Elena Altemus is 89 and has dementia. She often forgets her children’s names, and sometimes can’t recall whether she lives in Maryland or Italy.

Mrs. Altemus, who entered a nursing home in November, was screened for breast cancer this summer. “If the screening is not too invasive, why not?” asked her daughter, Dorothy Altemus. “I want her to have the best quality of life possible.”

But a growing chorus of geriatricians, cancer specialists and health system analysts say that for the best quality of life, she’d be better off skipping the screening. Such testing in the nation’s oldest patients is highly unlikely to detect lethal disease. It is also hugely expensive and more likely to harm than help, since any follow-up testing and treatment is often invasive.

And yet such screening — and the resulting “overdiagnosis” of cancers in people who are unlikely to benefit — is epidemic in the United States, a result of medical culture, aggressive awareness campaigns and financial incentives to doctors.