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By William Peters, M.D., Ph.D.

08/14/2018

Which breast cancer patients benefit from adjuvant chemotherapy?

In 2000, the National Institute of Health recommended that the majority of women with localized breast cancer received adjuvant chemotherapy. While it was clear to many of us in the medical profession that the benefit of chemotherapy was only for a small subset of women, the tools for identifying the right patients weren’t available. 

Over the last 15 years, studying the genetic features of breast cancers has improved the ability to identify which patients benefit from adjuvant treatment after their surgery and radiation therapy for breast cancer. The use of a laboratory test called OncotypeDX provides a numeric result called “Recurrence Score”, or RS, which is based on the presence or absence of various genes. This test predicts how patients will respond to endocrine and chemotherapy for their breast cancer. Previous studies had shown that patients with a low RS (10 or less) will do well with endocrine therapy alone, while patients with a high RS (over 32) get a significant benefit from adding chemotherapy to endocrine therapy. 

For a large group in the middle with an “intermediate” RS between 10 and 32, it wasn’t clear whether endocrine therapy was enough or if both chemotherapy and endocrine therapy were needed. A new study, TAILORx, has finally answered this question. In the study, more than 10,000 women with breast cancer that did not involve axillary lymph nodes and had an “intermediate RS” between 11 and 25 were randomized to either receive endocrine therapy alone or a combination treatment of chemotherapy and endocrine therapy.

There are several important findings from this study:

First, this study confirmed that the prognosis is extremely positive for patients with breast cancers with a low recurrence score (RS  10 or less) in this test – almost 98% survival at 7.5 years of follow-up with endocrine therapy alone. This means that for this large fraction of patients that have a good RS result, the long- term outcome with oral endocrine (hormonal) therapy alone is terrific.

Second, the study found that most patients with an intermediate RS between 11 and 25 did very well with just endocrine therapy compared with the combination of chemotherapy and endocrine therapy – despite the higher “RS”, 95% of the women had no distant recurrence. So just hormonal therapy will give an excellent outcome for a large group of patients without the need for chemotherapy. Importantly, these results were not affected by the grade or size of the tumor.

There were some differences in outcomes for younger women (under 50 years old) who had fewer distant recurrences with chemotherapy when the RS was over 16, and particularly when it was over 20. This means that a careful discussion with your physician about what treatment to use is very important for women under 50.  However, even this group of patients may largely be spared chemotherapy because endocrine treatment in younger women has substantially improved in recent years.

This TAILORx study was only in women with breast cancer with no involvement of axillary lymph nodes. A new study is underway to determine whether patients with one to three involved lymph nodes will also be spared the need for chemotherapy. 

A little more than 15 years after the National Institutes of Health recommended adjuvant chemotherapy for the majority of women with localized breast cancer, we now know that for many women, endocrine therapy alone after surgery and radiation can achieve excellent treatment outcomes. As always, the study raises new questions about how to manage the now much smaller group of patients where the benefit of chemotherapy is apparent. I believe that the future will give us even more precise genetic analysis and enable us to be even more selective, not only of who needs chemotherapy, but as to which type of chemotherapy would give these women the best outcomes.

If you have questions regarding treatment options for breast cancer, please call us at 904-880-5522.

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