103 Issue 10 Kachnic Transcript
Kristine Crane: According to a JNCI study, IMRT, or intensity modulated radiation therapy, is on the rise for treating breast cancer. IMRT is more precise and less toxic than standard radiation therapy, but it's also more expensive, too expensive, according to some experts. I talked with Dr. Lisa Kachnic of Boston University, who co-authored an editorial on the IMRT study. You wrote this review about IMRT, intensity modulated radiation therapy. So why don't we just start very simply, and if you could tell us what that is and how it differs from standard radiation therapy.
Lisa Kachnic: Oh, sure. So IMRT is a more novel radiation delivery technology, and what it does is it modulates the beams of radiation so that you can effectively paint the dose of radiation to your target, or tumor, and minimize the dose of radiation to the normal surrounding structures. And this is in contrast to two or three-dimensional radiation, which does not offer that technology and really bases treatment on either bony anatomy for two-dimension radiation and 3-D anatomy for three-dimensional radiation. But the only thing that three-dimensional radiation offers is knowledge of the dose that goes to your tumor and the normal tissues, but you don't have the ability to really spare the normal tissues like you do with IMRT.
Kristine Crane: So how does it effectively spare the surrounding tissue?
Lisa Kachnic: Because if we modulate the beams of radiation, we can sort of, as I said-- the sort of laymen's terms of saying it is paint the dose to the tumor and sort of minimize the dose to the normal surrounding structures, whereas in 2D and 3D, the normal structures effectively get similar doses to the tumor.
Kristine Crane: So what percentage of patients get IMRT?
Lisa Kachnic: I think nowadays probably about 40% to 50% of our patients get IMRT but not for breast cancer, for just a variety of other tumors, such as head and neck and prostate are the two most frequent ones.
Kristine Crane: But this particular review looked at?
Lisa Kachnic: This one was on breast. So for breast cancer, the rate of using IMRT is not high, and then this was also documented in the article, too, although it's gone really from sort of a zero level-- I think in the article is about 11%.
Kristine Crane: So what are the particular challenges to using it in the breast compared to other organs?
Lisa Kachnic: For early-stage breast cancer, which this article depicted, I'm not convinced that using IMRT is cost effective. There are sort of ramped-up three-dimensional treatment plans that you can do, adding a few segments of IMRT exposure that may be able to provide sort of the same equal distribution of dose that we get with IMRT using 3D. I'm not really sure of the need for IMRT for all early-stage breast cancers. There may be some that IMRT may produce a better plan, but it's not everyone. Now, for more advanced-stage breast cancer, which this article does not address, I think that IMRT may be advantageous, but we don't have the evidence-based literature to sort of prove that yet.
Kristine Crane: So does that mean for like even metastatic breast cancer that's in the liver or even the brain?
Lisa Kachnic: Usually for palliation. We don't often use IMRT for locally advanced breast cancer, where the tumor has spread from the breast to the regional axillary and other lymph nodes. And IMRT may also be advantageous when there's an issue of normal tissue sparing, so it may be for some early-stage breast cancers, some women may have particular anatomy where the lung and the heart would get significant dose with the radiation three-dimensional fields. So in that instance, IMRT may be advantageous, too.
Kristine Crane: So what do you attribute the 10-fold increase to?
Lisa Kachnic: We think that this change was driven by what pays but not necessarily by what improves patient care.
Kristine Crane: So it's basically going to people where they're reimbursed?
Lisa Kachnic: Yes, exactly. It increased in areas of the country where it was reimbursed.
Kristine Crane: Because it's quite expensive?
Lisa Kachnic: Yeah, it's more expensive than three-dimensional. I wouldn't say it's like double-expensive, but I think it's about 30% more.
Kristine Crane: And so on a clinical level, apart from what you've already said about sparing the surrounding tissue, what would be the other advantages of using this?
Lisa Kachnic: So I mean there is sort of two different advantages. So for early-stage disease, which is what the article addressed, there actually has been some randomized trials showing that IMRT improves acute toxicity and breast cosmesis over and beyond two or three-dimensional radiation, and the reason for that is a little bit different than the normal tissue sparing. It has to do-- the acute toxicity they're referring to is skin, or dermatitis. So what happens with three-dimensional radiation, typically about a third or so of the women will notice some marked skin irritation typically in the area underneath the breast, which is referred to as the inframammary fold. And the reason for that with 3D is because the dose isn't always so homogeneic. We get hot and cold spots with the radiation, so some areas of the breast will have sort of a hotter radiation dose to it, and some may get cold. And so what happens is in that area under the breast, we typically get a hot spot, and that's what causes that skin irritation. So with IMRT, you can kind of even the dose out and make it homogeneic throughout the breast, which is just another word for evening out, so that we don't get as much of that skin irritation underneath the breast. But what we had said in the editorial was, yes, we appreciate that, but you can probably do that without sort of full-blown IMRT. You can kind of just put a few little segments of IMRT into your 3D field and achieve the same result.
Kristine Crane: So all things being equal in terms of reimbursement, which I know it's not throughout the country, but what would be the sort of most useful application of this?
Lisa Kachnic: So we think the most useful application for sort of inverse planning, which is the full-blown inverse planning IMRT, is for women that need coverage of their elective nodal groups with their breast or chest or for left-sided breast cancers where the lung and the heart may become an issue with three-dimensional radiation because many times on the left side, we still don't really get that much lung and heart in our field with 3D, but with some cases, due to the patient's anatomy, it becomes an issue, and those patients' IMRT may have a normal tissue-sparing effect. But I think for the whole breast, which was the purpose of this series article, and the three randomized trials were also just looking at breast, I'm not sure that IMRT is the way to go in terms of cost-effectiveness when we can do sort of that quick-and-dirty 3D with a few IMRT segments, which probably achieves the same results. We don't have a trial to show that, but it's likely that it would produce the same results.
Kristine Crane: And so what do you think is the future of IMRT?
Lisa Kachnic: So for breast, my guess is we're not going to see any further increase in the use of IMRT for whole breast cancer. I mean for breast only. But perhaps after more data is collected, we might see the use of IMRT slightly increased for those that need elective nodal coverage, especially for the left-sided tumors that need elective nodal coverage and for patients that have challenging anatomy.
Kristine Crane: That was Dr. Lisa Kachnic, the Chief of Radiation at Boston University School of Medicine. For a transcript of this interview or to listen to other JNCI podcasts, please visit our website at JNCI.OxfordJournals.org. This is Kristine Crane. Thank you for listening.
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