Tamoxifen or aromatase inhibitors? It's a treatment decision for postmenopausal women with hormone-receptor positive breast cancer. Three recent studies compared tamoxifen to aromatase inhibitors in terms of survival, toxicity and tumor activity. Links to all studies and media coverage may be found on the Arimidex page of the LATESTBreastCancer.com website.
Adjuvant therapy: Aromatase inhibitor toxicity and overall survival
When used as adjuvant therapy to prevent recurrence, aromatase inhibitors (AIs) are associated with improvements in disease-free survival, but not overall survival. A review in the Journal of the National Cancer Institute, first published online July 8, examined whether differences in toxicity explain the difference in overall survival. Yesterday, Medical News Today and medpagetoday.com covered the results.
The review included 7 trials and 30,023 patients. Longer use of AIs was associated with increased odds of cardiovascular disease and bone fractures, but decreased odds of venous thrombosis and endometrial cancer. Five years of AIs was associated with an increase in the odds of death without breast cancer recurrence compared to 5 years of tamoxifen or 2-3 years of tamoxifen followed by AIs. However, the difference was not statistically significant.
The authors concluded that when used alone, "cumulative toxicity" of AIs may explain the lack of overall survival benefit despite improvement in disease-free survival. Switching from tamoxifen to AIs "reduces this toxicity and is likely the best balance between efficacy and toxicity."
Advanced breast cancer: Aromatase inhibitors vs. tamoxifen
A review in Clinical Breast Cancer, first published online July 7, compared aromatase inhibitors to tamoxifen as first-line therapy to treat advanced breast cancer. The review included 6 trials with 2,560 patients. Aromatase inhibitors had a significantly better overall response rate and clinical benefit. There was a trend towards improved overall survival, but it was not statistically significant. Toxicities did not differ significantly, except vaginal bleeding and thromboembolic events.
The authors concluded that AIs "appeared to be effective and feasible compared with tamoxifen as first-line hormonal therapy in postmenopausal women with advanced breast cancer." They noted that further, randomized, controlled trials are necessary.
PET scanning reveals differences in anti-estrogen activity
How effective is hormonal therapy in blocking estrogen activity?
A July 15 Clinical Cancer Research study used PET scanning to monitor how tumors in metastatic patients responded to tamoxifen, Faslodex (fulvestrant) and aromatase inhibitors such as Arimidex, Aromasin or Femara. This week, DOTMed News and Medical News Today covered the study.
Thirty women with metastatic breast cancer underwent PET scan imaging. Uptake of an estrogen-containing contrast agent was used to assess estrogen binding. A decline in uptake meant less estrogen binding. Tumor uptake "declined more markedly" with tamoxifen and Faslodex than with aromatase inhibitors. Tamoxifen was more effective than Fulvestrant in complete tumor blockade of estrogen.
The authors concluded that PET scanning "can assess" the pharmacodynamics (what a drug does to a body) and "give insight" into the activity of estrogen-receptor targeted agents. "Imaging revealed significant differences between agents," including differences in blockade.
Dr. Hannah Linden, a study author, was quoted in both media stories to say, "What we're suggesting in the paper . . . is if estrogen is incompletely blocked you're not getting a good outcome for the patient."
We'll continue to follow hormone therapy research. We review medical journal abstracts and media sources daily. All the latest news and research on any breast cancer test or treatment option may be found on the treatment pages of the LATESTBreastCancer.com website anytime.