Last week’s controversy over the new U.S. Preventive Services Task Force (USPSTF) recommendations on breast cancer screening inevitably presages more such decisions to come. Whether or not health care reform legislation is enacted, unavoidably we will confront many more such decisions and their difficult benefit-risk-cost trade-offs about what services should be provided. The debate over the USPSTF’s mammography recommendations indicates that we have a long way to go in rationally working through these issues.

The new guidelines recommend against routine mammograms for women under the age of 50, and they dial back the recommended frequency of screening for women ages 50–74 from once every year to once every two years. USPSTF reasoned that while the old guidelines saved lives, the marginal benefit of screening before age 50 and of screening more often after age 50 were small compared to the harms, including the psychological impact of unnecessary imaging, false positives, and invasive procedures to address identified cancers that may never have become clinically apparent.

The American Cancer Society similarly weighed the benefits and risks of screening but came to a different conclusion. The cancer society noted that “like the USPSTF, the American Cancer Society panel also found that mammography has limitations – some women who are screened will have false alarms; some cancers will be missed; and some women will undergo unnecessary treatment. These limitations are somewhat greater in women in their forties compared with women in their fifties…” But unlike the USPSTF, the cancer society concluded that even for women between the ages of 40 and 49, “the lifesaving benefits of screening outweigh any potential harms.”

Will further debate lead to consensus? The two sides seem to agree about the state of the science, and both claim they compared the benefits and harms of screening. Nonetheless, it appears one element is largely missing from both sides – namely a clear statement of how they weighed benefits and harms.

USPSTF explains 1,904 women ages 40–49 must be screened to extend one woman’s life. For women in their 50s, the corresponding figure is 1,339 women. Given these results, it seems that the cancer society is reasonable in asking why the USPSTF drew a line at age 50. Yes, women in their 40s gain less risk reduction from screening, but only one-third less than women in their 50s. Is that difference enough to flip a positive benefit for women in their 50s to a negative benefit for women in their 40s?

The American Cancer Society can be faulted for the same omission. It argues that the benefits of routine screening for women in their 40s outweigh the harms. But where does it draw its line? Screening women in their 30s, or conducting screening semi-annually rather than annually, may save even more lives than are saved by the guidelines supported by the cancer society. Would the cancer society advocate for more screening, or at least for clinical trials to empirically evaluate more intensive screening guidelines?

It is admittedly difficult to identify the balance point between false positive test results and lives extended through mammography. The USPSTF and the cancer society have done so implicitly – USPSTF believes approximately 1,900 false positives per life extended is too many, while the cancer society believes that at least that many is a price worth paying.

The problem is that neither side has made this point explicitly. As a result, the real source of disagreement – where to draw that line – is never argued openly. There is no guarantee that an open debate about where the line should be would generate consensus. But at least the public, health care providers, and patients would better understand why the two sides disagree. Without that understanding, the positions taken by USPSTF and cancer society can seem arbitrary, or driven by unstated motives, something that damages the credibility of this type of analysis.

If this reluctance is representative of how we deal with other trade-offs in health care, it does not bode well for our handling of countless other decisions our country faces going forward. Inevitably, other decisions will involve trade-offs between clinical benefits and risks. Even more complicated will be risks and benefits that accrue to different subgroups in the population (for example, if a flu vaccine is in short supply, which subpopulations should have priority?).

Of course, economic costs are another type of trade-off we cannot avoid. Without acknowledging this truth, and without an open discussion about how much we are willing to spend to achieve therapeutic benefits, consistent and fair allocation of health care resources is unlikely.

Some members of Congress have decried the USPSTF recommendation as an example of the type of rationing we will face with more government involvement in health care. But the USPSTF did not create the trade-off between the risks and benefits of screening; they only highlighted it. Because resources to spend on health care are finite, failing to analyze these trade-offs will not make them go away either.

If we are to deal with those trade-offs, we will have to go even further than the USPSTF and American Cancer Society have gone. We must be willing both to lay the facts on the table and to be open and honest about what tradeoffs we are willing to make.

Joshua T. Cohen, Ph.D, is a research associate professor of medicine and deputy director of the Center for the Evaluation of Value and Risk in Health, within the Institute for Clinical Research and Health Policy Studies at Tufts Medical Center. jcohen@​tuftsmedicalcenter.​org; 617–636-8280. Peter J. Neumann, Sc.D, is director of the center and a professor of medicine. pneumann@​tuftsmedicalcenter.​org. 617–636-2335.