Radiation therapy is a key pillar of cancer treatment, a way to kill tumours before they kill using a beam tightly targeted at the site of danger. Nevertheless, the side effects can be traumatic. Radiation comes in many varieties, however, and the choice of photons over protons may be causing a lot of unnecessary damage.
Ionizing radiation strips electrons off atoms and can damage DNA, leading to cell death – disastrous most of the time, but a way to stop cancers reproducing. By far the most common method uses X-rays, with the energetic photons delivered via beams arriving at different angles to meet right at the tumour.
Unfortunately, electromagnetic radiation that powerful doesn’t always stop neatly on cue, so some of the photons penetrate further into the body, damaging surrounding tissues. An alternative option is to use protons (positively charged subatomic particles), which overshoot much less within the body. Dr Brian Baumann of the University of Pennsylvania, USA, compared the two forms of radiation.
In JAMA Oncology Baumann reports the two score equally for cancer elimination and overall survival, but when it comes to side effects the outcomes are very different. In a group of 1,483 cancer patients who received both radiation and chemotherapy, the 391 who were zapped with protons had a third the risk of severe toxicity as those who got the traditional electromagnetic treatment, allowing for differences in age and other risk factors.
With consequences including nausea, diarrhea, and difficulty swallowing or breathing often so severe patients were hospitalized, the side effects are no minor issue. Naturally, intense pain was a frequent feature. Such a large reduction means the avoidance of enormous suffering and substantial cost.
The sample included a wide variety of cancer types, suggesting protons don’t just beat photons in niche cases.
“This is exciting because it shows that proton therapy offers a way for us to reduce the serious side effects of chemo-radiation and improve patient health and wellbeing without sacrificing the effectiveness of the therapy,” Baumann said in a statement. Protons were expected to be less damaging, but the ratio shocked the researchers.
When medical trials reveal a treatment’s worth, particularly for cancer, there is usually a wait of many years before anything gets approved for widespread use. However, proton radiation is already FDA-approved, having been trialed as far back as 1957. Its application has been restricted to niche cases such as certain rare cancers known to respond well to higher radiation doses.
The reason proton radiotherapy has been left in its X-ray counterpart’s shade is cost, although the price gap is closing. Moreover, weighed against the costs of treating side effects – or even people avoiding treatment for fear of the effects – that could be a very false economy, yet one that has been surprisingly unquestioned.