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| |  Optimal Duration of Neoadjuvant Letrozole Longer Than the Traditional 4 Months to Permit Breast-Conserving Surgery: Presented at SABCS By Wayne Kuznar SAN ANTONIO, Tex -- December 11, 2009 -- The optimal duration of neoadjuvant letrozole to permit breast-conserving surgery in patients with early breast cancer appears to be much longer than the standard 4 months, according to an interim analysis presented here at the 32nd Annual San Antonio Breast Cancer Symposium (SABCS). The established 4-month duration for neoadjuvant letrozole in this population is derived more from the traditional length of chemotherapy rather than definitive data with endocrine agents. “Even though we know that endocrine agents don’t cause a response in the way that chemotherapy does, it just became conventional that 4 months was the time period that patients received it,” said principal investigator Rob Carpenter, MD, St. Bartholomew’s Hospital, West Smithfield, London, United Kingdom, here on December 10. Previous retrospective studies in the neoadjuvant setting, however, suggested that letrozole treatment for as long as 8 to 12 months resulted in significant tumour shrinkage in localised hormone receptor-positive breast cancer, setting the stage for the current multicentre, single-arm, open-label, phase 4 prospective study. In the study, postmenopausal women with primary invasive, oestrogen receptor (ER)-positive and/or progesterone receptor-positive breast cancer with large tumours (stage T2 or higher) that were initially not eligible for breast-conservation surgery were treated with letrozole 2.5/day. The primary endpoint was the time at which patients became considered eligible for breast-conserving surgery. The data presented here were from 103 women who had at least 1 post-baseline assessment of tumour response. The final analysis will include 117 patients; currently 83 have been confirmed as completing the trial. The optimal duration of therapy was indicated by sufficient tumour shrinkage for breast-conserving surgery, disease progression, or reaching a maximum of 12 months of treatment. The median time to breast conservation was 8.2 months. The initial response, during the first 4 months, was rapid, after which the rate of response slowed and remained constant for an additional 6 months. The response rate at 4 months was 9.4%, improving to 32.2% at 6 months. “At 4 months, a small proportion of patients, maybe 10%, will be ready for breast conservation,” said Dr. Carpenter. “That goes up to 70% by 10 months. This is potentially practice changing for the use of neoadjuvant letrozole for ER-positive patients who want to keep their breasts, when on presentation they would have been destined for mastectomy.” “The last patient in the trial will be through [with therapy] by January,” he said. “By looking at how strong the trend is in this study, I don’t think that the analysis of another 30 patients is going to change the final outcome.” [Presentation title: A Multicentre Study to Determine the Optimum Duration of Neoadjuvant Letrozole on Tumour Regression to Permit Breast Conserving Surgery: An Interim Analysis. Abstract 1082]
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