Ask Dr. Hallberg: Early cancer detection outpaces cancer differentiation

A new report found routine mammograms have led more than one million women to receive unnecessary breast cancer treatment.

Researchers reviewed three decades of mammogram data and found that nearly a third of all women diagnosed with breast cancer had tumors that would not have caused any symptoms. They concluded that breast cancer is often over-diagnosed and routine mammograms have "at best, only a small effect on the rate of death from breast cancer."

The report was published in the latest issue of the New England Journal of Medicine.

Dr. Jon Hallberg, MPR's medical analyst and medical director at the Mill City Clinic, discussed the report with MPR's Tom Crann this week. An edited transcript of the conversation is below.

Tom Crann: Let's get the basics first of this study. What did it show?

Dr. Jon Hallberg: The authors looked at mammograms that had been taken from 1976 to 2008, and during that time they found that on average we're detecting a lot more breast cancers, really early breast cancers, which is great. I mean that's one of the points of screening for cancer, especially cancer that might be fatal.

But it didn't seem to find a correlation with detecting severe cancers and therefore saving lives in that respect ... They think that we're catching a lot of early stuff really early, and frankly, cancers that may not have been fatal.

Crann: You're saying severe cancers, cancers that may not have been fatal — it sounds like you're making a distinction. Is it possible that when it comes to breast cancer and other cancers that all cancers aren't equal?

Hallberg: I think a few years ago we really weren't talking along these lines, but this is something that's becoming more and more obvious: that things like breast cancer, things like prostate cancer, there's probably a sub-set that maybe we shouldn't even be calling cancer because it doesn't behave the same way that cancers that can take our lives do.

And this is exciting in a way, but it also poses a big conundrum ... because right now we're still treating all of them in the same way for the most part.

Crann: And are we at a point where doctors or researchers can tell, 'Well, you know, this cancer is fatal. This one: maybe not?'

Hallberg: No, and that's sort of the Nobel Prize-winning question. I think that when someone figures out how do you detect (that) under a microscope or using certain techniques, you can figure out that, 'OK, this cancer is slow growing and frankly it's going to take decades and decades before it becomes an issue.' And, 'This one's really aggressive.'

Once we know that, my goodness, it's going to change how we do things in medicine a great deal.

Crann: Maybe this is simplistic, but isn't it better to be safe than sorry here?

Hallberg: Sure, and that's what a lot of people who I think are offended or bothered by the study, they're saying, 'Look, isn't this the whole point? We should be catching things as soon as possible.'

And indeed that's true, but I think that the trouble is then let's say that perhaps a third of women who have had these cancers diagnosed, and they've had biopsies, they know it's cancer, they would like to have a mastectomy or a bilateral mastectomy. That's surgery. They may have reconstruction. That's surgery. It's painful. It's expensive. It may cause infections. It may cause all kinds of problems.

The same is true with men getting their prostates taken out. I mean these are not simple procedures, and I think that between morbidity, disease, or problems that come about from having surgery, to cost, to pain, there's a lot of pieces to be factored in. If we didn't have to do all of this, my goodness, it would save a lot of suffering, and money, of course.

Crann: This is not exactly new thinking because you and I have talked about this when it comes to prostate cancer, but it is indeed controversial, especially that sort of wait and see approach.

Hallberg: Right, and nobody wants to wait and see. And that's the trouble we have. In primary care, I don't really deal with that so much because this is really a conversation someone has with an oncologist, for example. 'Here are the options. Here's what we seem to know about this.'

People are having really, really good conversations, but still it ultimately comes down to the fact that most patients are saying, 'Look, you're telling me that I have cancer. I want it treated. I want it taken out. I want it aggressively taken care of. I'm not willing to watch and wait, and wait and see.'

Crann: Practically, in the clinic, what will this mean when it comes to treatment or even recommendations for screening?

Hallberg: I don't think this is going to have any bearing whatsoever right now because it's not that kind of study. I think this information is the sort of thing that people at a higher policy level will be taking into account.

Crann: What does the study say about the future of cancer research and treatment?

Hallberg: I think it's very exciting. The controversy aside, if we get past that, what it's telling us is that we're doing a terrific job of detecting cancer early. And this is true across a lot of different cancers, but we may be too good at that because we haven't figured out yet how to differentiate between the cancers and know which way they're going to go, are they aggressive or not aggressive, and that's really the future I think of a lot of cancer research.

Interview edited and transcribed by MPR reporter Madeleine Baran.

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