Today at ASCO: Anastrazole Offers Higher Breast Cancer-Free Survival Rates than Tamoxifen Following DCIS, Phase III Study Shows

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Results of NSABP, Allegheny Health Network-led trial suggest anastrazole may be an effective additional option for breast cancer prevention.

Thomas B. Julian, MD

"This is good news for breast cancer prevention, and good news for women who are seeking an alternative to tamoxifen." Thomas Julian, MD, Director of Breast Surgical Oncology, Allegheny Health Network

Note: Dr. Julian is available for interviews today on this new development in breast cancer prevention.

A phase III trial funded by the National Institutes of Health suggests that postmenopausal women with ductal carcinoma in situ (DCIS) now have an additional tool for breast cancer treatment and prevention.

The study (NSABP B-35/NRG Oncology) looked at more than 3,000 DCIS survivors, comparing those who completed the standard five-year treatment with tamoxifen to those who completed five years of the aromatase inhibitor anastrazole. The anastrozole group showed 10-year breast cancer-free survival statistically significantly higher than rates in the tamoxifen group.

The Allegheny Health Network was a trial site for the study, conducted by the Pittsburgh-based National Surgical Adjuvant Breast and Bowel Project (NSABP). Co-authors included Thomas Julian, MD, Director of Breast Surgical Oncology at AHN and Senior Surgical Director of Medical Affairs at NSABP, and Norman Wolmark MD, NRG Oncology Chairman and breast surgical oncologist.

The results were presented at the annual conference of ASCO, the American Society of Clinical Oncology, May 29-June 2 in Chicago.

“This is good news for breast cancer prevention and good news for women who are seeking an alternative to tamoxifen,” Dr. Julian said. “Both are very effective, but toxicity seems to be lower with anastrazole. Women should discuss the various options for breast cancer prevention, including side effects, with their physicians.”

This is the first study to compare tamoxifen with an aromatase inhibitor in women with DCIS. Tamoxifen blocks estrogen, and anastrazole lowers estrogen, both ways interfering with cancer cell growth.

The study randomly assigned 3,104 postmenopausal, hormone receptor-positive DCIS survivors to daily tamoxifen or anastrazole for five years. All had undergone lumpectomy and radiation therapy.

After an average follow-up period of 8.6 years, 114 breast cancers were detected in the tamoxifen group compared to only 84 in the anastrazole group. The 10-year breast cancer-free rates were better in the anastrazole group than in the tamoxifen group (93.5% vs. 89.2%), a statistically significant difference.

Ten-year overall survival rates were comparable in the two groups (92.5% for anastrazole and 92.1% for tamoxifen). The results also revealed that anastrazole appears to be superior to tamoxifen in women younger than age 60 and equal in women older than age 60.

Generally, aromatase inhibitors such as anastrozole are less toxic than tamoxifen, though anastrozole is slightly more likely to lead to bone fractures, but shows similar results with muscle ache and pain. The most serious but rare side effects of tamoxifen are an increased risk of uterine cancer and blood clots, both of which were lower for anastrozole in this study.

About the Allegheny Health Network:
Allegheny Health Network, part of Highmark Health, is an integrated healthcare delivery system serving the Western Pennsylvania region. The Network is comprised of eight hospitals, including its flagship academic medical center Allegheny General Hospital, Allegheny Valley Hospital, Canonsburg Hospital, Forbes Hospital, Jefferson Hospital, Saint Vincent Hospital, Westfield Memorial Hospital and West Penn Hospital; an employed physician organization, a research institute, health + wellness pavilions, home and community-based health services and a group purchasing organization. The Network employs approximately 17,500 people, and has more than 2,100 physicians on its medical staff. The Network also serves as a clinical campus for both Temple University School of Medicine and Drexel University College of Medicine. AHN also has established a collaborative relationship with Johns Hopkins Medicine to advance medical research and explore opportunities for improving patient care quality, access and affordability.

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Stephanie Waite