Women 65 and older with breast cancer should consider chemotherapy even though doctors have been reluctant to use it in that age group because of the side effects, a study said on Tuesday.

Doctors at the Vermont Cancer Center in Burlington analyzed cases between 1975 and 1999 and found that “healthy older patients are likely to derive similar treatment benefits as younger patients” from chemotherapy.

The older group had “the same lowering of their relapse rate, and the same lowering of their breast cancer mortality rate, by being on a higher dose therapy. This was similar to younger patients,” said Hyman Muss, a doctor who headed the study.

The study, published in this week’s Journal of the American Medical Association, said that nearly half of all new breast cancers in the United States occur in women 65 or older.

But data, it said, suggests that chemotherapy may be underused in older patients or given at reduced doses that decrease its effectiveness, because of reactions that can leave patients weak, exhausted and nauseous.

“I would recommend that for older breast cancer patients ... they ask their physicians about the opportunities to receive chemotherapy that might be helpful to them,” Muss said.