What’s the best way to screen for breast cancer? Opinions differ.

By ThinkReliability Staff

In 2015, there were 40,000 deaths from breast cancer and 232,000 new cases of breast cancer in the United States. It is the second-leading cause of cancer death in women in the United States. The very high level cause-and-effect is that people (primarily women) die from breast cancer due to ineffective treatment. The later the cancer is detected, the later the treatment begins so early detection can help prevent breast cancer deaths. Currently the best solution for detecting breast cancer is a mammogram. But the matter of when mammograms should occur is based on risk-benefit analysis.

There’s no question that mammograms save lives by detecting breast cancer. This is the benefit provided in the analysis. Lesser known are the risks of mammograms. Risks include false negatives, false positives, unnecessary biopsies, and unnecessary treatment. The radiation that may be used in treatment can actually be a cause of future breast (and other types) of cancer.

On January 11, 2016, the United States Preventive Services Task Force (USPSTF) issued an update of their guidelines on mammogram starting and ending age (as well as other related recommendations). To develop these recommendations, the task force attempted to quantify the risks and benefits of receiving mammograms at varying ages.

For women aged 40 to 49, the task force found that “there is at least moderate certainly that the net benefit is small.” The net benefit here reflects the benefits of screening (~.4 cancer deaths prevented for every 1,000 screened and an overall reduction in the risk of dying from breast cancer from ~2.7% to ~1.8%) compared to the risks of screening. Risks of mammograms every other year for women aged 40 to 49 include ~121 false positives, ~200 unnecessary biopsies, ~20 harmless cancers treated, and ~1 false negative for every 1,000 women screened. The task force determined that in this case, the benefits do not significantly outweigh the risks for the average woman. Thus, the recommendation was rated as a C, meaning “The USPSTF recommends selectively offering or providing this service to individual patients based on professional judgment and patient preferences.” (Women who are at high risk or who feel that in their individual case, the benefits outweigh the risk, may still want to get screened before age 50.)

For women aged 50 to 74, the task force found that “there is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial.” The types of benefits and risks are the same as for screening women ages 40 to 49, but the benefits are greater, and the risks are less. For women aged 50 to 74, there are ~4.2 cancer deaths prevented for every 1,000 screened and an overall reduction in the risk of dying from breast cancer from 2.7% to ~1.8%.   Risks of mammograms every other year for women aged 50 to 74 include ~87 false positives, ~160 unnecessary biopsies, ~18 harmless cancers treated, and ~1.2 false negatives for every 1,000 women screened. The task force determined that for women aged 50 to 74, the benefits of mammograms every other year outweighs the risk. Thus, the recommendation was rated as a B (the USPSTF recommends the service).

The task force determined it did not have enough evidence to provide a recommendation either way for screening women over age 74.

Comparing these risks to benefits is a subjective analysis, and some do not agree with the findings. Says Dr. Clifford A. Hudis, the chief of breast cancer medicine at Memorial Sloan Kettering Cancer Center, “The harm of a missed curable cancer is something profound. The harm of an unnecessary biopsy seems somewhat less to me.” To those that disagree, the task force reiterates that personal preference should determine the age screening begins. However, insurers may choose to base coverage on these recommendations. (Currently, private insurers are required to pay for mammograms for women 40 and over through 2017.)

Determining these recommendations – like performing any risk-benefit analysis – was no easy task and demonstrates the difficulty of evaluating risks vs. benefits. Because these analyses are subjective, results may vary. To view the risk vs. benefit comparison overview by the task force, click on “Download PDF” above.