By Lisa Rapaport
(Reuters Health) - Screening mammograms don't benefit women aged 75 and older with chronic health problems - such as heart disease or diabetes - that are likely to end their lives before they develop cancer, a new study suggests.
Researchers examined data on 222,088 women who had at least one screening mammogram between 1999 and 2010 when they were between 66 and 94 years old. Researchers followed most women for nine years or more.
During the study, 7,583 women, or about 3%, were diagnosed with invasive breast cancer and 1,742 women, less than 1%, were diagnosed with pre-invasive malignancies known as ductal carcinoma in situ (DCIS). While 471 women died of breast cancer during the study, 42,229 died of other causes.
This means women were 90 times more likely to die of causes other than breast cancer, researchers report in the Journal of the National Cancer Institute.
"Having more chronic illnesses increases the risk of dying from non-breast cancer causes, while having no impact on the risk of breast cancer or breast cancer death," said Dejana Braithwaite, senior author of the study and a researcher at Lombardi Comprehensive Cancer Center at Georgetown University in Washington, D.C.
"This is a big deal because, while younger women might have a more justifiable reason to undergo screening mammograms to detect breast cancer because their risk of dying from other causes is relatively low, this is not the case in older women, particularly those with one or more chronic illnesses," Braithwaite said by email.
Women ages 75 to 84 were 123 times more likely to die of causes other than breast cancer; this estimate was even higher among women age 85 and older.
The 10-year risk of dying from breast cancer was small and did not vary by age; it stayed about the same from age 66 to 94, accounting for just 0.2% -0.3% of all deaths in the study.
By contrast, the risk of dying from other causes increased with age and also climbed with each additional chronic medical problem a woman had.
The goal of screening mammography is to detect tumors before they can be felt in a physical breast exam, catching cancer sooner when it's easier to treat. Ideally, this should mean fewer women are diagnosed when tumors are bigger, rapidly growing and harder to attack.
But some research suggests that screening too early or too often can also catch more small, slow-growing tumors that are unlikely to be fatal - without curbing the diagnosis of advanced cancer cases. Harms of too much screening can include unnecessary invasive follow-up tests and cancer treatments for tumors that never would have made women sick or led to their death.
The United States Preventive Services Task Force notes that there is not enough evidence to recommend for or against screening women age 75 or older. Many breast cancer programs in Europe stop screening women between the ages of 69 and 74.
In the U.S., despite these recommendations, many women in their 80s and 90s still get screening mammograms, the study team notes.
One limitation of the analysis is that it only included women who continued to get screening mammograms as they aged, and it's possible results for all women in the population, including those who stopped getting mammograms, might be different, researchers note.
"Our study included large numbers of older women unlikely to benefit from screening mammography," Braithwaite said. "Women ages 75 and older with chronic illnesses are unlikely to benefit from continuing mammograms, however, these findings underscore the need for more individualized screening strategies, rather than making sweeping recommendations."
SOURCE: https://bit.ly/2kcRguy Journal of the National Cancer Institute, online September 6, 2019.