Kathy D. Miller, MD


May 24, 2016

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Hi, it's Dr Kathy Miller, back with a little preview of what you might expect from the breast cancer sessions at ASCO this year. There are two studies being presented that I hope will answer some of our longest-running arguments in the field.

The first question: How long should patients continue an aromatase inhibitor in the adjuvant setting? We saw data several years ago with tamoxifen in the ATLAS[1] and aTTom[2] trials showing that 10 years had greater benefit than 5 years. Now, will the aromatase inhibitors take advantage of a similar pathway? They're very different drugs. They have a different mechanism of action and different toxicities. What the optimal duration of therapy might be for tamoxifen doesn't really tell us much about the optimal duration of therapy for the aromatase inhibitors.

At the plenary session this year, we'll get our first look at the re-randomization of the MA.17 trial.[3] MA.17, you'll recall from several years ago,[4] was a large trial that looked at patients who were finishing 5 years of tamoxifen, randomly assigning them to 5 years of an aromatase inhibitor or no additional therapy. It found a significant improvement in outcome with that additional hormone therapy. The trial was amended to allow a re-randomization, so as patients finished 5 years of an aromatase inhibitor, either as upfront therapy or after switching after tamoxifen, they were randomly assigned to an additional 5 years or to no additional therapy. Whether the results are positive or negative, or inclusive, the results are definitely important, and they'll be our first look at actual data to address this important and frequently asked clinical question.

Our second question, hopefully about to be answered, is: What is the role for anthracyclines in patients with HER2-negative breast cancer? Subsets of those early anthracycline trials done long before we understood about HER2 suggested that maybe it was only those patients with HER2-positive tumors who derived benefit. But those subset analyses were never conclusive and they were dramatically underpowered. So we will get the results of the first trial—and probably the only trial—that will ever be done that will compare anthracycline vs nonanthracycline treatment in patients with HER2-negative breast cancer.[5] This is a trial with a complicated design. It went through several amendments and changes that are likely to complicate the interpretation. But these are also the only data we're likely to get to address this really important question. As with the MA.17R trial, it might not end the arguments, but we'll finally actually have some data to argue, instead of just opinions.

I'm sure there'll be more, but those are the two most important breast cancer studies that I'm looking forward to. If you see me at ASCO, please stop and say hi. I'd love to get your thoughts on these studies and other aspects of the meeting.


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