Preventing Breast Cancer With A Pill: Q&A With Leading Specialist

Over the weekend, news broke from a big cancer conference in Chicago that exemestane, a hormone-blocking Pfizer drug used to keep breast cancer from coming back, appears to work to help prevent it as well.

Carolyn Johnson of The Boston Globe reported:

“There was a 65 percent reduction in the risk of breast cancer — a pill that can do that to the commonest cancer that affects women globally and kills women globally; there’s no such pill that I know of for any kind of cancer,’’ Dr. Paul E. Goss, director of the breast cancer research program at Mass. General and lead author of the study, said in an interview before presenting the findings at the meeting of the American Society of Clinical Oncology in Chicago.
“We haven’t seen any serious toxicity that might stifle someone’s decision to try and take this drug,’’ said Goss, who has received honoraria from several pharmaceutical companies, including a one-time speaker’s fee from Pfizer.

So is exemestane about to become the new statins for women over 50? The next pills that huge swaths of the population take to fend off diseases that tend to rise with age? For expert outside comment, I turned to Dr. Eric Winer, director of the breast program at the Dana-Farber Cancer Institute.

“Someone asked me, is this ready for primetime?” he said. “My feeling is that this study gives doctors and patients permission to use aromatase inhibitors, and specifically exemestane, to lower a woman’s risk of breast cancer, so in that sense it’s ready for primetime. But I don’t think it’s a show that many women are going to decide to come to. It is there, but most people are not going to turn on their TVs.”

The positive findings on exemestane were expected, given previous findings on the success that it and other drugs like it had already shown in decreasing the risk of a recurrence of breast cancer, he said.

“The real question is, is it worth the side effects? How much is the benefit and is it worth taking it? To answer that, it very much depends on the individual woman, both in terms of her preferences but maybe more importantly than that, her level of risk of developing breast cancer.”

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Is it time to put exemestane in the drinking water? No.

[/module]Eric pointed out that the study did find that exemestane reduced a woman’s risk by about two-thirds, but it’s important to note that a typical 60-year-old woman’s risk of breast cancer is not very high. If you’re at average risk, meaning your risk is less than 1 in 100 for a given year, the drug may lower your risk to something like 1 in 300.

“But in order to achieve that, you have a lot of people take the drug who otherwise wouldn’t get breast cancer. Now, if you’re someone who can take exemestane and you have no side effects, maybe that’s worth it. But most women have some number of side effects, even if mild, from drugs we put them on, and some women who take drugs like aromatase inhibitors have significant side effects,” from arthritis to hot flashes.

Well, I asked, wouldn’t women tend to say, “I’ll try it, and see if I get side effects?”

“Some motivated women would say that,” Eric said. “There are women who are worried about breast cancer; they may know that they have an increased risk already, and ‘If I can lower my risk and have no side effects, I’ll take a pill a day.‘ I dont think that will be true of the typical 60-year-old with no risk factors. If you have a strong family history or a premalignant lesion that dramatically increases your chance of breast cancer, taking a drug like this may make a great deal of sense.”

A few of Eric's other caveats:
-It is not yet clear whether the preventive benefits of exemestane last even after a woman stops taking the drug, which has been shown for a similar drug, tamoxifen.
-It is not yet clear whether exemestane’s benefits translate into improved survival statistics. It’s possible that treating women with exemestane only after they get cancer — and sparing everybody else the side effects — would work just as well.
-Part of why statins are so popular is that their effects can be measured in the lipid levels in the blood. There is no such easy measure for exemestane’s effects.
-Exemestane is only for post-menopausal women, and only to prevent estrogen-receptor-positive breast cancer, so it does not address the problem of breast cancer in younger women, or aggressive cancers that are not sensitive to hormones.

For all those caveats, Eric said, he worries that there may be women who are at significantly heightened risk of breast cancer who really should take exemestane preventively, but whose doctors, non-oncologists, may not consider it.

On the other hand, he worries that exemestane may be oversold. “This isn’t for everyone,” he said.

So very roughly, I asked, what portion of postmenopausal women are good candidates for it?

“I think that this is probably something that should be considered seriously by 10-20% of postmenopausal women — maybe even 25%. I think that it’s really for women who are at increased risk, women who have a relative with breast cancer, women who have a premalignant finding, women who have a genetic predisposition.”

Ultimately, he said, the exemestane study is “both big news and not big news. It’s totally expected news. But I think it’s news that we needed before we started doing this on a widespread basis.”

Is it time to put exemestane in the drinking water? No.

But “I think what it does is that it provides another option to women who want to take a drug to prevent breast cancer, particularly women at high risk. And it emphasizes that we may be able to develop additional strategies that will lower risk in other ways.”