PBRT vs. IMRT — another update

An article in yesterday’s Philadelphia Inquirer looked further into the question of the role of proton beam radiation therapy (PBRT) as a treatment for localized prostate cancer.

One of the key points emphasized in the article is that reductions in insurance coverage for PBRT appear to have been impacting the ability to enroll patients and conduct the very trial needed to actually demonstrate whether PBRT is or is not either more effective or equally effective but safer than photon-based intensity-modulated radiation therapy (IMRT) in the treatment of prostate cancer. However, the trial’s lead investigators seem to have found a way to overcome that problem by asking insurers to cover the costs for IMRT at parity to the costs for comparative IMRT if patients are enrolled in the trial (which seems like a very reasonable compromise for all concerned).

The “New” Prostate Cancer InfoLink would continue to encourage newly diagnosed patients who are considering external beam radiation therapy as a treatment for localized prostate cancer to think about enrolling in this trial. It will help us to resolve, once and for all, whether PBRT really is “better” than modern IMRT as a treatment for localized prostate cancer. At present patients can be enrolled in this trial at the University of Pennsylvania (in Philadelphia) or at Massachusetts General Hospital (in Boston), but more proton therapy centers are expected to start enrolling patients in this trial soon.

7 Responses


    I noticed the official trial description did not address protocol details for either imaging during treatment, though all will have a pelvic CT scan to plan treatment. There is no exclusion criterion for additional imaging, such as multiparametric MRI, etc., or for imaging during or between sessions. Imaging to support treatment has proven a major advance in recent years.

    There is also no protocol for patient/prostate positioning or real-time beam compensation based on imaging.

    There is no protocol for controlling lifestyle tactics or advice about such tactics. This study will likely be accruing for several years, during which time some tactics may surge in popularity. For instance, a fourth trial outcome favoring quality pomegranate juice or extract might move many patients in the trial to start consuming the juice or extract pills.

    Also, the trial description does not mention stratification by Gleason score or PSA, though all patients will be at stage T2b or lower, Gleason 4 + 3 = 7 or lower, and PSA < 20. I'm thinking having a large number of randomized patients should even things out, but is this a concern with 400 patients?

    Is there a basis to trust that variations in these areas will not be potentially significant sources of confounding?

    All this said, I'm glad this trial is ongoing.

  2. Jim:

    What you see on any trial protocol on ClinicalTrials.gov is a brief summary of the protocol, not the entire protocol. My understanding from the principal investigator is that there had to be some flexibility in the protocol to allow for the fact that there is no one defined consensus on “the best” way to carry out either IMRT or PBRT today and so there is some “site to site” flexibility but that the protocol to be used by each site must conform to some generally agreed principles and each site protocol must be approved by the trial monitoring group as and when each new site somes aboard.

    I am not worried by this given the stature of the investigators, and I have confidence that the study will meet very reasonable criteria for study quality.

    The inclusion of things like taking pomegranate juice or not is entirely up to the individual patients and their doctors because the investigators do not believe that such factors would affect the trial results one way or another … and I tend to agree with this.

  3. Thanks so much for the update. Unfortunately as the proof increases so does the advertising and these guys have some deep pockets.

    God Bless

  4. Why do insurers do this? On the one hand a lot of money and effort is being invested in building PBRT facilities, certainly in northern Europe. Yet insurers are reluctant to support patients. I don’t get it. What are their reasons? There was an “interesting” case of this conflict in the UK a week or so ago, but I cannot evaluate it. It did not concern prostate cancer, but, I think, a form of spinal cancer. And it concerned use of PBRT, not investment in new facilities. But surely, if PBRT was a reasonable option in this case, the result would increase our understanding of PBRT, as the option actually offered included some form of EBRT.

  5. Dear George:

    What we have here is a classic case of a very expensive form of treatment and its differing values in the treatment of rare as opposed to common forms of disorder.

    Most of the proton centers being built in Europe are not being built with the goal of treating things like prostate cancer. And I am sure that most of the proton centers being built in Europe are not being built with the goal of making a profit on their use. Having said that, I was absolutely barraged by innumerable media releases from the PBRT center treating the child from the UK that you referred to. As I understand it, there are currently plans to build two PBRT centers in the UK and it is thought that this will be sufficient to effectively treat those who really need this type of therapy in a population of about 70 million.

    By contrast, there are already 14 functioning PBRT centers in the USA and another 12 under development (that’s 26 centers for a population of 300 million; you do the math). Most of these centers in the USA think they will be able to make most of the necessary (for profit) revenue from treating things like breast cancer and prostate cancer — where the relative benefit compared to modern forms of external beam radiation therapy is unproven. It is not in the slightest bit surprising to me that the commercial insurance industry is balking. At present I can see no justification for paying any more for PBRT than for the sophisticated forms of IMRT that are now available. If the PBRT industry can prove that it really is “better”, then one might reconsider.

  6. Thanks for your response and comments, Sitemaster.

  7. Dear Sitemaster,

    Thanks for clearing that up. I did not know that there were so many PBRT centers in the USA, while the non-inferiority of PBRT compared with IMRT has not been verified. In this case I cannot blame the insurers. Any purely State-run scheme would most likely react similarly.

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