Adjuvant Endocrine Therapy for Women with Hormone Receptor Positive Breast Cancer Guideline

An interview with Dr. Jennifer Griggs from University of MIchigan on Adjuvant Endocrine Therapy for Women with Hormone Receptor Positive Breast Cancer: ASCO Clinical Practice Guideline Focused Update. This guideline provides recommendations on extended adjuvant therapy. on particular, use of aromatase inhibitors in women who had completed five years of adjuvant endocrine therapy.

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Hello, and welcome to the ASCO Guidelines podcast series. My name is Shannon McKernin and today I'm interviewing Dr. Jennifer Griggs from the University of Michigan, senior author on "Adjuvant Endocrine Therapy for Women with Hormone Receptor Positive Breast Cancer: ASCO Clinical Practice Guideline Focused Update." Thank you for being here, Dr. Griggs.

And thank you for the opportunity to talk about this focused update to the guidelines on extended adjuvant therapy. I would, of course, like to thank all my co-authors in the ASCO guidelines team for their contribution to this effort.

So first, can you give us a general overview of what this guideline covers and their research which informed this focus update?

Yes. First of all, the goal of the guideline was to give an update to the previous guidelines on this topic. And we specifically focused on extended adjuvant therapy. In particular, the aromatase inhibitors in women who had completed five years of adjuvant endocrine therapy. And it goes without saying, but it's worth reminding our listeners that the guideline is restricted only to post-menopausal women with hormone receptor-positive breast cancer. And, of course, our guidelines are only as good as the data upon which we rely. So for this guideline, six phase III randomized controlled trials met the pre-specified eligibility criteria for the updated systematic review and provide the evidence base for the guideline recommendations on the duration of aromatase inhibitor therapy. Each of the trials used the standard doses of the drugs that we use in practice today. So I'm not going to say the doses of each of the medications. So I'm going to go briefly over those six trials and just describe them so everybody's up to date with how the studies were designed.

So briefly, the first trial I'll describe is MA17R, which compares letrozole to placebo for five years in over 1,900 women who had already received 4.5 to six years of adjuvant therapy with an AI, proceeded in most women by treatment with tamoxifen. The second study is NSABP B-42. And this also compares letrozole to placebo in nearly 4,000 women who'd completed five years of endocrine therapy with either five years of an aromatase inhibitor or up to three years of tamoxifen followed by an aromatase inhibitor, for a total of five years.

The third study that we looked at is the DATA trial, which stands for the Different Durations of Adjuvant Anastrozole Therapy. This trial compared six years of adjuvant anastrozole with three years of adjuvant anastrozole in over 1,600 women after two to three years of adjuvant tamoxifen. The fourth trial out of the six is the IDEAL trial, the Investigation on the Duration of Extended Adjuvant Letrozole. This study randomized over 1,800 women to either 2 and 1/2 or five years of letrazole after five years of tamoxifen, an AI, or a combination in sequence of tamoxifen and an AI. So very similar study designs.

The fifth study is the ABCSG-16 trial, the Austrian Breast Cancer Study Group Trial 16, which randomized nearly 3,500 women following four to six years of adjuvant therapy with tamoxifen and AI or a sequence of tamoxifen and then an AI, to either two or five years of anastrozole as extended therapy. And finally, the study of letrozole extension, or the SOLE trial, randomized over 4,800 women with node-positive breast cancer who had completed five years of adjuvant endocrine therapy to receive either continuous letrozole for five years or five years of an intermittent schedule of letrozole given nine months on and three months off in years one to four and on continuously for a year or five.

So I know that's a lot to take in, but I do think it was important for our audience to understand the six trials that were included. These were all large studies, randomized, and patients had completed five years of adjuvant endocrine therapy. And then, were randomized either to placebo or different durations of an aromatase inhibitor or a placebo. For all of these studies, it's important to know that the primary outcome was disease-free survival. Overall survival and adverse events where secondary outcome.

Great. So given that research and those trials, what are the key recommendations for this guideline update?

Five key recommendations are included in this focused update to the previous guidelines. And they are for women with node-negative breast cancer, extended adjuvant aromatase inhibitor therapy can be offered for up to a total of five years of adjuvant therapy. Recommendations are based on considerations of recurrence risk using our usual established prognostic factors. However, since the recurrence risk is lower, the benefits are likely narrower in node-negative patients.

The guidelines panel recommends that women with low-risk, node-negative tumors should not routinely be offered extended adjuvant therapy. Now, that might sound vague. We did not make recommendations using genomic profiling results because we don't have sound data to support such views that we felt were strong enough to integrate genomic testing results. Our second recommendation is that women with node-positive breast cancer should be offered extended AI therapy for up to a total of 10 years of adjuvant endocrine therapy. And that means combined tamoxifen and aromatase endocrine therapy. That's the total that we meant to recommend.

Third recommendation is that women receiving extended adjuvant endocrine therapy should receive no more than 10 years of total treatment. The fourth recommendation is when given as prevention of secondary or contralateral breast cancer, the risk of second breast cancers based on prior therapy should inform the decision to pursue extended therapy. So what this means is specifically, a woman who has had a bilateral mastectomy will not reap the benefit of preventative therapy with endocrine therapy.

The fifth recommendation is that extended therapy carries ongoing risks and side effects, and these should be weighed against the potential absolute benefits of longer treatment in a shared decision-making process between the clinical team and the patient. Specifically, to date, none of the studies have shown improvement in overall survival with longer duration aromatase inhibitor therapy. As such, the recommendations, therefore, an extended adjuvant AI therapy are based on benefits that include prevention of distant recurrence and prevention of second breast cancers.

So why is this guideline so important and how will it change practice?

The importance of this guideline rests in the fact that it supports what many clinicians and patients are already doing in practice. The second is it recommends against durations of endocrine therapy longer than 10 years in the absence of data supporting such a practice. So it's our thought that doctors and patients and other care providers, nurse practitioners, physician assistants, primary care doctors, are already practicing what we're recommending, and it supports doing so. And the second is that for those providers and patients who aren't sure that 10 years is enough, this guideline suggests that 10 years is sufficient. We don't have any data supporting giving more than 10 years.

And the third recommendation is that this guideline really supports the need for shared decision-making, given the absence of data supporting an improvement in overall survival.

So finally, since you did mention shared decision-making, how does this guideline recommendation affect patients?

Well, the panel strongly believes that the tailored decision-making process is key in the decision to recommend extended adjuvant therapy. So tailoring on disease factors plays a role in the recommended duration of therapy. Obviously, since we stratified by high-risk and low-risk and what treatment's been received specifically. And if a woman's had bilateral mastectomy, she's not going to benefit from the risk reduction that's achieved with giving somebody extended therapy.

But in addition to disease factors, patient preferences and tolerance of therapy should inform clinician and patient decision-making. Again, since none of the studies have shown improvement in overall survival with longer duration of AI therapy, patients and their medical providers need to make decisions based on an awareness that the benefits include, specifically prevention of distant recurrence and prevention of second breast cancers. And the importance of those benefits is going to vary according to a patient and how she views her life going forward and how bad her side effects have been, how well she tolerates the therapy.

From my own personal point of view, as a breast oncologist, I believe two things. Number one, we should provide aggressive support for managing symptoms in patients who are most likely to benefit from extended therapy. That is, we should not stop therapy early if she is very likely to benefit if we haven't maximized control of her symptoms. There are many things we can do to improve symptoms and we shouldn't just stop therapy because she's not tolerating treatment if we haven't done the most that we can to improve her quality of life and her symptoms.

Conversely, my hope is that we are not doggedly persisting in recommending prolonged therapy in a patient who has a fear of recurrence but who has little to gain from extended therapy. In the latter case, high quality information support is more therapeutic than extended therapy with a medication that's proven, in randomized controlled trials and in her own personal experience, to decrease her quality of life with marginal, if any, medical benefit.

Thank you so much for the overview of this guideline today and thank you for your time.

Thank you.

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