Do mammograms make sense as an early-warning tool for most seemingly healthy women over age 40? I say yes — with some caveats — to this long and hotly debated question. Others, of course, say no.
Critics of annual mammograms point to the issue of overtreatment. Just last month, for example, a report in the Annals of Internal Medicine showed that screening mammograms (those done for women without signs of breast cancer) often lead to unnecessary treatments. One in three women in the study whose breast cancer was identified by a screening mammogram had a potentially harmless disease that may not require treatment. That work has raised questions about the benefits of screening mammograms.
The findings of screening studies, including mammography, can be influenced by certain biases in the study design.
Length-time bias means that screening is more likely to identify relatively slow-growing cancers which pose less risk to life than more aggressive cancers. This was at play in the Annals study. Lead-time bias means that patients diagnosed through screening, before disease symptoms appear, appear to live longer.
Such biases can come into play in cohort studies, like the Annals report, which follow a large group of women, some of whom chose to have mammograms and others who didn’t. Length-time and lead-time biases can be minimized by randomized clinical trials, in which a large number of women are enrolled. Half of the participants are randomly selected to have screening mammograms, and the other half do not have screening mammograms. A number of such trials have been conducted in the United States and around the world.
Analyses of completed randomized trials have clearly demonstrated a benefit for screening mammograms, with a 15 to 20 percent reduction in breast cancer deaths.
That said, concerns about overtreatment after a suspicious mammogram are valid. The best way to avoid overtreatment of less-aggressive breast cancers is to more accurately characterize the biologic type of every breast cancer. This approach is leading to more appropriate treatment.
For example, we know that breast-conserving surgery (lumpectomy) is just as effective as mastectomy for most women with breast cancer. And recent studies have confirmed that many women with ductal carcinoma in situ, a type of cancer in which the cancerous cells are confined to the lining of the milk ducts and haven’t spread beyond them, do not require radiation after surgery because this type of cancer isn’t very aggressive and poses little risk.
Based on genomic testing studies, we know that there are different molecular subtypes of cancer. One woman’s breast cancer may be quite different from another’s; each type has its own prognosis and requires its own medical treatment.
Many cases of invasive breast cancer are less biologically aggressive than others. The groundbreaking MINDACT study of nearly 6,700 European women with breast cancer showed that genomic testing allowed nearly half of those diagnosed with early-stage invasive breast cancer to safely avoid chemotherapy without compromising their chance of a cure.
Some guidelines recommend that women begin having regular mammograms at age 40, others recommend starting at age 50. Which one is “right” is more an issue about population health than individual health. Adopting what I call “smart screening” may be a better approach. It involves earlier and possibly more intense breast cancer screening among women at higher risk for the disease, perhaps because of their family history, and later and possibly less-intense screening among those at low risk.
When breast cancer is detected, a complete diagnosis must include a review of the cancer’s biology. To make that happen, women diagnosed with breast cancer should see both an oncologist and a surgeon and have their cancer’s genome sequenced before starting any treatment. More than ever, women should feel empowered to take an active role in their treatment by educating themselves, asking questions, and seeking additional medical opinions until they feel comfortable with their path forward.
Treatment options for breast cancer treatment were once determined by the stage of the disease. Today, one-size-fits-all treatment for a particular cancer stage doesn’t work — treatment should be determined first by testing the cancer’s genome to identify its biologic type then by determining the stage of the disease and how much cancer is present.
By combining all of this information, women with early stage breast cancer can get the right treatment and most can confidently expect to be cured of their disease.
Dennis Citrin, MD, is a board-certified medical oncologist at Cancer Treatment Centers of America at Midwestern Regional Medical Center and the author of Knowledge Is Power: What Every Woman Should Know About Breast Cancer.