Guidelines and Risk-Based Screening
By convention, in the United States, most guidelines for breast cancer screening recommend that women begin screening at age 40 or at some time in their 40s. Guidelines that recommend screening beginning at age 50 are based more on previous debates over efficacy of screening before age 50 than on disease burden. The age of 40 is admittedly arbitrary and based on the legacy of methodologic decisions related to choosing study populations for the trials. Shapiro and colleagues included women age 40 and older after they observed that more than one-third of the premature mortality from breast cancer occurred in women diagnosed between the ages of 40 and 49.
Since 1997, the ACS, NCI, and ACR have released updated guidelines for breast cancer screening, in large part informed by new data published in 1997. Each organization recommends that women begin regular screening mammography in their 40s. The United States Preventive Services Task Force currently recommends mammography every 1 to 2 years for women beginning at age 50, having concluded that there is insufficient evidence to recommend for or against breast cancer screening before the age of 50. However, their last guidelines update was published in 1996, before the availability of more recent individual trial and meta-analysis findings. NCI recommendations differ from those of the ACS and ACR by not specifying a specific age to begin screening.
The NCI guidelines also recommend screening at intervals of 1 to 2 years versus annual screening and encourage women at higher risk to consult with their physicians about establishing an interval for periodic screening that is appropriate in their individual case. Current differences in breast cancer screening guidelines are a function of the timing of evidence-based literature reviews and different approaches to evidence-based medicine.
Some have questioned the value of screening women older than age 70, based on both lack of evidence from randomized trials (only one trial included women over the age of 70) and lower cost-effectiveness. On the issue of a lack of data, the U.S. Preventive Services Task Force found little evidence to conclude that breast cancer screening would be any less beneficial in women older than age 70.
Further, although comorbidity increases with increasing age, a significant percentage (71%) of the population older than age 65 rate their health as excellent, very good, or good. Given the high breast cancer incidence and mortality among women older than age 65, it is a mistake to presume that screening is not beneficial to this group. The ACS has asserted that there is no upper age limit for screening mammography, and as a general rule as long as a woman is in reasonably good health and does not have such significant comorbidity that she would not be a candidate for surgery, screening is recommended.
Whereas some organizations recommend breast self-examination (BSE) and CBE in their guidelines, others do not, mostly because of the lack of clear evidence of their efficacy as a stand-alone examination or in combination with mammography. Randomized trials of screening have shown mortality reductions among women invited to screening that included either mammography or mammography in combination with CBE. In the HIP study and the BCDDP, CBE was responsible for finding some cancers not detected by mammography.
However, it is unclear what CBE contributes to breast cancer detection apart from mammography, although few would question the value of CBE as a complementary modality. Some breast cancers cannot be seen on a mammogram, or the mammographic examination may be enhanced if there is awareness of a palpable mass detected by CBE. For this reason, the ACS has recommended that CBE should occur close to and before the occasion of a screening mammogram. Furthermore, recommendations from the AHCPR’s Quality Determinants of Mammography strongly assert that a negative mammogram in the presence of a palpable mass does not rule out breast cancer. It should be stressed, however, that the value of CBE is determined by the quality of the examination.