– Surgery is a mainstay of breast cancer treatment, offering most women a good chance of cure.

For frail nursing home residents, however, breast cancer surgery can harm their health and even hasten death, according to a study published this week in JAMA Surgery.

The results have led some experts to question why patients who are fragile and advanced in years are screened for breast cancer, let alone given aggressive treatment.

The study examined the records of nearly 6,000 nursing home residents who had inpatient breast cancer surgery in the past decade. It found that 31 to 42 percent died within a year of the procedure. That’s significantly higher than the 25 percent of nursing home residents who die in a typical year, said Dr. Victoria Tang, lead author and an assistant professor of geriatrics and hospital medicine at the University of California, San Francisco.

Although her study doesn’t include information about the cause of death, Tang said she suspects that many of the women died of underlying health problems or complications related to surgery, which can further weaken older patients. Patients who were the least able to take care of themselves before surgery were the most likely to die within the following year.

Dementia also increased the risk of death. Yet nearly 1 in 5 women with severe cognitive impairment get regular mammograms, said a study in the American Journal of Public Health.

It’s unlikely that many of the deaths were because of breast cancer, which often grows slowly in the elderly, Tang said. Breast cancers often take a decade to turn fatal.

“When someone gets breast cancer in a nursing home, it’s very unlikely to kill them,” said study co-author Dr. Laura Esserman, director of the UCSF breast cancer center. “They are more likely to die from their underlying condition.”

Yet most patients in the study got sicker and less independent in the year after breast surgery. Among patients who survived at least one year, 58 percent suffered a serious downturn in their ability to perform “activities of daily living,” such as dressing, bathing, eating, using the bathroom or walking across the room.

Women in the study, who were on average 82 years old, suffered from a variety of life-threatening health problems even before their breast cancer was diagnosed. About 57 percent suffered from cognitive decline, 36 percent had diabetes, 22 percent had heart failure, 17 percent had chronic lung disease and 12 percent had survived a heart attack.

The high mortality rate in the study is striking because breast surgery is typically considered a low-risk procedure, said Dr. Deborah Korenstein, chief of general internal medicine at New York’s Memorial Sloan Kettering Cancer Center.