breast cancer. Mammography 40-49 recommend not routinely screening 50-69 years recommend routinely screening ever 2 to 3 years 70-74 years recommend routinely screening ever 2 to 3 years MRI Recommend not routinely screenin with MRI scans.
Handouts Pt Hand Outs Women 50-69 years – PBSG Appendix 3: Canadian Task Force on Preventive Health Care recommendation for screening for breast cancer with mammography.
“Nunc cognosco ex parte” – “Now I know in part”
Is the decision to recommend reduced breast screening ethical? “Can we put a maximum price on health-care resources, without putting a price on life?” “We should recognize mistakes as to the causation of both beneficial and harmful outcomes, and in assuming that people in white coats always benefit us health-wise.” Margaret Somerville
Conclusion No simple answers, you must draw your own conclusions. My recommendation: Talk to your patient about the benefits and risks of screening to help them make an informed choice. Suggest the resource “Information on Mammography for Women Aged 40 and Older - A Decision Aid for Breast Cancer Screening in Canada” from the Public Health Agency of Canada http://www.phac-aspc.gc.ca/cd-mc/mammography-mammographie-eng.php
References Recommendations on screening for breast cancer in average-risk women aged 40-74 years. CMAJ. 2011 November 22; 183(17):1991-2001. Screening for Breast Cancer: Systematic Evidence Review Update from the U.S. Preventive Services Task Force. Ann Intern Med. 2009 November 17; 151(10):727-W242. http://www.cancer.ca/Canada- wide/About%20cancer/Cancer%20statistics/Stats%20at%20a%20glance/Brea st%20cancer.aspx?sc_lang=en http://www.cancer.gov/cancertopics/types/breast http://www.breastcancer.org/symptoms/types/ Breast Cancer Screening Conversations with Women. PBLP Educational Module. Vol. 20(6), May 2012.
Is the decision to recommend reduced breast screening ethical? “Decisions not to provide certain health-care resources to individuals that seem ethically acceptable at the individual level can also be very contentious” Margaret Somerville founding director of the Centre for Medicine, Ethics and Law at McGill University