New breast exam guidelines are confusing, counterintuitive

Recent changes to the American Cancer Society guidelines on screening and early detection of breast cancer are confusing and contradictory. Oddly, the screening methods that are easiest and least expensive are not recommended. The ACS recommends that women between 45 and 54 who are at average risk for cancer and have no symptoms get annual mammograms and that women age between 40 and 45 should be able to have them if they choose. After 55, women can choose to have them every two years as long as they are otherwise healthy and can expect to live at least ten years.

The U.S. Preventive Services Task Force (USPSTF) recommends less frequent mammograms. The organization is in the process of updating its 2009 guidelines, but major changes are not expected.

Are routine mammograms helpful?

Mammography has been promoted as a life-saving procedure in that it leads to early detection, and cancer is more treatable and curable when detected early. But there also is evidence that mammography leads to false positive results. The image may reveal an anomaly, such as a small mass, requiring the woman to be called back for additional screening or a biopsy. The call-back alone can be anxiety-producing; even if the test reveals cancer, the mammogram may not save her life. It may be that the cancer is so small, and so localized, that there is little or no risk to life. But once the doctor finds cancer, the next step is likely to be treatment.

A 2012 study published in the New England Journal of Medicine examined the relationship between the rising use of mammograms to detect breast cancer and the frequency of breast cancer deaths. As exposure to mammograms rose, beginning in the mid-1970s, there were more diagnoses of early-stage cancer.

When the study began, it was commonly recommended that women begin to have regular screening mammograms at age 40. Screening mammograms, to check for disease in the absence of any symptoms, were not recommended for women under 40 unless they were at higher-than-usual risk. As mammography technology improved, the number of early-stage cancers found also grew. But the number of invasive cancers found did not drop as much as the number of early cases grew. The investigators concluded that a significant portion of the cancers detected by mammograms would never have progressed to late-stage, life-threatening cancer.

Although the number of deaths from breast cancer dropped significantly, the investigators could not attribute the drop to early detection through mammography. The rate of breast cancer deaths in women over 40 dropped 28 percent during the three decades covered by the study. The death rate among women under 40, the group who did not undergo screening mammograms, dropped 42 percent during the same period. Moreover, the frequency of patients presenting with late-stage cancer, which had spread beyond the breasts, remained relatively constant. The investigators concluded that other factors, particularly improvements in treatment, had more impact on breast cancer deaths than screening mammograms.

The Preventive Services Task Force grades

The United States Preventive Services Task Force (PSTF) uses letter grades to rate the relative benefits of preventive services. Its 2009 guidelines gave a B grade to screening mammograms every two years for women between the ages of 50 and 74; the 2015 draft guidelines make no change to this recommendation. The B grade means that there is a “good chance of moderate to substantial benefit” to women who follow the guidelines; women between the ages of 60 and 69 are most likely to avoid death from breast cancer through screening mammograms.

The controversy concerns the recommendation for women between the ages of 40 and 49. The PSTF gave biannual mammograms a grade of C for this age group, meaning that there is “moderate certainty of a small net benefit” for women at average risk. A small number of cancer cases would be caught, and a larger number of women would be treated unnecessarily. Women who have a parent, child or sibling with a history of the disease are more likely to benefit.

Clinical and self-examination

The PSTF gives  a grade of D to teaching women BSE and a grade of I to clinical examination of the breast (CBE) by a physician during exams. The D grade means “there is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits.” Therefore, the use of the service is discouraged.  Still, the National Cancer Institute and the ACS recommend that women be familiar with how their breasts look and feel and report any changes to their physician. The clinical examination was given a grade of I, meaning that there is insufficient evidence to determine the extent of benefit or harm. The “clinical considerations” discussion stated that CBE may detect a significant portion of breast cancers if it is the only screening test available, as in parts of the world where mammography is unavailable.  But the disadvantage is that apparently there is no standard method either to perform the examination or to report the results. And aside from the danger of false positives, there is the “opportunity cost” to the clinician. So the PSTF recommends that clinicians who are “committed to spending time on CBE would benefit their patients by considering the evidence of a structured, standardized examination.”

Actually, a structured, standardized examination is exactly what women were taught to do. And there is  evidence that it can catch some cancers that arise between mammograms. So why wouldn’t physicians want to learn to perform a proper exam?