The new research exposes the disparity between clinicians' reporting of side effects and women's actual experiences. In a previous study, clinicians reported 5 percent of their patients experienced moderate to severe symptoms as a result of taking aromatase inhibitors. The new Northwestern study surveyed 686 women with a detailed questionnaire about their symptoms before treatment and at three, six, 12 and 24 months after starting treatment. The researchers found after three months of treatment that 33 to 35 percent of women had severe joint pain, 28 to 29 percent had hot flashes, 24 percent had decreased libido, 15 to 24 percent had fatigue, 16 to 17 percent had night sweats and 14 to 17 percent had anxiety. These numbers increased as women were on treatment longer.

Earlier studies also asked women to recall their symptoms after treatment ended, which is less accurate than reporting them at regular intervals while taking the drugs.

As a result of the side effects, 36 percent of women ended treatment before an average of 4.1 years. After two years, 10 percent had quit; the remainder quit between 25 months and the 4.1 years.

"These findings can help us identify women at risk for quitting the therapy, counsel them about the importance of staying on it and provide treatment for troubling side effects," Wagner noted.

Weight gain can be addressed with nutritional counseling, while mood swings and irritability can be treated with cognitive behavioral therapy or mind-body techniques, Wagner said. Joint pain can be tempered with nonsteroidal anti-inflammatory drugs, or women may be switched to a different hormonal medication. Nausea can be reduced with medication.

For the study, patients who had postmenopausal breast cancer filled out a 46-question survey rating their quality of life and symptoms associated with breast cancer and endocrine treatment. The survey included an item asking how much they were bothered by side effects of treatment from zero (not bothered) to four (severely bothered). For each additional one-point increase on this item, the patient's risk of quitting treatment early rose 29 percent. The patients were randomized to take one of two hormonal treatments (anastrozole or exemestane) daily for five years.

Source: Northwestern University