Dosimetric superiority of proton radiosurgery in liver cancer: an in silico comparative dosimetric study

This in silico dosimetric study aimed to evaluate a potentially more efficient approach by assessing the dosimetric advantages of single-fraction 35 Gy proton radiosurgery relative to photon therapy.

This retrospective study included 98 patients with liver cancer who had undergone radiotherapy. Simulated treatment plans were generated for each patient to deliver a single fraction of 35 Gy using both photon and proton techniques. Patients were defined as eligible if all organs at risk (OARs) met the preset dose constraints. The Wilcoxon signed-rank test was applied to compare dosimetric parameters. The Youden index was used to identify the optimal cutoff for the safety margin between the OARs and the gross tumor volume.

Proton therapy demonstrated a higher overall compliance rate with dose constraints compared to photon therapy, with notable improvements for key OARs, including the liver (96.9% vs. 88.8%), duodenum (93.9% vs. 91.8%), and heart (91.8% vs. 89.8%). Proton therapy plans provided superior sparing of OARs by significantly reducing the maximum dose to all organs (p < 0.0001) and the optimal cutoff for satisfying dose constraints was generally < 1 cm. Furthermore, proton therapy significantly reduced the irradiated liver volume (V5Gy and V11.6 Gy, both p < 0.05), and this benefit was consistent across tumor sizes (≤ 3 cm or > 3 cm) and locations (dome, caudal, left medial, or central).

Single-fraction 35 Gy proton radiosurgery offers enhanced sparing of OARs and a broader therapeutic window for patients with liver cancer compared with photon therapy from a dosimetric perspective. Whether these dosimetric benefits can translate into actual clinical efficacy requires prospective validation.