Keller, Daniel M. PHD
As noted in the first part of this article in the March 25th issue, medical centers are continuing to build and open new hugely expensive proton beam radiation therapy (PBRT) facilities, even though there have been very few data to date from randomized controlled trials demonstrating better efficacy or lower adverse effects. For now, it is a somewhat “chicken and egg” situation: How many more proton beam facilities are needed and justified before the data are fully in, to generate the data on usefulness for the technique?
PROTON BEAM RT IMAGE...Image Tools
Real-time PET Scans: A Unique Advantage
Proton therapy leaves its “signature” in the body for some time as irradiated tissue emits gamma rays. Unlike traditional PET scans, no tracers need to be injected since the irradiated tissue itself will emit detectable gamma rays. Different isotopes (of carbon, nitrogen, or oxygen) have different half lives, on the order of minutes. Therefore, real-time positron emission tomographic (PET) scans are possible, but because of the relatively short half-lives, “seconds and minutes count,” explained Stephen Hahn, MD, Professor and Chief of the Department of Radiation Oncology at the University of Pennsylvania, home of the newly opened Roberts Proton Therapy Center, which was built using money from Penn Medicine, a large regional patient care, education, and research system.
“What's unique about our facility is that we are building an in-room PET scanner, so the patient can get treated and we scan right away, one or two minutes right after the treatment.”
An advantage of real-time PET scanning is that a clinician can assess the image to determine the radiation dose delivered to the tissue and compare it with the planned dose. In this way, subsequent doses and areas can be planned.
STEPHEN HAHN, MD We ...Image Tools
In an analysis of the cost effectiveness of proton beam radiation therapy for adenocarcinoma of the prostate published in 2007, Andre Konski, MD, et al (JCO 2007;25:3603-3608) concluded that even when considering the higher possible dose of protons compared with IMRT photons, PBRT was not cost effective for most patients with prostate cancer using the commonly accepted standard of $50,000 per quality-adjusted life year.
The authors recommended that “consideration should be given to limit the construction of proton facilities until data are available from properly designed trials to identify the role of proton therapy in the management of different malignancies.”
However, cost is a moving target, and Dr. Hahn predicted that costs will come down as clinicians learn how best to use the technology and treat with fewer fractions. Also, costs should decrease as the technology becomes more widespread.
Now being planned at his center is a randomized controlled trial of intensity-modulated radiation therapy (IMRT) vs protons for prostate cancer patients. The primary endpoint will be rectal symptoms, including proctitis, and the researchers will also look at bladder symptoms and erectile dysfunction.
Another endpoint, though, will be an economic analysis to be done in conjunction with researchers at the Leonard Davis Institute for Health Economics at Penn. “Although it's uncomfortable for all of us to talk about costs, it's a reality for us, and we have to sort of think about it,” Dr. Hahn said.
For the future, in-room, real-time PET scanning and other imaging is going to be a next step for PBRT. “That's going to help us individualize patient treatments,” he said.
Dr. Hahn said he also looks forward to “pencil beam” scanning—“where you have a very small spot size and you basically paint the dose [onto the target]. It makes it even more conformal to the tumor and less to the normal tissues.” Finally, the use of charged-particles other than protons, such as carbon, may be investigated although their use would require a different facility than for PBRT.
Medicine vs Marketing
With a very large investment in a PBRT facility, a medical center will have to keep it running at or near full capacity. Whereas major cancer centers can offer various radiation modalities as well as chemotherapies and biologic therapies under one roof, a concern arises over just how much the technology will be promoted, especially over other available therapies, and the concern may be especially acute if freestanding facilities are built that offer only PBRT.
Patients often want the newest technology, particularly when it is covered in the media or advertised by medical centers. Dr. Hahn said he believes that physicians need to manage patients' expectations and it would be unethical to be “selling treatment” to patients: “We have to say, ‘This is a new technology, we're learning how to use it, it has been proven for some diseases,'” he advised.
Proton therapy is not “an end unto itself,” in his estimation. “We really, truly want to do what's right for our patients, and so this absolutely cannot be a discussion about just protons. This can't be a discussion about an arms race,” Dr. Hahn emphasized. “This has to be a rational discussion about what's right for that individual patient when they come through the door in the context of their disease, their other side effects, and other treatments they've had.”
This series on PBRT will continue with several articles by Eric Rosenthal. Next up: Proton Beam Radiation Therapy: Balancing Evidence-Based Use with the Bottom Line
(In Part 1 of this article in the March 25th issue, the images were mistakenly combined, with just the caption for Figure 1 used. The correct versions for both appear here.)
© 2010 Lippincott Williams & Wilkins, Inc.