Use of Endocrine Therapy for Breast Cancer Risk Reduction Guideline

An interview with Dr. Kala Visvanathan from Sidney Kimmel Comprehensive Cancer Center, and Johns Hopkins Bloomberg School of Public Health on the guideline update. This update adds anastrozole to the options of pharmacologic interventions for breast cancer risk reduction based on recent practice changing data. Read the full guideline at www.asco.org/breast-cancer-guidelines.

TRANSCRIPT

Hi. My name is Clifford Hudis, and I am the CEO of the American Society of Clinical Oncology as well as the host of the ASCO in Action podcast. About twice a month, I interview thought leaders in health care and experts in oncology. And we provide analysis and commentary on a wide range of cancer policy and practice issues. You can find the ASCO in Action podcast on Apple Podcasts or wherever you are listening to this show. And you can find all nine of ASCO's podcasts, which cover a wide range of educational and scientific content and offer enriching insight into the world of cancer care at podcast.asco.org.

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Hello, and welcome to the ASCO Guidelines Podcast series. My name is Shannon McKernin, and today I'm interviewing Kala Visvanathan from the Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, and Johns Hopkins Bloomberg School of Public Health, co-first author on "Use of Endocrine Therapy For Breast Cancer Risk Reduction: ASCO Clinical Practice Guidelines Update." Thank you for being here, Dr. Visvanathan.

Thank you as well for having me.

So can you tell us about the phase III randomized trial, which provided the signal for this update?

Yes. This was the IBIS-II trial that was reported out by Cuzick, et al in 2014. It was a double-blind, randomized placebo-controlled trial that assessed the safety and efficacy of Anastrozole, the aromatase inhibitor Anastrozole, at 1 milligram per day for five years. And the primary endpoint was the reduction of the incidence of breast cancer in postmenopausal women at increased risk of developing breast cancer. The trial itself was reported out with a median follow up of five years and the intention-to-treat analysis actually revealed that 85 women in the placebo group and 40 women in the Anastrozole group had developed both invasive and noninvasive breast cancer. What it showed was that there was a reduction in the incidence of breast cancer of 53% overall. It included both invasive and non-invasive breast cancer after a seven-year followup. And importantly, in subgroup analysis, similar to the other hormone endocrine therapy prevention trials, it also showed that the reduction in breast cancer risk among invasive cancers was limited to those individuals with ER-positive and PR-positive tumors. And the reduction in breast cancer incidence was among hormone-positive breast cancers. Another interesting point to mention here was that the five-year adherence was only slightly less in the Anastrozole arm compared to placebo. So it was well tolerated. And that was 68% in the Anastrozole group compared to 72% in the placebo group. And in all the subgroup analysis, there was no significant difference, except when they stratified by hormone replacement, women who had no prior hormone replacement, they saw a clear risk reduction. And this was not seen in women with prior hormone replacement therapy.

And so what are the key recommendations for the update of this guideline?

So based on these results, the update really adds Anastrozole as another option for endocrine prevention in women at increased risk. So specifically, we say that Anastrozole 1 milligram per day orally for five years should be discussed as an alternate to tamoxifen, raloxifene or exemestane in postmenopausal women for the reduction of breast cancer in women at increased risk. We also clarify further who are the women most likely to benefit from Anastrozole or the other endocrine prevention drugs. And these are women diagnosed with atypical hyperplasia, either ductal or lobular, or lobular carcinoma in situ or women with an estimated five-year risk of at least 3% based on the NCI Breast Cancer Risk Assessment tool or a 10-year risk of at least 5% based on the IBIS Tyrer-Cusick Risk Calculator. But we also give parameters for other risk models, and that is a relative risk of at least four times the population risk for women in the age group 40 to 45 and two times that of the population age group from 45 to 69. I think this is an important part of the recommendations, because up till now, the recommendations for women at increased risk have really followed the eligibility criteria for these trials, which were often a five-year risk, for example, of 1.7% in the NSABP trials. And here, we're trying to really highlight the importance of considering this women at higher risk where there is a clear benefit when you look at benefit-risk ratios. We also talk about the fact that Anastrozole should not be prescribed in women who are premenopausal and that it is really important that both patients and health care providers discuss the benefits and risks of Anastrozole along with the other risk-reduction agents when they are considering prescribing this. And then lastly, the importance of talking about specific adverse effects of Anastrozole, because here we're talking about a population of women at increased risk who are cancer free. And that includes baseline fracture risk, a measurement of bone mineral density as well as other adverse effects like joint stiffness, arthralgias, vasomotor symptoms, hypertension, dry eyes and vaginal dryness. So we think it's important that they have this discussion with women before the study.

So what are some of the clinical considerations for the use of endocrine prevention pharmaceutical agents for breast cancer risk reduction?

So in this guideline, we have introduced this section called Clinical Considerations to try to tackle some of the challenging questions that providers have when considering prescribing endocrine prevention. So I urge people to have a look at this section, because it's really a question-answer format. So one of the things we talk about first is what I just alluded to, how do you identify women at risk, where the benefit of endocrine prevention outweighs the risks? And we go through different risk calculations, and we give examples of clinical patients who fit into these risk categories. The second thing, which I think is an important thing, is we talk about a new study that came out while we were preparing this guideline update. And this was by De Censi, et al. And it's been published in the JCO on low-dose tamoxifen. This was a randomized trial in women with intra-epithelial neoplasia. So this includes women with atypical hyperplasia, lobular carcinoma, or ductal carcinoma in situ. So slightly different population. And the women were randomized to tamoxifen at 5 milligrams a day-- so this is 1/4 of the standard 20-milligram dose-- or placebo for three years. So remember-- or endocrine prevention trials were for five years. So this was a shorter duration. And then a median followup of five years, they reported out the results, and they saw half the number of neoplastic events, so DCIS or invasive cancer, compared to placebo. So the results were very comparable to the original NSABP-P1 trial and very promising. So the further I think, what has been a sometimes prevented uptake of these agents, has been the adverse effects of tamoxifen, for example, equal to uterine cancer. And in this study, they did not see an increase in the number of serious adverse effects, including deep venous thrombosis and endometrial cancer. They still saw an increase in hot flashes. So I think this is very promising data and could be an alternate option for some patients, where side effects are a problem or they're reticent to take prevention given the side effects. Another thing we tackle is the question of age when you start recommending hormone prevention. And here, this relates to we talk about at 70, not so much that you would stop it at 70, but at that age or 70 or above, you would actually make sure you're taking into consideration their life expectancy. So they should have a life expectancy of 10 years or greater. And you're also taking into consideration their breast cancer risk. So the question there was, is there an upper age limit for endocrine risk reduction therapy? And we think that, at least the panel thought that, in women 70 years of age or older, you should actually consider both the short-term risk. It should be at least in the range of 1% or more per year. So that would be women with atypical hyperplasia, a family history, or some with carcinoma in situ. We want to make sure they're active and that they have a life expectancy of 10 or more years. Another question we tackled here was, what is the duration of endocrine therapy in this setting for breast cancer risk reduction? And this comes in the context that now, in the treatment setting, a subset of women are given, for example, tamoxifen for more than five years. In terms of data, with the exception of raloxifene, where we do have longer-term data that is greater than five years, in women at increased risk of breast cancer from the osteoporosis prevention trial, where we see that even with women taking raloxifene for more than five years still have a benefit in terms of the breast cancer risk reduction. We don't really have data for any of the other agents in the preventive setting. So there is currently no data from randomized trials that any of these agents, except for raloxifene, should be given for longer than five years. And that is in the setting of women with osteoporosis. And then the last question that we tackle is to look at how you decide between taking an aromatase inhibitor endocrine prevention therapy or a SERM. And this is really only in postmenopausal women, because we still only have one option for premenopausal women, and that is tamoxifen. Here, we just go through step by step sort of the process of thinking about the side effects for each of these agents. And in the context of the woman who is considering endocrine therapy and tailoring it to their age, what symptoms they have, or other comorbidities.

Finally, how will these guideline recommendations affect conversations between providers and women at increased risk for breast cancer?

So I think, firstly, these guidelines, again, bring attention to breast cancer prevention and the need for us as a community, both providers and women, to move this field forward. And what do I mean by that is we need to be more systematic about identifying women who are truly at increased risk and then subsequently having these discussions with them about the options available. And so I think this guideline adds another agent to the list of agents we now have that can be used to reduce breast cancer risk or breast cancer incidence and also provide the opportunity to-- we look at this and think about how we might incorporate discussions on breast cancer risk reduction into clinical practice. We do also want to stress the importance of discussions on lifestyle factors or risk reduction in addition to these agents. So I think hopefully this guideline helps to, again, refocus attention on the issue and encourage both women to ask their providers about their breast cancer risk and then providers to re-look at this question about breast cancer prevention and how to identify those who are at risk and then discuss endocrine prevention in those at higher risk. I think this is particularly important as we think about our aging population and the increase we are expecting in breast cancer over the next 10 to 20 years. And then also, as we think about breast cancer is now the number-one cancer diagnosed, well, the prevention becomes even more important.

Great. Thank you for your work on this guideline. It sounds like there may be many important conversations which happen between women and their providers based on the work and the research about breast cancer risk reduction. So thank you again for coming on the podcast to share with us today, Dr. Visvanathan. Thank you. I would like to thank ASCO for having these podcasts and also shining a light on breast cancer prevention and getting this information out to its listeners.

And thank you to all of our listeners for tuning into the ASCO Guidelines Podcast Series. To read the full guideline, go to www.asco.org/breast-cancer-guidelines. And if you've enjoyed what you've heard today, please rate and review the podcast and refer the show to a colleague.