Proton Beam Therapy: evaluating claims in ASTRO papers of “excellent” quality of life data

Last week, the American Society for Radiation Oncology’s annual conference was held in Boston, and several papers were presented on proton beam therapy, and several medical centers sent out news releases about their involvement in the work.  MD Anderson Cancer Center in Houston  and Loma Linda University Medical Center in California were two that we saw.

I asked one of our HealthNewsReview.org story reviewers, Richard Hoffman, MD, MPH,  to review the claims. Here’s what he wrote:

———————————————

by Richard Hoffman, MD, MPH

Sometimes proton beam therapy seems to be an expensive cure in search of a disease.  While the $100+ million technology is considered an optimal therapy for tumors of the eye, brain, spinal cord, and pediatric solid tumors, much of the patient volume—and marketing—is for treating localized prostate cancer.   Unfortunately, we don’t know whether localized prostate cancers are best treated with proton beam, other radiotherapies, or surgery.  We are certain that a substantial proportion of localized prostate cancers are low-risk for progression and may well not require any active treatment.  Because so many indolent cancers are being found by PSA screening, one of the oft-touted metrics of treatment success—5-year cancer survival—is meaningless because essentially all of these men would survive without any treatment (or even with laetrile).

Ongoing randomized trials are comparing surgery vs. radiotherapy and different forms of radiotherapy.  The primary outcome is prostate cancer mortality, and these studies will provide the most definitive evidence for comparative treatment efficacy.  In the meantime, investigators have compared different radiation modalities for the surrogate endpoint of biochemical failure (rising PSA) and complication risks.  The Agency for Healthcare Research and Quality published a comparative evaluation of radiation treatments last year in Annals of Internal Medicine and found no high-quality survival data.  A recent systematic review in JAMA concluded that there was no significant difference in risks for urinary diagnoses or erectile dysfunction between proton beam therapy and intensity-modulated radiation therapy, though proton-therapy treated patients were more likely to be diagnosed with gastrointestinal problems.

Last week an abstract presented at the American Society of Radiation Oncology was touted here and here as showing “excellent” quality-of-life for prostate cancer patients treated with proton therapy.  (You can look it up at this link – but you have to track down paper #3139.) My review of the abstract was less enthusiastic.  Investigators reported comparable urinary and bowel functions (though not sexual function, which was adversely affected) between over 1000 prostate cancer patients treated with proton therapy and 112 “healthy” men of the same median age who had never had cancer.  In making this comparison, investigators evaluated their entire proton therapy cohort, including subjects from 5 different treatment centers who varied by tumor aggressiveness, age, and years of follow up.  Given that age at treatment, baseline function, receipt of adjuvant hormone therapy (provided for aggressive cancers), baseline function, and time from treatment all affect quality-of-life measurements, the primary study findings have little clinical relevance.  Secondary analyses determined that the differences in sexual function were due to some of these factors.  Finally, the response rate is not reported, raising concern for selection bias if the healthiest and most functional patients were most likely to answer the surveys.   Regardless, the study could not answer the questions of whether treatment was necessary or whether alternative radiotherapies would have been safer.

——————–

Publisher’s Note:  One of the places where proton beam therapy is being introduced – not just once, but twice – is Oklahoma City.  The Oklahoman newspaper reports, “Oklahoma City is future home for two proton therapy centers.”

The story refers to “a medical arms race” and hospital competition.  It refers to the research presented at the American Society for Radiation Oncology meeting and quotes Dr. Anthony Zietman, the immediate past chairman of the organization:

“But this wasn’t a randomized trial, often referred to as the gold standard in research, and it is being overspun, Zietman said.

What the research suggests is what most research related to proton therapy has suggested — proton therapy likely provides the same, or similar, benefits than other traditional, less expensive forms of radiation, Zietman said.

“No one is saying proton beam is bad treatment — proton beam is good,” Zietman said. “The question is — does it offer value? And this is where Sameer Keole is right — If protons were cheaper, we wouldn’t be having this discussion.”

The newspaper also posted an online video with the story, which doesn’t include any of the attempts at balance that appeared in the newspaper story.