Shifting Guidelines in Screening for Breast Cancer and Cervical Cancer

November 30, 2009

Recently, two groups released new guidelines that may affect breast cancer and cervical screening in women.

Recently, two groups released new guidelines that may affect breast cancer and cervical screening in women. The US Preventive Services Task Force (USPSTF) recommended against screening women in their 40s and to screen women every other year starting at age 50. The USPSTF left room for individualized screening, particularly in the presence of risk factors such as family history. Still, it is a departure from previous recommendations (and current standard) for annual screening of women starting in their 40s. For cervical cytology screening, the American College of Obstetricians and Gynecologists (ACOG) revised its pap smear guidelines, calling for women to receive them every two years between the ages of 21 and 30. The revised recommendations say that women age 30 and older who receive three consecutively negative test results may be screened once every three years. This, too, is a departure, as previous guidelines recommended annual cervical cytology screening beginning three years after the onset of sexual activity. Both revised guidelines have ignited a firestorm of controversy, though the response to the cervical cancer screening guidelines has been less severe.

I do not believe the controversy stems from the actual recommendations being made. In both guidelines, a panel of experts reviewed the latest information before recommending changes. What is interesting is how the data were actually used. In the mammography guidelines, the data were used to generate mathematical models of benefits and harms for screening. Using these models, the reviewers determined that 1,900 women between the ages of 40 and 49 would be invited to be screened to save one woman from breast cancer. Still, the benefit was statistically significant, as noted in the relative risk of 0.85 (CI, 0.75 to 0.96). The fact that relative risk does not cross 1 makes it so. So, here we have a statistically significant finding, which the USPSTF takes as non-clinically significant. But then, how much is a life worth?

The ACOG recommendations were data-driven as well, but pooled from the evidence. No modeling was performed. Instead, the biology and natural history of HPV and of cervical cancer were taken in to account, coupled with the long-term consequences of intervening early in a woman's life. The fact that invasive cervical cancer represents a step-wise progression from abnormal changes in the cervix (which all can be picked up with cervical screening) makes cervical cancer a rare disease in women under age 21 and explains why three consecutively negative pap smears does not necessitate continued annual testing.

Still, there is another difference. ACOG recommendations represent those of the group that is doing the pap smears, interpreting them for their patients, acting on the abnormal results, and then seeing the consequences of their intervention. The USPSTF cannot be clearly deemed to be the same. These are not oncologists, surgeons, and/or breast imagers. Instead, the USPSTF is composed of medical experts in primary care. They are not breast specialists by any measure, so their recommendations of what constitutes "unreasonable risks" are bound to be controversial, particularly when the risk women are most alarmed about is "death from breast cancer.”