"Dr. Grassberger has led a study examining in detail dosimetric properties of proton versus photon radiotherapy for liver cancer using the same patient cohort to shed further insight into the potential association between proton radiotherapy and reduced risk of liver decompensation," said Dr. Sanford as she elaborated on next steps following the completion of her group's study. "Dr. Hong is also leading a multicenter NRG randomized trial of photon versus proton radiotherapy for liver cancer with the goal of providing Level 1 evidence on the question of radiation modality for this disease."

The occurrence of RILD due to high doses of radiation has made the application of radiotherapy a topic of debate in medical circles. Because of this, radiation oncologist Dr. Cheng-En Hsieh, who works at the University of Texas MD Anderson Cancer Center in Houston and Chang Gung Memorial Hospital in Taiwan, and his colleagues sought in their own study to identify predictors of RILD in patients who underwent proton therapy.

Examining 136 HCC patients, they found that the volume of liver untouched by radiation independently predicts RILD in patients treated with proton therapy, instead of the dose of radiation delivered. If volume is sufficiently spared, ablative radiation can be safely administered with a minimal risk of RILD, regardless of dose, say the authors. They also noted that tumor size, liver volume and severity of liver disease can predict RILD prior to treatment.

"Our group (Dr. Ji-Hong Hong, Dr. Sunil Krishnan, and I) currently is performing a larger multi-institutional study to devise a new model for liver toxicity prediction in patients with hepatocellular carcinoma treated with proton radiation," said Dr. Hsieh regarding his and his colleagues' plans for studying the matter further. "We are also comparing the outcomes for patients treated with proton radiation to those treated with conventional photon radiotherapy to externally validate Dr. Sanford’s findings."

While promising, the application of proton therapy is limited by its expense and its unavailability to most patients. Further research is required for optimizing patient selection to combat these challenges, as well as for supporting protons as a better treatment option than photons for HCC, according to Dawson.

"Imbalances in factors that may alter outcomes between patients treated with photons versus protons exist. "The degree of impairment of liver function varies between patient groups and needs to be considered, as it may affect survival. Patient performance status, socioeconomic status and patient income also tend to be higher in patients treated with protons, as does ability to travel greater distances for treatment, compared with patients treated with more widely accessible photon therapy," said Dr. Dawson. "These factors are not well accounted for in retrospective studies, and randomized trials are needed to address these potential biases."

The findings for both were published in the International Journal of Radiation Oncology • Biology • Physics.

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