Many doctors have distorted perceptions of the value of medical tests

Editor,

You do your readership and their patients a disservice by implying that physicians who do not adhere to the Canadian Task Force’s guidelines have distorted perceptions of the value of medical tests. Dr. Lang, an emergency physician, and his colleagues on the Task Force are not experts in the fields for which they issue guidelines. They consult experts, but then are free to ignore their input. This was certainly the case with their recent “update” on guideline for breast cancer screening of women at average risk. Though they stated that they had reviewed the most up-to-date data, they did quite the opposite: They considered only randomized controlled trials (RCT) of mammography screening done from the 1960s to the early 1990s, using equipment that is now obsolete. They did not include the 2014 Pan-Canadian observational study of 2.7 million women showing a 40-44% mortality reduction among screened women.

Randomized trial design works well for drug trials. In a technology-dependent study, by the time the study has matured to the point that mortality reduction can be measured, the technology has advanced, and that used in the trial is no longer in use. The RCTs of mammography used x-ray film mammography. This has been replaced with digital mammography, which is more sensitive at cancer detection.

Furthermore, RCTs only demonstrate mortality reduction. Early detection of breast cancer allows 3 other important benefits NOT considered by the Task Force: the possibility to avoid mastectomy, axillary dissection and lymphedema, and even chemotherapy.

A growing body of evidence shows that women with dense breasts are at increased risk in 2 ways: They are at increased risk of developing breast cancer (women with the densest of the 4 categories are 4-6 times higher risk than women with the lowest category; a greater risk than having a mother or sister with breast cancer), and the missing of cancer on mammograms by normal breast tissue.(1-5) Mammography is 96% sensitive in fatty breast, but misses 50% of cancers in extremely dense breasts.(6) These undetected cancers grow, and potentially metastasize until they are eventually detected when they or the metastatic nodes become palpable. These are called interval cancers, and have a worse prognosis than screen-detected cancers, in spite of modern therapies.(7-10)

The recent Task Force Guideline considers women with dense breasts to be at average risk, and holds that there is insufficient evidence to recommend supplementary screening for women with dense breasts. Indeed, observational studies show that screening ultrasound in these women detects 3-4 small invasive, node-negative cancers per thousand women, and reduces interval cancers.(11-13) A RCT is underway in Japan,(13) but women with dense breasts should not have to die, and young families lose their wives and mothers, until it matures.

The Task Force receives funding from the Federal Ministry of Health. Happily, physicians for the most part do not blindly follow their guidelines. The danger is that the guidelines can/do act as a default for provincial screening programs. In my opinion physicians should do what is best for their patients and ignore the Task Force’s breast cancer screening guidelines for women at average risk, and likely many other of their guidelines.

References

1. Engmann NJ et al. Population-Attributable Risk Proportion of Clinical Risk Factors for Breast Cancer. JAMA Oncology 2017;3: 1228-1236.

2. Carney PA, Miglioretti DL, Yankaskas BC, et al. Individual and combined effects of age, breast density, and hormone replace- ment therapy use on the accuracy of screening mammography. Ann Intern Med 2003;138(3):168–175.

3. Kerlikowske K, Hubbard RA, Miglioretti DL, et al. Compara- tive effectiveness of digital versus lm-screen mammography in community practice in the United States: a cohort study. Ann Intern Med 2011;155(8):493–502.

4. Boyd NF, Martin LJ, Yaffe MJ, Minkin S. Mammographic density and breast cancer risk: current understanding and future prospects. Breast Cancer Res 2011;13(6):223.

5. McCormack VA, dos Santos Silva I. Breast density and paren- chymal patterns as markers of breast cancer risk: a meta-analysis. Cancer Epidemiol Biomarkers Prev 2006;15(6):1159–1169.

6. Kolb T.M., Lichy J., Newhouse J.H. Comparison of the performance of screening mammography, physical examination, and breast US and evaluation of factors that influence them: An analysis of 27,825 patient evaluations. Radiology. 2002;225:165–175.

7. Boyd NF et al. Mammographic density and breast cancer risk: current understanding and future prospects. Breast Cancer Res 2011; 13:223

8. Pisano ED et al. Diagnostic Performance of Digital versus Film Mammography for Breast-Cancer Screening. NEJM 2005; 353:1773–1783

9. Boyd NF et al. Mammographic Density and the Risk and Detection of Breast Cancer. NEJM 2007; 356:227–236

10. Yaghjyan L et al. Mammographic Breast Density and Subsequent Risk of Breast Cancer in Postmenopausal Women According to Tumor Characteristics. JNCI 2011; 103:1179–1189

11. Berg WA, et al. Detection of breast cancer with addition of annual screening ultrasound or a single screening MRI to mammography in women with elevated breast cancer risk. JAMA 2012; 307:1394-1404

12. Weigert J.The Connecticut Experiment; The Third Installment: 4 Years of Screening Women with Dense Breasts with Bilateral Ultrasound.
Breast J 2016;1-6

13. Ohuchi N. Sensitivity and specificity of mammography and adjunctive ultrasonography to screen for breast cancer in the Japan Strategic Anti-cancer Randomized Trial (J-START): a randomised controlled trial. The Lancet 2015; 387:341-348