On the value of carbon-ion therapy

► Schulz replies: Let’s face reality. Radiation therapy is now entering its second century, and despite phenomenal gains in its technology, in many cases it still plays second fiddle to the surgeon’s scalpel. Its role is often crucial, but, like surgery, its impact on clinical outcomes is fast approaching a plateau beyond which future improvements in relative survival will be measured in single digits.

The most important technical advances in radiation therapy have dealt with the generation of dose distributions. The goal is to concentrate dose to the tumor while minimizing it to surrounding normal tissues, thus enhancing the therapeutic ratio and reducing treatment-induced morbidities. No doubt, beams of charged particles come closer to achieving that goal than do high-energy x rays; however, the differences are usually small and the results from x rays clinically acceptable.

The only way to prove that carbon-ion therapy (CIT) is superior to intensity-modulated radiation therapy (IMRT) is by rigorously controlled, randomized clinical trials that would take between 5 and 10 years to yield statistically significant results. Let’s suppose that for four or five of the most common cancers, CIT yields relative five-year survival rates that are 15% higher than those for IMRT. What do we do? There are perhaps a half million patients per year in the US. Let’s be optimistic and accept that each CIT facility can treat 5000 patients per year. One hundred CIT facilities would cost on the order of $20 billion and, even with the most favorable politics, take 10 years to assemble. That is a highly unrealistic scenario.

I am as intrigued as the next physicist by the gadgetry of particle-beam therapy, but cancer is a biological problem, and its ultimate cure will be provided by biologists and physicians with specific expertise in genetics, molecular biology, immunotherapy, and related fields. The pace of present-day research suggests that soon there will be other drug therapies; indeed, those currently in clinical trials are yielding promising results for pancreatic cancer and metastatic melanoma, two of the most deadly cancers. On the practical side, new drugs, as they are developed, can be readily provided to patients in all parts of our country. Whereas with CIT the patient has to travel to a center, with drug therapy the treatment can travel to the patient, without the pouring of a single ton of concrete or the precision machining of waveguides and superconducting magnets.