Speaker
Description
Introduction
Radiotherapy is an effective local treatment option in patients with hepatocellular carcinoma (HCC). However, photon radiotherapy is not a widely used modality in HCC as most patients have underlying cirrhosis making the liver more sensitive to radiation induced liver disease (RILD).
The aim of this national phase II study (NCT05203120) is to investigate feasibility and safety of exhale gated proton therapy in HCC patients with large tumors up to 12 cm and impaired liver function.
Methods
50 patients will be included over 3 years starting from April 2022. Patients must not be candidate for any other curative treatment strategies as resection or radiofrequency ablation (RFA). Maximum 3 tumors in the liver are allowed with a maximum tumor size of 12 cm in total. The maximum Child-Pugh score allowed is B8. Patients are followed closely during and after treatment in order to capture toxicity.
Before treatment planning, 2-4 fiducials markers are implanted around the tumor(s). The patients are positioned in supine position with arms up with an external marker box for gating. A 4DCT scan without contrast, a triple phase 3DCT with contrast and an MRI with contrast are obtained for delineations and treatment planning. A GTV is defined using the triple phase 3DCT and a 5 mm isotropic margin is added to create the CTV. A target iCTV is defined on the exhale phase of the 10-phase p4DCT as the union of the CTVs in the 5 phases closest to exhale.
Treatment plans are created on the exhale phase using 3 fields and robust single field optimization
Patients are treated with either 58 GyRBE (if CTV < 1.5 cm to porta hepatis) or 67 GyRBE in 15 fractions.
Daily setup is based on free-breathing CBCT with manual match to the motion-blurred exhale position of the implanted markers. Weekly control CT scans are acquired.
Investigations within the study includes comparative photon VMAT plans, target motion variability between planning 4DCT and respiratory gated treatment fractions and motion-including tumor dose reconstruction for individual treatment fractions.
Results
So far, 18 patients have been treated successfully using gated proton therapy treatment in the study. No replans have been performed based on weekly control CT scans. The mean dose to the healthy liver has been reduced with 39% in average (range, 23% to 60%) compared to comparative photon VMAT plans. Toxicity data have not been analyzed yet.
For the first 6 patients, the full motion of the markers in CC direction was 11.5±3.2mm (mean±SD) during 4DCT and 20.2±4.1mm during CBCT. The 50th percentile motion in CC direction was 3.7±1.4mm (mean±SD) during 4DCT and 4.8±1.7mm during CBCT. Respiratory exhale gating effectively limited both motion and motion variability.
