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ASCO endorses aromatase inhibitors for hormone-sensitive breast cancer

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – Updated guidelines issued by the American Society of Clinical Oncology (ASCO) recommend that postmenopausal women with hormone receptor-positive breast cancer should receive aromatase inhibitor therapy at some point in their course of treatment.

An expert panel co-chaired by Dr. Harold J. Burstein from the Dana-Farber Cancer Institute, Boston, Massachusetts, and Dr. Jennifer J. Griggs at the University of Michigan in Ann Arbor, systematically reviewed recent evidence on adjuvant endocrine therapy for postmenopausal hormone receptor–positive breast cancer, focusing on 12 major trials.

“An adjuvant treatment strategy incorporating an aromatase inhibitor (AI) as primary (initial endocrine therapy), sequential (using both tamoxifen and an AI in either order), or extended (AI after 5 years of tamoxifen) therapy reduces the risk of breast cancer recurrence compared with 5 years of tamoxifen alone,” the panel concludes in its report in the Journal of Clinical Oncology released online July 12.

While guidelines recommend adjuvant AI therapy at some point, “The optimal timing and duration of AI treatment remain unresolved; it is unclear whether sequential treatment strategies yield advantages over monotherapy with AIs.”

An ASCO press release also highlighted several other recommendations made by the committee:

–Tamoxifen should be given to all premenopausal and perimenopausal women; AIs are only effective in postmenopausal women. Women who are pre- or peri-menopausal at the time of diagnosis should receive 5 years of tamoxifen.

–There are no clinically important differences in effectiveness among the three commercially available AIs (anastrozole, letrozole, and exemestane).

–As tamoxifen is a selective estrogen receptor modulator while AIs deplete the production of estrogen in postmenopausal women, aromatase inhibitors may reduce the chance of blood clots and uterine cancer but may increase the risk of osteoporosis and fractures.

“The Panel emphasized the importance of discussing side effects of these drugs with patients, to help patients better understand and choose between the treatments and do all we can to maximize compliance with these important therapies,” said Dr. Griggs in the ASCO press release.

The clinical practice guideline and other clinical tools and resources are available at

ASCO has also developed a corresponding patient guide available on ASCO’s patient website,


American Society of Clinical Oncology Clinical Practice Guideline: Update on Adjuvant Endocrine Therapy for Women With Hormone Receptor–Positive Breast Cancer

J Clin Oncol 2010;