Is spending on proton beam therapy for cancer going too far, too fast?

Who benefits?

So what is the evidence for and against the treatment? The theory is that proton beams target cancerous tissue more exactly. By accelerating subatomic particles towards the speed of light and concentrating them in a beam, proton treatment is thought to target cancerous tissue more precisely, minimising harm to healthy tissue while reducing side effects and increasing cure rates.

It has been shown to be beneficial and cost effective for treating children, whose tissue can be highly sensitive to stray radiation, and for certain uncommon brain cancers.

Using protons on childhood medulloblastoma may save €23 600 per patient, causing less damage to the brain and to growth hormone production.3 Benefits have also been found for skull base chordoma.4

But proton accelerators, especially in the US, are being marketed as treatment for prostate cancer rather than just childhood cancers, partly because the greater numbers of patients makes the financial returns better.

Not only is the benefit unclear in prostate cancer, but the side effects appear, in some cases, to be no better than for conventional radiotherapy, which undermines one of proton therapy’s selling points. In June 2011, a study of radiation therapy for prostate cancer found that patients receiving conventional radiation experienced fewer gastrointestinal problems than a similar group exposed to proton beams.5

“Somewhat surprisingly, proton therapy had the highest GI toxicity of the radiation modalities,” the authors noted.

Signs that proton beam therapy is less cost effective than conventional radiation for prostate cancer have been increasingly evident since 2007. In a study funded by the National Institutes of Health researchers calculated mean costs of around $64 000 for men in their 60s and 70s—significantly higher than the $39 000 for intensity modulated radiation therapy.6

“New treatments are introduced routinely into clinical practice without rigorous economic analysis,” noted the study’s authors. They urged “limiting the number of proton facilities” before more comprehensive analyses are done.

Despite the huge amount of money sunk into building accelerators, the first randomised controlled trial comparing x rays with proton beams is only just about to begin. That research, involving 400 patients and sponsored by the US National Cancer Institute at Massachusetts General in Boston and the University of Pennsylvania in Philadelphia, won’t be completed for seven years.

Harvard Medical School radiation oncologist Anthony Zietmen told the BMJ: “We rush into treatments before they are proved. Sometimes people are later found to have been harmed.” Zietman, who is involved in the Massachusetts General trial, added: “I don’t think we’re doing harm (with proton therapy), but we don’t know. In some instances, proton therapy might be inferior to existing treatments, and the quality of life might not be as good.

Robert Foote, a radiation oncologist at the Mayo Clinic who is overseeing a $370m project that will bring accelerators to new centres in Minnesota and Arizona within the next four years, is also worried that some centres are adopting the proton beam therapy before enough research has been done and, possibly, for the wrong indications.

He worries that some centres with big commercial investors will be keen to recoup their investment fast by putting through a large volume of patients, especially with prostate cancer, rather than using the technology for those most likely to benefit, such as children, a focus at the non-profit Mayo Clinic.

Foote says that two models of proton care have emerged in the US: “one to make money—the other to provide the best care possible for the people who need it.”