New guidelines issued for endocrine treatment of breast cancer

July 13, 2010

Postmenopausal women with hormone receptor-positive breast cancer should use an aromatase inhibitor (AI) at some point during their adjuvant (post surgery) treatment, either up front or as sequential treatment after tamoxifen, to lower their risk of recurrence, recommends a committee convened by the American Society of Clinical Oncology (ASCO).  In updated guidelines published online in the Journal of Clinical Oncology, the committee also gives the green light for extended use of AIs, after five years of tamoxifen.  The committee carried out a systematic review of studies, including twelve major trials, and found that the use of an AI was associated with a lower risk of recurrence, though the impact was modest. 

"In comparison to 5 years of tamoxifen alone, use of an AI in either primary, sequential, or extended treatment (given after five years of tamoxifen) improves disease-free survival and reduces the risk of breast cancer events, including distant recurrence, locoregional recurrence, and contralateral breast cancer. In absolute terms, the reduction in risk of recurrence associated with AI-based therapy compared with tamoxifen is modest, typically amounting to less than 5% through multiple years of follow-up," the committee members report.

Though slight differences in disease recurrence showed up in several studies, no differences were found in overall survival between tamoxifen and AI-based therapy when used as either a primary treatment or extended therapy.  Two of the six trials of sequential treatment strategies did show a slight, statistically significant improvement in overall survival compared with tamoxifen alone. 

"Breast cancer events such as locoregional recurrence, contralateralbreast cancer, and early distant metastatic recurrence are clinically important to patients. For this reason, the Update Committee recommended consideration of AI therapy at some time during adjuvant endocrine therapy even though few trials demonstrated statistically significant differences in overall survival," the report says.

The studies clearly showed different side effect profiles for each drug and the committee recommends patient preferences be considered when choosing the endocrine therapy strategy. The optimal timing and duration of AI and/or tamoxifen use remains unresolved, the committee also reports.