Proton therapy may serve as a viable alternative for patients with intractable liver cancer who cannot receive standard treatment, according to new research findings.
A research team led by Professors Park Hee-chul and Yu Jeong-il from the Department of Radiation Oncology at Samsung Seoul Hospital announced Wednesday that they have published an analysis of 2,000 proton therapy cases for liver cancer in the European Journal of Cancer.
Samsung Seoul Hospital became the first private medical institution in Korea to introduce proton therapy equipment in late 2015 and became the first in the country to surpass 2,000 proton therapy cases for liver cancer in September 2024. The study encompasses nearly a decade of treatment results from 1,823 liver cancer patients, including those who received multiple treatments.
All patients analyzed were those for whom standard treatments such as surgery or radiofrequency ablation were impossible or unsuitable according to the Barcelona Clinic Liver Cancer (BCLC) staging system, the international guideline. These patients had essentially fallen into a treatment blind spot due to tumor location, liver function, underlying conditions, or advanced age. The study included patients across various stages, from very early BCLC stage 0 through stages A, B, and C.
Proton therapy is a cutting-edge radiation treatment that destroys cancer cells by accelerating protons—the nuclei of hydrogen atoms—to approximately 60% the speed of light and directing them into the patient's body. Like heavy ion therapy, it utilizes the Bragg peak phenomenon, where accelerated particle beams release energy and disappear at the moment they strike cancer cells inside the body. This allows for precise targeting of cancerous tissue while minimizing impact on surrounding normal tissue. However, highly advanced techniques are essential to maximize treatment effectiveness.
Samsung Seoul Hospital enhanced precision based on its experience with X-ray-based liver cancer radiation therapy, including respiratory gating technology. Before treatment, 4D specialized CT scans are taken to understand how the cancer and organs move during breathing. During treatment, real-time respiratory status is monitored, and protons are delivered only during consistent breathing cycles.
The results showed favorable outcomes not only for early-stage liver cancer but also for considerably advanced stages. The two-year local progression-free rate—the percentage of targeted tumors that did not recur or progress—was 95.5% for BCLC stage 0, maintaining high levels at 93.9% for stage A, 98.5% for stage B, and 87.6% for stage C. When the follow-up period was extended to three years, favorable outcomes continued with 91.1% for BCLC stage 0, 91.3% for stage A, 95.0% for stage B, and 83.3% for stage C. Overall survival rates at three years—the most important indicator for evaluating cancer treatment outcomes—were 81.1% for BCLC stage 0, 65.5% for stage A, 45.5% for stage B, and 37.2% for stage C. The researchers noted that meaningful treatment outcomes were achieved even in patient groups with considerably advanced liver cancer.
The research team attributed these excellent results to the multidisciplinary collaboration system. Through multidisciplinary care involving specialists from gastroenterology, surgery, radiology, hematology-oncology, radiation oncology, and pathology, appropriate patient groups were selected, and accumulated experience in liver cancer radiation therapy was integrated to establish proton therapy protocols. Recently, the team has been accelerating research on FLASH technology, which delivers high-dose radiation of over 40 Gray (Gy) per second in ultra-short bursts of less than one second.
"This study was possible thanks to building the largest single-center cohort through standardized multidisciplinary collaboration and proton therapy protocols," Professor Yu said. "Within a liver cancer center system with abundant treatment experience, proton therapy will be a key to improving patient prognosis."
Professor Park Hee-chul, who heads the Proton Therapy Center, said, "Proton therapy has become a definitive treatment alternative that can offer high local control rates and survival rates for liver cancer patients unsuitable for conventional treatment. Its role is expected to expand further through prospective studies."
As of 2025, Samsung Seoul Hospital's Proton Therapy Center has treated more than 8,183 patients in total, with treatment sessions exceeding 100,000. Among the 7,908 patients treated through September 2025, liver cancer patients numbered 2,403—the largest group—followed by 1,466 head and neck cancer patients, 1,304 lung cancer patients, 676 brain tumor patients, and 377 pancreaticobiliary cancer patients.
