A radiology group at an Arizona hospital recently missed obvious breast cancer in dozens of women’s screenings, delaying their diagnosis. These misread scannings are frightening and can have fatal consequences, and what’s just as scary is that 1 in 5 breast cancers aren’t diagnosed during routine screens for the two-thirds of women over the age of 40 in the U.S. who do get a regular mammogram. These are interval breast cancers that are hard to find or might not have been present at the time of a routine exam. Most often, interval breast cancers appear after a woman had a normal mammogram result, but before her next routine mammogram.
Interval breast cancer is putting millions of women at risk of a potentially fatal delay in diagnosis. Public awareness about how to spot interval breast cancer, even when it’s missed by a mammography machine could save their lives.
Interval breast cancers are typically more aggressive and lethal than screen-detected cancers. Interval cases have two to three times higher risk of death from breast cancer compared with cancers found during a routine mammogram.
Interval breast cancers are often larger in size, have more lymph node involvement, and are of a higher grade and later stage than cancers found during routine mammography.
Only about 20-25% of interval breast cancers are missed cancers. Most interval breast cancers are true cancers that are new cancers or that were not present at the last mammogram.
Lobular cancers are harder for mammograms to see because they may spread in lines and may not have visible calcifications like other breast cancers.
Mammography machines could also miss breast cancers in women with dense breasts. Dense breasts increase the risk of breast cancer, but also mask tumors and make them harder for the machine to see the tumor.
Women with interval breast cancer usually notice something wrong through a breast self-exam or by accident when getting dressed or showering. Symptoms vary from woman to woman, but most common symptoms are a lump and skin or nipple changes. Other noticeable symptoms include a cyst, pain or burning sensation, nipple discharge or breasts that look abnormal.
Even after noticing symptoms, many women wait to reach out to their doctor because they recently had a mammogram with normal results. Some women hesitate to have their symptoms checked because they do not want to appear foolish or may have concerns about not being heard or medical gaslighting. But waiting may allow the tumor to grow larger.
As an author in a 2020 cohort study comparing mortality and characteristics of interval and screen-detected cancers, interval breast cancer tumors were almost half a centimeter larger for those diagnosed with a routine mammogram. For most breast cancer, as tumor sizes increase, the chance for metastases also increases.
Women should check their breasts monthly. If there are any symptoms, calling the doctor to schedule a visit should happen immediately. Sooner is always better to start treatment. Reaching out to a primary care doctor or their gynecologist is most common, but the best route is to call any trusted health care provider they feel most comfortable with. Women with symptoms and no regular source of care should go to urgent care.
Physicians and other medical professionals can also support women without insurance coverage by directing them toward resources that focus on breast health. The Affordable Care Act (ACA) does require that new plans cover mammograms for screening. However, the ACA doesn’t require that all plans cover mammograms for diagnostic purposes – meaning when women come in with symptoms. When insurance plans don’t cover diagnostic services, the Centers for Disease Control and Prevention’s National Breast and Cervical Cancer Early Detection Program can find options based on the region. Non-profits organizations such as the Pink Lemonade Project, the Susan G. Komen and American Cancer Society can assist with stipends or covering prescriptions or other services.