NEW YORK (Reuters Health) - Postmenopausal women with breast cancer who successfully complete 5 years of tamoxifen therapy derive significant benefit from an additional 3 years of therapy with the anastrozole, an aromatase inhibitor, according to study findings published in the Journal of the National Cancer Institute.
Dr. Raimund Jakesz, of Vienna Medical University and members of the Austrian Breast and Colorectal Study Group, randomly assigned 856 hormone receptor-positive breast cancer patients, who were disease-free following primary surgery and 5 years of tamoxifen therapy, to 3 years of anastrozole or no further treatment.
After approximately 5 years, the women who received anastrozole had a statistically significant 38 percent reduced risk of local and regional recurrence; cancer in the other breast; and distant spread of the disease, compared with women who received no further treatment.
However, there was no significant difference in overall survival between the treatment groups.
Three years of anastrozole following 5 years of tamoxifen was generally well tolerated and “no unexpected adverse events were reported,” Jakesz and colleagues note.
They suggest that the “more manageable side effect profile of anastrozole compared with tamoxifen may allow the duration of adjuvant treatment to extend beyond the 5-year period recommended for tamoxifen.”
In an accompanying editorial, Drs. Tatiana Powell and Vered Stearns of Johns Hopkins University School of Medicine, Baltimore, say these results offer additional support for extending the duration of therapy with tamoxifen followed by an aromatase inhibitor to 8 years.
“However, whether such a course of extended adjuvant therapy is superior to either aromatase inhibitor monotherapy or shorter courses of sequential therapy is presently unknown,” they add.
Powell and Stearns also point out that while the safety profile of extended therapy with an aromatase inhibitor “appears to be generally acceptable,” the increasing use of these drugs has suggested the prevalence and severity of musculoskeletal side effects may be underestimated.
Recent observational studies, the physicians note, have shown that nearly half of the patients taking aromatase inhibitors experienced symptoms of joint pain and stiffness. One quarter of these symptoms were described as severe and up to 13 percent women stopped taking the medication within the first year because of these symptoms.
SOURCE: Journal of the National Cancer Institute, December 11, 2007.