Research updates

These results were presented at the ASCO Annual Meeting in May 2026 and have not yet been published in full in a peer reviewed journal.

COMPPARE is a large national study comparing proton therapy with standard photon radiation therapy in prostate cancer. The early results cover two different follow up windows: two years for side effects such as bowel urgency, bowel frequency and other gastrointestinal toxicity, and three years for disease progression. Strong early outcomes were reported for both treatment approaches. The investigators note that follow up needs to continue before longer term questions can be answered, including disease control, late emerging side effects and the risk of secondary cancers. The study is funded by the Patient-Centered Outcomes Research Institute in the United States.

This study pooled seven separate research efforts comparing proton and photon radiation therapy in non-small cell lung cancer, bringing together data from more than 240,000 patients in a single analysis. Long term survival rates were similar between the two approaches. In the first year after treatment, however, patients who received proton therapy had higher odds of survival. The researchers link this difference to the reduced amount of radiation proton therapy delivers to the heart and to healthy lung tissue.

These results were presented at the ASTRO Annual Meeting in September 2025 and have not yet been published in full in a peer reviewed journal. The trial protocol has been published and is listed below.

RADCOMP is the first randomised phase 3 trial to directly compare proton and photon radiation therapy in breast cancer. More than a thousand patients with locally advanced breast cancer were randomly assigned to one of the two approaches. According to the results presented at the meeting, both treatments preserved quality of life across multiple dimensions, with preference measures favouring protons. The trial’s clinical chair noted that with contemporary techniques, curative doses of radiation can be delivered in a way that preserves several aspects of quality of life. Patients continue to be followed for cardiovascular outcomes and long term disease control.

Two sub-studies from within RADCOMP have been published in peer reviewed journals, covering thyroid function and the relationship between cardiac radiation dose and quality of life. Neither reports the trial’s main comparison.

Researchers at the University of Tsukuba in Japan retrospectively reviewed records for 189 patients under the age of 20 who received proton therapy for intracranial tumours at their centre between 1991 and 2023. Among the 151 patients with adequate follow up data, with a median follow up of 41.7 months, the five year cumulative incidence of brain necrosis was 2.3 percent and the incidence of intracranial secondary cancer was 2.7 percent. In the 125 patients who received proton therapy alone, those figures were 1.7 percent and 3.6 percent respectively. The authors concluded that these findings point to a favourable long term safety profile in this group of patients. This is not a randomised trial but a retrospective record review from a single centre.

This systematic review screened 75 articles published between 2019 and 2024 on the long term cognitive and behavioural outcomes of children who received radiation therapy for brain tumours, and analysed the 14 studies that met its criteria. Children treated with proton radiation therapy showed better neurocognitive and academic outcomes than those treated with photon radiation therapy. The review also found that cognitive abilities can be affected regardless of the treatment method, with the risk being most persistent in children who receive radiation therapy at a very young age. The rationale for using proton therapy in paediatric brain tumours rests on reducing the dose delivered to regions such as the hippocampus, which is critical to memory.

This randomised trial, conducted at Loma Linda University, compared proton therapy with transarterial chemoembolisation, known as TACE, in previously untreated hepatocellular carcinoma patients who met transplant criteria. Thirty six patients were assigned to proton therapy and 40 to TACE. Proton therapy was delivered as a total of 70.2 Gy over 15 sessions across three weeks, while TACE was repeated until a complete or maximal response was achieved. At two years, overall survival was similar between the groups, at 68 percent and 65 percent. The time patients went without disease progression was longer in the proton group. The study also includes a comparison of toxicity and cost.

In this phase 2B trial at MD Anderson, 145 patients with locally advanced esophageal cancer were randomised to proton therapy or IMRT. One of the measures was total toxicity burden, a single score combining 11 different side effects and surgical complications experienced by the patient over the year following treatment. At interim analysis, the probability that this score was lower in the proton arm reached 0.9989, crossing the pre-specified stopping boundary. The difference was most pronounced among patients who underwent surgery, where the rate of post-operative complications was markedly lower in the proton group. Survival was the same in both arms: three year progression free survival was 50.8 percent with IMRT and 51.2 percent with proton therapy, and three year overall survival was 44.5 percent in each arm. This is regarded as the first randomised trial to show an advantage for proton therapy over photon therapy in a specific cancer.

This phase 2 trial at Massachusetts General Hospital enrolled 59 patients aged 3 to 21 diagnosed with medulloblastoma between 2003 and 2009, with a median follow up of seven years among surviving patients. The results showed that proton radiation therapy produced survival outcomes similar to conventional photon radiation therapy, with an acceptable toxicity profile. According to the lead investigator, proton therapy maintained high cure rates while reducing long term side effects, particularly in hearing and neurocognitive function, and eliminated effects on the heart, lungs, gastrointestinal system and reproductive system. That last group of side effects comes from the dose a photon beam deposits as it exits the body, and does not occur with proton therapy because the proton beam stops at the tumour.