Breast cancer therapies' side effects vary by age

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breast cancerEven among relatively young women with early-stage breast cancer, the side effects of therapy can vary by age, according to a new study.

Past research has found that for some premenopausal women, breast cancer treatment with standard chemotherapy or a hormonal therapy with goserelin is equally effective. This includes women with early-stage cancers that are positive for estrogen receptors; in these cancers tumor growth is fueled by estrogen.

Goserelin treats breast cancer by blocking the action of estrogen on tumor cells, while chemotherapy directly kills cancer cells, as well as some healthy cells in process.

Since the two treatments are equally effective for certain women, the side effects are likely to be a prime factor in treatment decisions, according to the authors of the new study, published in the Journal of Clinical Oncology.

To compare the quality of life after each treatment, the researchers followed 874 women randomly assigned to receive chemotherapy, goserelin, or both for early-stage breast cancer. All of the women were either premenopausal or just beginning menopause.

Those on goserelin alone received monthly injections of the hormone for 2 years, while chemotherapy patients were on a three-drug combination administered every 28 days for 6 months.

The researchers, led by Dr. Jurg Bernhard of the International Breast Cancer Study Group Coordinating Center in Bern, Switzerland, found that women on goserelin generally reported better quality of life -- including less fatigue, less nausea, and a greater sense of well-being -- in the 6 months after starting therapy.

They did, however, have hormonal side effects, including loss of menstrual periods (amenorrhea) and hot flashes, sooner and more often than women on chemotherapy.

Among women younger than 40, nearly all had amenorrhea within 3 months of starting goserelin. In contrast, about half of those on chemotherapy experienced amenorrhea which developed more slowly.

Nearly all of the younger women on goserelin resumed their periods after they stopped therapy, whereas 35 percent to 40 percent of those on chemotherapy still had amenorrhea 3 years after starting treatment.

For women age 40 or older, the pattern was different. Most of those on chemotherapy eventually became amenorrheic and, for all but a few women, this turned into permanent menopause. Women treated with goserelin were more likely to resume their periods after treatment ended, but about half still had amenorrhea at the 3-year mark.

Women who received the sequential treatment of chemotherapy followed by goserelin experienced about the same side effects as those treated with chemotherapy alone. "The effects of chemotherapy appear to mask those of endocrine (hormonal) therapy," the researchers point out.

It's important for women to understand the different side-effect patterns of chemotherapy and goserelin, and how they vary by age, according to Bernhard.

"So far, age-related considerations have not received the attention they deserve," he told Reuters Health. Premenopausal women and those close to menopause are seen and treated as one group. "Our findings indicate that this is an oversimplification."

Relatively younger women may want to consider goserelin, according to Bernhard, because although it more often causes amenorrhea, it's reversible. It also allows women to avoid the toxicity of chemotherapy, he noted.

However, Bernhard added, very young women are likely to need chemotherapy because their cancer often has a worse prognosis.

SOURCE: Journal of Clinical Oncology, January 20, 2007.

Copyright © 2007 Reuters Limited

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