Modern breast cancer screening is a fairly accurate affair. The Susan G. Komen foundation reports that conventional mammography is 84 percent accurate, meaning that in 84 out of 100 cases, a mammogram film will show a true picture of whether a woman needs additional screening. But what happens to women whose mammograms fall in that other 16 percent, the inaccurate area? They’ll deal with either a false positive or a false negative, neither of which is an ideal situation.
False Positive
In a false positive, a screening test indicates that a mass in the breast is likely to be cancerous. This typically triggers additional imaging such as diagnostic mammograms, which are a bit more involved than a screening mammogram and will help the doctor get a better look at the suspicious growth. You may also be referred for a breast ultrasound or breast MRI. You may even be advised to undergo a breast biopsy — the removal of all or a portion of the suspicious growth for further laboratory testing. All of these tools help doctors get a clearer understanding of what’s going on with your breast health, but each has its own risks and potential complications. Particularly with biopsies, there’s a risk for infection and other complications, so limiting the number of these procedures you undergo is generally advisable.
[See: A Tour of Mammographic Screenings During Your Life.]
Dr. Nikita Shah, medical oncology team leader for the Breast Cancer Specialty Section and medical director of the Cancer Risk Evaluation Program at UF Health Cancer Center — Orlando Health, says “after an abnormal mammogram, the next step is a sonogram, a physical exam and eventually they may need an excisional biopsy” to remove some or all of the growth to analyze it under a microscope. “If it turns out to be nothing, you’ve made the patient go through an unnecessary procedure and anxiety and the cost of all of that.”
In addition to physical risks associated with these tests, women who go through these procedures also endure sometimes intense psychological distress. Being told you may have cancer is a scary ordeal, and some doctors say this stress creates harm. A 2014 study conducted in Denmark found that “having a false positive is not harmless and causes undesirable outcomes in the long run. For a period of three years after being declared free of suspected cancer, women with false positives consistently reported greater negative psychosocial consequences compared with women with normal findings.”
In addition to psychological harms, false positives can also lead to overtreatment in some instances, which in some extreme cases could lead to chemotherapy or radiation therapy when it’s not warranted. A 2015 study published in Population Health Management indicated that the rate of overdiagnosis could be as high as 30 percent. The study notes “current estimates of overdiagnosis in screening mammography vary widely, from 0 percent to upwards of 30 percent of diagnosed cancers. This range reflects the fact that measuring overdiagnosis is not a straightforward calculation, but usually one based on different sets of assumptions and often biased by methodological flaws.” Newer screening technologies such as tomosynthesis, which creates 3D, high resolution images of the breast, are helping reduce the number of false positives, but the technology tends to cost more than traditional mammography and is not as widely available. The report continues: “The greatest harm of overdiagnosis is overtreatment,” and the goal should not be fewer diagnoses, but rather deploying the right tools that will allow for better decisions regarding treatment.
Because of the chances of false positives, several organizations recently changed their screening guidelines for mammograms. Within the past decade, both the U.S. Preventive Services Task Force and the American Cancer Society have both pushed back their recommended starting age for beginning mammograms. This is in part to reduce the number of false positives, but also because younger women tend to have denser breast tissue and conventional mammograms are not as effective in finding cancers in these women. Therefore, these guideline-creating bodies shifted their recommendations for when women should begin annual screenings to 45 or 50 years of age.
Of revising these guidelines, Dr. Kirsten Bibbins-Domingo, chair of the USPSTF, says, “The main message is that mammography is a good tool for women to reduce their chances of dying of breast cancer, but the benefits are more at older ages than at younger. Mammography is more accurate in women between 50 and 74 years old.” She says there can be a benefit to younger women to undergo screening, particularly if they have a strong family history of breast cancer or known genetic mutations, but taken as a whole, the benefit to all women would be “small and must be balanced against potential harms.”
[See: What Not to Say to a Breast Cancer Patient.]
False Negative
On the flip side, sometimes mammograms indicate a woman has no reason to worry about cancer when in fact there’s something there that should be investigated further. Shah says she occasionally sees women in this situation when they come to her later with a more advanced stage of cancer because it wasn’t caught earlier.
In some of these false negative cases, women have “had a mammogram or found a palpable mass and went in for the mammogram, but it was fine. The radiologist said, ‘You’re fine. Come back in six months,’ but when she does, it’s bigger and requires a subsequent biopsy, and it’s cancer. That’s the false negative,” Shah says. And the problem here is that treatment has been delayed six months, a year, two years or possibly longer, and the cancer has had all that time to progress, possibly resulting in a more difficult treatment.
It’s the risk of these situations — and the delay in finding and treating cancer — that causes Dr. Marisa C. Weiss, chief medical officer and founder of Breastcancer.org, a breast cancer education nonprofit, to advocate for women to be vigilant about their breasts and conduct monthly self-exams. When cancers are caught early, “they’re less likely to require drastic treatment. I’ll spare myself chemotherapy,” she says, by being vigilant about her health and pursuing additional diagnostics if something appears abnormal. “There’s a value to early diagnosis for all kinds of cancers,” she says.
Self-Care and Advocacy
Shah says false negatives and false positives happen, and it’s a limitation of the tools we have available to screen for cancer. Nevertheless, there are a few things women can do to help themselves. “Be aware of yourself and your body. If something doesn’t seem right, don’t accept it until you’re sure everything that can be done has been done.” She says some women will get an abnormal reading on a mammogram and fail to follow up on it because they don’t want to think about it. She says that’s never the right answer. “Don’t ignore it. See your health care provider to make sure it’s not significant.”
[See: 7 Innovations in Cancer Therapy.]
She also urges women to seek screening from reputable hospitals and radiology centers. “You don’t want to go to a place where there’s not even a radiologist and the film is being sent abroad to be read. Go to a reputable place or breast care center where you know you’re going to get top-quality care.”
Lastly, she urges women to stay on top of their recommended screening program. “I see so many patients told to go back in three or six months, and they just don’t for whatever reason. There’s a reason why some recommendations are made, and it’s important to follow through with them,” she says.
Breastcancer.org reports that “screening mammograms aren’t perfect,” but they’re “the best way we have right now to detect breast cancer early, when it’s most treatable.” Newer technologies are striving to catch every breast cancer without creating more false positive results, but those technologies have their limitations, too. Until we have a perfect screening tool for all women, false negatives and false positives will continue to be part of the conversation around breast cancer. Taking care of and advocating for yourself is your best means of reducing the chances that you’ll miss a cancer or be overtreated.
More from U.S. News
A Tour of Mammographic Screenings During Your Life
7 Innovations in Cancer Therapy
What Not to Say to a Breast Cancer Patient
False Positives, False Negatives in Breast Cancer originally appeared on usnews.com
