Proton therapy results in fewer side effects than traditional X-ray radiation therapy for many cancer patients, according to a new study led by Washington University School of Medicine and the Perelman School of Medicine at University of Pennsylvania. Even with reduced side effects, proton therapy resulted in cure rates similar to those of X-ray radiation therapy.
The findings will be presented next week by the study’s first author, Brian C. Baumann, MD, a radiation oncologist at Washington University School of Medicine, at the American Society of Clinical Oncology’s annual meeting, in Chicago.
The study is the first major side-by-side comparison of side effects related to proton therapy and X-ray radiation therapy. It included almost 1500 patients receiving combined chemotherapy and radiation therapy for lung, brain, head and neck, gastrointestinal and gynaecologic cancers that had not yet spread to other parts of the body. Such patients receive both radiation and chemotherapy, a treatment regimen that often cures nonmetastatic cancer. But it also causes severe side effects — such as difficulty swallowing, nausea and diarrhoea.
After controlling for differences between the groups, such as age and additional medical problems, the researchers found that patients receiving proton therapy experienced a two-thirds reduction in the relative risk of severe side effects within 90 days of treatment, compared with patients receiving X-ray radiation therapy. Forty-five of 391 patients receiving proton therapy experienced a severe side effect in the 90-day time frame (11.5%). In the X-ray radiation therapy group, 301 of 1092 patients experienced a severe side effect in the same period (27.6%). Patient data on side effects were gathered as the trial was ongoing, rather than after the fact.
“Proton therapy was associated with a substantial reduction in the rates of severe acute side effects — those that cause unplanned hospitalisations or trips to the emergency room — compared with conventional photon, or X-ray, radiation for patients treated with concurrent radiation and chemotherapy,” said Baumann, an assistant professor of radiation oncology at Washington University and an adjunct assistant professor of radiation oncology at Penn. “The opportunity to reduce the risk of severe side effects for patients and thereby improve their quality of life is very exciting to me. While there have been other studies suggesting that proton therapy may have fewer side effects, we were somewhat surprised by the large magnitude of the benefit.”
The researchers focused their study on what grade 3 adverse events, which are severe enough to require hospitalisation. These can include pain, difficulty swallowing that might result in weight loss, difficulty breathing, and nausea and diarrhea severe enough to cause dehydration.
The researchers also found no differences between the two groups in survival, suggesting that proton therapy was just as effective in treating the cancer even as it caused fewer side effects. Overall survival at one year for the proton therapy group was 83% of patients versus 81% for the X-ray radiation therapy group. This difference was not statistically significant.
This study is the first large review of data across several cancer types to show a reduced side-effect profile for proton therapy compared with X-ray radiation therapy for patients receiving combined chemotherapy and radiation.