By Jennifer Kearney-Strouse
Reconciling guidelines on breast cancer screening can be difficult, according to Alexandra S. Heerdt, MD, MPH.
"I think this is what we all struggle with on a regular basis," she said. "You can get many different guidelines, and it's hard to decide what is appropriate for any given person." At a Thursday session, "Clinical Triad: Cancer Screening Updates and Controversies," she offered advice on weighing risks and benefits of mammography to help patients make screening decisions.
Pain associated with the mammography procedure is often a concern for women, said Dr. Heerdt, who is a breast surgeon at Memorial Sloan Kettering Cancer Center in New York City. However, no studies have followed women who reported mammography pain to see if it persisted over the longer term. "We presume it doesn't, although there are some women who never go back after their first mammogram, and you don't know if it's because of that," Dr. Heerdt said.
She noted that patients have reported initially increased anxiety about current and future cancer risk associated even with a routine mammogram, especially if false-positives lead to additional tests, citing a systematic review published in Health Technology Assessment in 2013.
"When asked later on after additional imaging, the good news is that 98% of those women would say that it was all worth it, and there's no evidence that these women go on to have long-term anxiety from these additional examinations," Dr. Heerdt said. "So, while I think this is an important thing to consider when talking to your patients, I think that we also have to recognize that this is a short-term anxiety for the majority of women."
Radiation exposure is another concern, but Dr. Heerdt pointed to a study published in Medical Physics in 2010 looking at the amount of radiation exposure with mammography at different ages and frequencies. Radiation induces 56 additional cancers per every 100,000 patients screened between ages 40 and 80 years, and 35 of those are due to screening between the age of 40 and 49 years, she said.
While that's a number to keep in mind when considering screening women in their 40s, the life-years gained and mortality reduction in that age group may offset it significantly, she noted. "We have to take it into account, but I'm not sure it's as great as we might think it is," she said.
False-positive results are "the crux of the issue" with concerns about overdiagnosis and overtreatment, Dr. Heerdt said. She described a study done with SEER data from Connecticut and published in the New England Journal of Medicine in 1998, which found that 6% of mammograms with false-positive results led to some form of biopsy.
"Over the period of this study, which was a 10-year period, almost 25% of women actually ended up needing to have either additional imaging or a biopsy, so it is not insignificant. A quarter of the population," she said.
The study also found that women ages 40 to 49 years had a slightly higher chance of having a false-positive mammogram than average, while those ages 70 to 79 years had a less than 5% chance. "Interestingly, though, it's not that different between 40 to 49 and 50 to 59, so again, thinking about where to make the cutoffs, you have to think about those types of things as well," Dr. Heerdt said. She also reviewed data on false-positive rates from the U.S. Preventive Services Task Force published in Annals of Internal Medicine in 2016 and noted that while more false-positives are found in patients ages 40 to 49 years, fewer breast biopsies are done in this group. "And again, the false-negative rate is not as significant as you might think it is," she said.
On the benefits side, Dr. Heerdt pointed to a study published in Cancer in 2014, which found that cancer stage at diagnosis decreased over time as use of mammography increased. While rates of ductal carcinoma in situ increased by 800%, diagnoses of localized disease, stage 1 disease, and early stage 2 disease also increased by 70% between the 1970s and the early 1990s. Another study, a systematic review published in the European Journal of Cancer in 2020, found that organized screening reduced breast cancer mortality in all European regions where it was implemented and monitored.
"And we have to remember that these trials were all done in a period when mammography was not nearly as good as it is today. We would hope that it would be a better production at this point," Dr. Heerdt said.
Regarding when screening should end, Dr. Heerdt referred to 2022 SEER data from the National Cancer Institute. "This is newer data, and I think it's important to look at it," she said. The numbers indicate that while only 20% of breast cancers occur in women over the age of 75, as many as 40% of those women die of the disease. "While the life-years gained [with mammography] are not great, there is mortality associated," Dr. Heerdt said. "So we do have to revisit when our ending is, and I think that's an area that is open for research." ■