Hepatocellular carcinoma (HCC), the sixth most common
cancer in the world, is a global health concern.
Radiotherapy for HCC is uncommon, largely because of the likelihood of radiation-induced
liver disease, an acute side effect that is often fatal.
Proton beam therapy (PBT) and intensity-modulated
radiation therapy (IMRT) may offer HCC patients a better option for treating the diseased liver tissue while largely sparing the surrounding tissues, especially the non-
tumor liver. However, even advanced
radiotherapies carry a risk of late effects, including second
malignant neoplasms (SMNs). It is unclear whether PBT or IMRT confers less risk of an SMN than the other. The purpose of this study was to compare the predicted risk of developing an SMN for a patient with HCC between PBT and IMRT. For both treatments, radiation doses in organs and tissues from primary radiation were determined using a treatment planning system; doses in organs and tissues from stray radiation from PBT were determined using Monte Carlo simulations and from IMRT using thermo-luminescent
dosimeter measurements. Risk models of SMN incidence were taken from the literature. The predicted absolute lifetime attributable risks of SMN incidence were 11.4% after PBT and 19.2% after IMRT. The results of this study suggest that using
proton beams instead of photon beams for
radiotherapy may reduce the risk of SMN incidence for some HCC patients.