Women being treated postsurgically with tamoxifen (Nolvadex) to prevent breast cancer recurrence may also gain some protection against fatal coronary heart disease, according to a study reported in the June 4 Journal of the National Cancer Institute. The findings are consistent with results previously reported from Scottish and Swedish studies of adjuvant tamoxifen therapy for breast cancer.
The study was conducted by Joseph P. Costantino, DrPH, and colleagues at the University of Pittsburgh and the National Surgical Adjuvant Breast and Bowel Project (NSABP). This study involved women enrolled in the first phase of the multicenter, randomized clinical trial designated B-14, in which participants with early-stage breast cancer characterized by no lymph node involvement and estrogen receptor-positive tumors received (following surgery) either 5 years of tamoxifen therapy or a placebo. A total of 2,885 women were involved in the study, with an average follow-up of 8.9 years All deaths occurring in the study population were assessed to determine the cause. Three categories of heart disease-related death were defined: death from a definite fatal myocardial infarction, death from definite fatal coronary heart disease/possible myocardial infarction, or death from possible fatal coronary heart disease.
Overall, the average annual death rate from coronary heart disease was lower for patients who received tamoxifen than for patients who received placebo, but the difference was not statistically significant. The findings are consistent, say the authors, with both Scottish and Swedish studies that employed similar randomization and treatment protocols and that also suggested tamoxifen treatment reduces coronary heart disease among breast cancer patients.
Longer Follow-up Needed to Draw Definitive Conclusions
Costantino and colleagues emphasize, however, that longer follow-up of patients in all three trials is needed before definitive conclusions can be drawn about either short- or long-term effects of tamoxifen on heart disease, particularly among patients with breast cancer. They believe that the tamoxifen chemoprevention trials in healthy women, currently underway in the United States and Europe, will most likely be the only sources of randomized clinical trial data that will allow a direct evaluation of tamoxifens effect on heart disease risk that is not confounded by the biological effects of cancer and/or cancer treatment.
In an editorial accompanying the study report, V. Craig Jordan, PhD, DSc, Northwestern University Medical School, Chicago, states that the nonstatistically significant differences in coronary heart disease risk observed by Costantino and colleagues are not surprising. According to Jordan, this is because only about one-third of the women studied were over 60 years of age, when the positive effects (eg, reduced heart disease and osteoporosis risk) of hormone replacement therapy are profound. He believes that the key, and highly reassuring, finding of the study is that tamoxifen, which acts as an antiestrogen in the breast but has estrogenic effects on other body tissues, does not increase coronary heart disease risk in young women with breast cancer either during or after treatment.