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Promising Breast Cancer Treatment Averts ‘Collateral Damage’ to Healthy Cells

June 5, 2012 at 12:00 AM EST
Doctors meeting this week at a major conference in Chicago believe they are on track to create a drug that would specifically target cancer cells, while largely leaving healthy cells undamaged. Gwen Ifill and Dr. Michael Link of the American Society of Clinical Oncology discuss the findings.
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GWEN IFILL: Now, new research in the battle against breast cancer that offers intriguing promise for tackling other cancers as well.

Doctors meeting at a major conference in Chicago this week believe they are on track to create a drug that would specifically target cancer cells, while largely leaving healthy cells undamaged.

For more about this and other findings, I am joined by Dr. Michael Link, the president of the American Society of Clinical Oncology, the group hosting this week’s conference. He’s a pediatric cancer specialist at Stanford University School of Medicine.

Welcome, Dr. Link.

So, tell me, how does this work exactly? How do you target the bad cells and not hurt the good ones?

DR. MICHAEL LINK, president, American Society of Clinical Oncology: Well, this is great technology because what we have is a molecule that homes in on a target that is on the cancer cells, but not on very many normal cells.

And attached to that molecule is a poison or a toxin which is delivered directly to the cell. And then the cell sort of takes it in. And then that toxin or poison is activated and the cell is destroyed. And because it’s only delivered to the cancer cell, we minimize the collateral damage of the normal cells that are nearby.

GWEN IFILL: This would only — this has only been proven effective so far for recurrent cancers?

DR. MICHAEL LINK: Well, the drug has been tested in women who have cancers that have been refractory or have recurred.

The good news is that they have already had the antibody trastuzumab, which targets this same target on the surface of the cell. But now what we have done is we have souped up the molecule so it’s delivering a toxin, but getting at that same target and delivering that poison to the cell.

GWEN IFILL: You use the word poison, which raises the question of side effects. Are there great side effects in this kind of treatment?

DR. MICHAEL LINK: No. That’s the good news here, although there are some side effects.

But mostly, because the toxin is delivered directly to the cancer cell and because there’s specificity, meaning it doesn’t deliver that poison to normal cells which don’t have that target on their surface, most of the damage is done to the cancer cells without that collateral damage of the normal cells.

GWEN IFILL: So, how much does this increase the chances of prolonging survival?

DR. MICHAEL LINK: Well, in the study that we have seen, there’s not only a prolongation of the time for how long women stay without disease progression, but we already have a hint from this study, although it’s not final yet, that it’s prolonging the survival as well.

Now, these are women that have already had progression of their cancers despite treatment. The hope is, of course, is that this treatment will move earlier on in therapy to women who have not yet had recurrence of their disease on treatment and will be much more effective, as it usually is in patients with what we call earlier stage of their disease.

GWEN IFILL: So, let’s be clear. This is about delaying the worsening of a cancer, not eradicating it?

DR. MICHAEL LINK: Well, in the setting that it was used, which is often the case in the early testing of a drug, that is exactly the case, although the survival is prolonged.

And what we see from this study is that the median survival, in other words, how long half the women are still alive, has not yet been reached in the group of women that receive this. And we already know that it’s better than the standard treatment that would be normally used for women in this clinical situation.

So the hope is though, by applying it earlier on in treatment for women whose disease is not so refractory, that will be a time when we will really see the effectiveness of this drug.

GWEN IFILL: You came out with several reports out of this meeting this weekend. Another one, which was the news wasn’t as good, was a report that you came up — out with about childhood radiation and the long-term effect of that.

Can you tell me a little bit about that?

DR. MICHAEL LINK: Yes.

This is a message which, of course, is a mixed message really. What we’re finding out is that young women who are treated as young women, when they grow up and 20 years later and 30 years later, there’s a much higher incidence of breast cancer in those of them that have had radiation to the breast tissue during their childhood.

This is something that we worried about. But the news here is, it’s even women who have received a relatively low dose of irradiation. Now, the good news is, of course, that this is a testament to the fact that we have cured these women, that it’s 20 and 30 years after their cancer, and so that they are — really have survived their first cancer.

But this is something that, of course, the flip side or the bad news is that we have to worry about the price of cure. We have to worry about what are the late effects of our treatments that we give. And we owe it to the survivors to then make sure that we can do something about that treatment, perhaps to eliminate radiation from women who don’t need it, who we can actually treat them and cure them without the radiation. And we have precedent for that.

GWEN IFILL: You’re a pediatric cancer specialist. Someone comes to you with a child who is suffering from some version of childhood cancer, say non-Hodgkin’s lymphoma or something that is reasonably curable.

What do you tell the doctor? What should the doctor do to guard against bad effects later on in life?

DR. MICHAEL LINK: Well, we do our best.

And in the patients who have the best prognosis, particularly as an example that you cited in non-Hodgkin’s lymphoma, we have eliminated radiation for the treatment because we proved some years ago that we could do just as well with a little bit more chemotherapy, without the radiation, and eliminate that effect.

In some patients with more advanced diseases, we need to use radiation. Of course, the first — the first important goal is to cure the patient, because we won’t have these late side effects if we don’t cure the patient. But we do have an interest in survivors and what are the late effects of therapy, and that’s part of our commitment to the patient.

GWEN IFILL: Dr. Michael Link of Stanford University and president of the American Society of Clinical Oncology, thank you so much for helping us out.

DR. MICHAEL LINK: Thank you.