'Proton therapy more effective than heavy particle therapy in preventing cancer recurrence'

A meta-analysis of the therapeutic effects of the two state-of-the-art radiation therapies showed no differences between proton therapy and heavy particle therapy in major treatment performances, including the survival rate of cancer patients.

However, proton therapy has proved more effective in preventing cancer recurrence than heavy particle therapy, according to a recent study, the first of its kind in Korea.

Samsung Medical Center (SMC) said Tuesday that a collaborative research team has conducted a meta-analysis of the effectiveness and safety of proton and heavy particle therapy and released its results.

Researchers who conducted the study included Professors Park Hee-chul and Lee Tae-hoon of the Department of Radiation Oncology at SMC, Professor Yoo Gyu-sang of the Department of Radiation Oncology at Chungbuk National University Hospital, Professor Kim Kang-pyo of the Department of Radiation Oncology at Jeju National University Hospital, and Professor Jang Jeong-yun of the Department of Radiation Oncology at Konkuk University Medical Center, along with researchers from the National Cancer Center in Singapore, the National Cancer Center in Japan, and the Proton Therapy Center at Chang Gung Memorial Hospital in Taiwan.

Meta-analysis is a research method that synthesizes and reviews multiple studies on a specific topic according to a certain systematic approach. It has the advantage of expanding the understanding of the topic by examining multiple studies and identifying recent trends.

According to the research team, 18 studies were selected from 3,983 articles on proton therapy and heavy particle therapy published until June 2023. These articles included the necessary patient definitions, treatment methods, differences between methods, and treatment outcomes for meta-analysis. In the papers analyzed by the researchers, 947 patients were treated with proton therapy, and 910 patients were treated with particle therapy.

Four radiation oncologists carefully reviewed each study and found that protons more effectively controlled tumors locally than heavy particles. However, there were no statistically significant differences in overall survival (OS), progression-free survival (PFS), or side effects, another measure of treatment success, between the two treatments.

Local control is the absence of cancer recurrence in the treated area. In the study, the risk of cancer returning to the treated area with protons was 31 percent lower than that of heavy particles. The same was true when subanalyzed by cancer type, the researchers said.

The results were attributed to the fact that both treatments have something in common: particle ray therapy. Characterized by a "Bragg peak," particle beams are protons, or heavy particles accelerated to a certain speed that release energy and dissipate as soon as they hit cancer cells in the body. This is why particle beam therapy is expected to minimize the impact on normal tissues other than cancer cells.

However, unlike hydrogen-based protons, carbon-based heavy particles can deliver more energy but are heavier, making it difficult to control the residual dose after hitting the cancer.

Proton therapy, on the other hand, is well-proven to be both safe and reliable, with more than 250,000 people receiving it worldwide as of 2019.

The study's outcomes and side effects were predictable due to the large number of previous studies. However, heavy particle therapy is still in its infancy, and there is insufficient data for meta-analysis.

"There are not many countries that have introduced heavy particle therapy, and there is no standardized treatment model accepted worldwide, so further research is needed to make an accurate comparison with protons," Professor Yoo said.

Professor Park said, "Both treatments have their uses for patients. We will identify the right treatment model through further research, as choosing the right treatment for the patient's condition is more important than the treatment itself."