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  • Latest Research Findings from the 2012 San Antonio Breast Cancer Symposium – Benefits of Longer-Term Tamoxifen Use by Eric P. Winer, MD

    The 2012 San Antonio Breast Cancer Symposium (SABCS) attracted approximately 10,000 scientists and clinicians, all of whom spent five days thinking about little else other than breast cancer.  In truth, many, if not most, of the attendees spend their professional lives focused exclusively on breast cancer research, treatment and prevention. 

    The number of practice-changing presentations was limited, but there was a lot of excitement about the research that was presented.  There is a very strong sense that progress is being made, and that we are closer and closer to understanding the biology of different subtypes of breast cancer.  We know more than ever before about what makes a breast cancer grow and flourish, and armed with this information, we are better able to design new and better treatments.  A number of presentations focused on promising new drugs, and while these treatments will have to be tested in larger clinical trials, they offer great hope. 

    The single most practice-changing finding that was presented was related to the use of tamoxifen.  As most people know, tamoxifen is one of the mainstays of breast cancer treatment.  It was first used over 30 years ago, and it has saved more lives than any other breast cancer treatment.  A new worldwide study called ATLAS found that a 10-year course of tamoxifen prevented more breast cancer recurrences than 5 years of treatment.  In addition, the 10-year course prevented deaths from breast cancer and improved overall survival.   

    The benefits were modest, with a three percent decrease in the chance of having a recurrence.  But what makes this small benefit so important is that it was coupled with a decrease in deaths from breast cancer.  Although there was an increase in the risk of developing endometrial cancer in women who took the longer course of tamoxifen, there were very few deaths from endometrial cancer and the benefits of tamoxifen appeared to outweigh this risk. 

    For premenopausal women with hormone receptor-positive breast cancer, a course of 5 years of tamoxifen has been the standard treatment for almost two decades.   

    Women who are premenopausal at diagnosis and become postmenopausal before they complete 5 years of tamoxifen can go on an aromatase inhibitor when they finish tamoxifen, but those who remain premenopausal have had no option for extended therapy.  With these new findings, many premenopausal women may stay on tamoxifen for a total of 10 years.  Because endometrial cancer is extremely uncommon in premenopausal women who take tamoxifen, there are relatively few serious risks associated with a longer course of tamoxifen in premenopausal women.  Of course, the ultimate decision must be individualized and will require a discussion between the woman and her oncologist.  Women who are either at very low risk of recurrence or those who have troublesome side effects (such as hot flashes) on tamoxifen may decide to stop at the end of 5 years.  My sense, however, is that many women will continue treatment beyond 5 years.  Women who have already completed a course of tamoxifen and are off therapy may wish to talk with their oncologist about whether it makes sense for them to restart tamoxifen.  In truth, however, we do not know how effective the restarting tamoxifen would be in these women. 

    For postmenopausal women, the ATLAS findings are more “practice-influencing” than “practice-changing,” and this is because tamoxifen alone is not the usual treatment for most postmenopausal women with hormone receptor positive breast cancer.  At present, postmenopausal women typically receive either a 5-year course of an aromatase inhibitor or a 2-5-year course of tamoxifen followed by 2-5 years of an aromatase inhibitor.  For postmenopausal women who receive a 5-year course of tamoxifen, we know that an additional 5 years of an aromatase inhibitor is a beneficial treatment.  But, most postmenopausal women do not receive 5 years of tamoxifen.  They typically receive either 5 years of an aromatase inhibitor as initial therapy or 2 years of tamoxifen followed by 3-5 years of an aromatase inhibitor.  For these women, the new results suggest that a longer course of therapy may be beneficial, but since we do not have data on the use of aromatase inhibitors for more than 5 years, the ATLAS findings are of great interest but do not apply directly to these patients.  They raise the question as to whether some women should remain on an aromatase inhibitor for more than 5 years (this will be answered by ongoing clinical trials) or even if tamoxifen should be considered following 5 years of an aromatase inhibitor. 

    As with many studies, ATLAS raises many questions.  It will change the nature of conversations with patients in the clinic, and it will affect the design of future research studies.  And perhaps most importantly, it suggests that long-term hormone therapy has the potential to reduce breast cancer recurrences and improve survival. 

    Watch my discussion of the ATLAS study from the conference.    

    Learn more about hormone therapy

    Learn more about tamoxifen

    Learn more about aromatase inhibitors.  

    New Komen Reseach Blogs- A Year in Review

    Finally, as 2012 comes to a close, take a look at two of our newest blogs highlighting the advances in breast cancer research from 2012:  

    Research highlights included everything from mapping cancer genomes, to understanding old and new treatment combinations, extending use of current therapies, and much more.  These advances across the spectrum of care certainly give us hope for the future, as scientists around the world work to end breast cancer. 


    Posted December 20, 2012