In response to the Canadian National Breast Screening Study update, published in the British Medical Journal, the American Society of Clinical Oncology (ASCO) emphasizes the following:
There has been a longstanding debate over the most appropriate age and frequency of mammography screening for breast cancer. This report is a reanalysis of a previously reported study that now provides longer-term follow-up. The study reaffirms earlier results showing no reduction in mortality in women age 40-59 who were screened with mammography compared with those who did not receive mammography screening. Importantly, the updated report provides a more reliable estimate of the risk of overdiagnosis associated with routine mammography screening. Mammography is similar to many other screening tests in that it can detect some tumors that would never have caused problems for the patient had they not been detected (overdiagnosis). It is also known that women who are not at an elevated risk for cancer have a greater potential for harm from screening due to an increased risk of a false-positive result (a positive test result that turns out not be to be cancer). However, the benefits of screening are likely to be greater for women who are at increased risk of developing breast cancer based on factors such as age and family history, than for women at average risk.
Although this is a large randomized trial, no single study should be used to change screening policy. ASCO therefore encourages all women to speak with their doctors about their personal risk for breast cancer starting at age 40, or even earlier in some situations, as well as the potential benefits and harms of mammography screening. Together they should decide whether mammography screening is appropriate. A woman’s personal decision regarding mammography screening should be based on her own individual risk for breast cancer, and determined by weighing the risks and benefits of screening.
ASCO feels strongly that there should be no overall policy change. Furthermore, after considering the potential risks and benefits of mammography screening, women who choose to undergo the test should not face any impediments to doing so.
The Society will continue to monitor and analyze new data on mammography screening as it emerges.