Researchers found that among women who had been diagnosed with a certain type of breast cancer, those over 75 years old were 63 percent more likely to die of the cancer than women younger than 65.

"I suspect it's undertreatment," said Dr. Stephen Jones, one of the authors of the study and the medical director at US Oncology Research in Texas. "We did show the rates of chemotherapy and radiation therapy are less in the older group."

Jones and his colleagues tracked nearly 10,000 women who had already gone through menopause and who had been diagnosed with hormone receptor-positive breast cancer.

That is the most common type of the disease, and it is considered less dangerous than the hormone receptor-negative types because it is often slower growing and might respond to hormone treatments.

Younger women are more likely than older women to have the receptor-negative cancer and they also tend to get diagnosed at a later stage, leading to the idea that breast cancer is more deadly for them.

In this study, the researchers found that five out of every 100 women who were diagnosed under age 65 and six out of every 100 women diagnosed between 65 and 74 years old died from breast cancer within five years.

Among women over age 75 at the time of their diagnosis, eight out of every 100 died from the cancer.

The team isn't sure how to account for the gap, but Dr. Hyman Muss of the University of North Carolina School of Medicine, agreed with Jones.

"What's different in older women is they tend to get lesser and poorer treatment," said Muss, who was not involved in the new study.

About one in eight American women will get breast cancer at some point in their life, but less than a fourth of them will die from it.

Breast cancer can be treated with a combination of surgery, radiation, chemotherapy and hormonal medications.

Nearly all the women in the study went through surgery, but just half of the women over age 75 had radiation, and just five percent had chemotherapy.

In comparison, 75 percent of women under age 65 received radiation and 51 percent had chemotherapy.

"There are beliefs that older women do not benefit from chemotherapy as much as younger women, and that the side effects are worse," said Dr. Gerrit-Jan Liefers, a researcher at Leiden University Medical Centre in The Netherlands who also worked on the study.

He added that the patients themselves may also be more hesitant to treat their cancer aggressively.

A recent study found that, while the rates of breast cancer deaths have been slowing, older women have had smaller gains than younger women (see Reuters Health report of November 11, 2011).

Those authors also attribute the differences in part to less aggressive treatment in older women.

"You don't want to treat older women so aggressively that you actually cause more problems from the treatment than from the disease," Dr. Benjamin Smith from the University of Texas MD Anderson Cancer Center in Houston, who worked on that study, told Reuters Health in November.

Muss said it's possible to overtreat elderly patients, but otherwise healthy women in their 70s would likely benefit from chemotherapy.

"We need to teach doctors not to think of a person's chronologic age, but think of their functional age," Muss said.

Liefers said clinicians badly need a tool that can help them better calculate the optimal treatment for older women.

His findings, published in the Journal of the American Medical Association, also showed that as women got older, the chances of dying from something other than their breast cancer increased dramatically.

The encouraging finding for women of all age groups is that the vast majority will survive their cancer, Jones pointed out.

"The overall death rates are pretty low," he told Reuters Health. "I think that's a good message."

SOURCE: bit.ly/4HWZ7 Journal of the American Medical Association, February 8, 2012.

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