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2015 San Antonio Breast Cancer Symposium: Arimidex, Tamoxifen, and Recurrence Risk After DCIS
Marisa Weiss, M.D.
December 15, 2015

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In this podcast, Marisa Weiss, M.D.,’s chief medical officer, explains a study that looked at the effectiveness of Arimidex and tamoxifen for reducing risk after DCIS surgery and radiation, as well as the side effects of each medicine. The study was presented at the 2015 San Antonio Breast Cancer Symposium, December 8-12. Listen to the podcast to hear Dr. Weiss explain:

  • what DCIS is
  • why postmenopausal women should be reassured no matter which of these medicines they’re taking
  • the side effects of each medicine

Running time: 11:26

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This podcast was made possible by the generous support of Lilly Oncology.

Jamie DePolo: Hello, everyone. Welcome to this edition of the podcast. I’m Jamie DePolo, the senior editor at Joining me today is Dr. Marisa Weiss. She is the chief medical officer here at, and we are going to talk about two studies that looked at hormonal therapy after DCIS surgery in postmenopausal women. Both of the studies were presented at the 2015 San Antonio Breast Cancer Symposium. So, Dr. Weiss, it sounds like these studies were good news, because women now have choices in their hormonal therapy.

Dr. Marisa Weiss: Absolutely. So, for women who have DCIS, otherwise known as ductal carcinoma in situ, or non-invasive breast cancer -- the kind of breast cancer that grows inside the milk pipe but hasn’t yet figured out how to break through -- even women who have that very, very early type of breast cancer still have to make some big choices. So these two studies were in postmenopausal women, as you noted, and in the NSABP B-35 study and in the IBIS study, the women in each group were randomized between Arimidex, also known as anastrozole, or tamoxifen, and it’s for women who specifically had hormone-receptor-positive DCIS.

Jamie DePolo: Okay, and most DCIS is hormone-receptor-positive? Is that right?

Dr. Marisa Weiss: Yeah, just like most invasive cancer is, too. So, in the study, there are over 3,000 women in the NSABP B-35 study, and they first looked at how well does anastrozole do compared to tamoxifen, and again, you might know anastrozole is Arimidex. And it turns out that the two medicines were about equally effective for the women in general, postmenopausal women who had lumpectomy, most had radiation, after a diagnosis of DCIS.

And what they found was that, overall, the medicines worked very well at lowering the risk of ever having a recurrence of DCIS or invasive breast cancer. In the women under 60 who are postmenopausal, the anastrozole did work somewhat better than tamoxifen. And it is also true that there are some differences in how women felt, their quality of life, you know, on this study. So, overall, the quality of life was very good for women in both arms, and in fact, the women on Arimidex compared to the women on [tamoxifen] had very similar quality of life levels.

Jamie DePolo: Let me ask you a question. Is one of those medicines -- I know Arimidex is an aromatase inhibitor; tamoxifen is not. Are one of those medicines right now the standard treatment after DCIS surgery?

Dr. Marisa Weiss: So, basically, the first medicine to be tested for its ability to lower the risk of recurrence after a diagnosis of DCIS was tamoxifen, and that’s a medicine that blocks estrogen from getting into the hormone receptors in the breast cancer cells. And so they wanted to know, since the aromatase inhibitors -- those are the medicines that block the production of estrogen in a woman after menopause -- since those medicines are doing a little bit of a better job in women with invasive breast cancer, the question was, “Okay, well, maybe they could do a better job in postmenopausal women who have just DCIS,” and it’s an important question to ask.

So this study, the B-35 NSABP study, as well as the next one we’ll get to, look at that question. And so, in this particular study, NSABP B-35, the medicines both worked well. And as I said, the aromatase inhibitor, Arimidex, anastrozole, worked a little bit better than tamoxifen in women under the age of 60.

And knowing that these two medicines are both important and that women are taking them once a day for 5 years during an important part of their life -- and these are very active women -- they wanted to take a good look at quality of life. Because you want to feel better, you want to feel like yourself. You want to be independent, function fully, feel good about each day.

Jamie DePolo: And both medicines are known to have side effects, right?

Dr. Marisa Weiss: Right, and I’m glad you asked that because in the study we’ll get to in a sec, most women have side effects while they’re under treatment, and women tend to attribute that side effect to the medicines they’re taking at that time. But we know that just growing old or going through menopause... you know, you can hit a lot of bumps in the road as well.

Jamie DePolo: You’re going to have some hot flashes usually, right?

Dr. Marisa Weiss: Yeah. The aches and the pains, the vaginal dryness, the bone loss, and fracture rate is elevated. The hot flashes, as you say. All those things happen normally naturally as women go through menopause, but it is true they happen more often in women who are taking anti-estrogen therapy like Arimidex/Aromasin and tamoxifen in the postmenopausal years.

So it’s not such a surprise that the women who were postmenopausal up to age 60, who are closer to being premenopausal, felt more of the symptoms than the women who were over 60. Because they’re still going through a transition of being from premenopausal to postmenopausal, and it can be a rocky road. For some women, it’s a roller coaster ride, right? So, in general, women who were on tamoxifen had more problems with hot flashes, some bladder control issues, and some GYN-like symptoms, and the women who were on Arimidex had more musculoskeletal problems like aches, and pains, fractures, as well as vaginal symptoms like vaginal dryness.

Jamie DePolo: And that’s not surprising, right? Both of those groups of side effects are typical for each medicine, right?

Dr. Marisa Weiss: Yeah. Those are pretty commonly reported side effects for any woman growing older and, for sure, more common in women on these medicines. And while it was true that symptoms on one medicine were somewhat different from another, particularly in a younger group of postmenopausal women, like under age 60, the differences weren’t huge or anything. They were statistically significant; they weren’t huge. But in general, the quality of life was the same for overall physical health; mental health, including depression, energy level and fatigue; and overall sexual functioning, were about the same.

But as I said, for under age 60, women felt the bumps in the road a little bit more. But I do want to point out that -- and this is really true for my own medical experience as a doctor taking care of these women and also personally: I, as you know, am a breast cancer survivor myself; so I’m the dual citizen -- I’m amazed by how differently each woman first, experiences life itself, right, and growing older is so individual and personal, right? In fact, you couldn't get anything more personal. And then each woman can have a very different response to some of these medicines.

And so I think one of the outcomes of this study, B-35, and the one I’ll touch on in a minute, is that women have choices. And you, for example, might do perfectly well on Arimidex, and I might do much better on tamoxifen. And there are other medicines, too, that women can choose, and it is so individual. So I would just tell people listening in that, you know, if one of these medicines is really getting in your way of enjoying your life, then go talk to your doctor and say, “I’m committed to doing what I need to do to be healthy, but help me out here.”

Jamie DePolo: So it is possible to switch?

Dr. Marisa Weiss: Absolutely! I’ve switched.

Jamie DePolo: Okay. And you don’t have to be on one or the other for a specific period of time before you can switch, is that right?

Dr. Marisa Weiss: That’s right. When it comes to DCIS, we know nothing about switching. In terms of women who have invasive breast cancer, we know more about switching, but here I think you can feel confident that you can move from one to the other and still have a very effective treatment regimen, and one may be much more tolerable than the other.

Just the other study, the IBIS study, that also looked at Arimidex versus tamoxifen in postmenopausal women with hormone-receptor-positive DCIS...

Jamie DePolo: It sounds very familiar.

Dr. Marisa Weiss: Yup, and again, both of these groups, they were treated with lumpectomy, most had radiation -- that, in this study, follow-up out to just over 7 years, that the Arimidex worked just about as well as tamoxifen. So, again, these are equally effective choices. And this study really showed that about 90% or so of women or more had some of these symptoms. I mean, they’re pretty common symptoms, again, for any of us as we move into the postmenopausal years, but particularly if you’ve had these medicines.

And in this study, they found that in the Arimidex people, anastrozole people, again, more fractures, more musculoskeletal issues, cholesterol was higher. This group, there were more strokes. And then on tamoxifen, more women had muscle spasms, and there’s the endometrial cancer issue -- which is not even a symptom; that’s a real problem -- GYN symptoms, hot flashes, and blood clots, which can be serious.

So I think the take-home message from these studies are that, for women with DCIS, it’s hormone-receptor-positive, we know already that after a lumpectomy alone, no further treatment, they all do very well. But that if they want to take steps to further reduce the risk of ever having a recurrence of DCIS or invasive breast cancer, then these medicines, Arimidex, or anastrozole that’s called, both names, and tamoxifen are about equally effective at lowering the risk.

One study showed that under age 60, maybe Arimidex/anastrozole outperforms tamoxifen and that each tends to have side effects that are shared, and there are some that are separate. And again, as I said, individually, you may tolerate one more than the other.

So if you’re committed to your plan and you talk to your doctor to choose one or switch from one to the other to improve your quality of life, that’s a very reasonable thing to do.

Jamie DePolo: Excellent. Excellent. Thank you so much, Dr. Weiss. That was a great explanation, and I hope all the women listening out there realize, yes, you have a choice. Talk to your doctor. You’re having unacceptable side effects, it’s perfectly fine to switch because you’re still getting a good medicine.

Dr. Marisa Weiss: Exactly, and thank you for having me.

Jamie DePolo: Thank you.

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