Abstract
Abstract
Background
We aim to quantify the dosimetric benefits of daily online adaptive (DOA) carbon ion stereotactic radiotherapy (CISR) in hepatocellular carcinoma (HCC).
Patients and methods
13 patients received 4 × 10.5 Gy (RBE-weighted dose) CISR to 14 HCC lesions in challenging locations (
N
= 10: liver dome,
N
= 3:
Results
Baseline planning target volume (PTV) and internal target volume (ITV) coverage by the prescribed dose (median coverage: PTV: 97%, ITV: 100%) significantly decreased for no adaptation (PTV: 87.6%,
p
= 0.0001; ITV: 97.7%,
p
= 0.007) and OOA (PTV: 87.8%,
p
= 0.0001; ITV: 97.7%,
p
= 0.007), while DOA maintained high PTV coverage (PTV: 95.7%,
p
= 0.17; ITV: 100%,
p
= 0.53). Frequent violations of organs-at-risk (OAR) dose constraints occurred for no adaptation and OOA (both 20/52 fractions, 38.5%). They affected the bowel, heart and esophagus up to 6 cm from the PTV. DOA led to considerably fewer (6/52 fractions, 11.5%) and less intense violations of OAR dose constraints.
Conclusions
Daily CT- and MR-guided CISR is feasible in the liver, and demonstrates frequent violations of initial treatment planning objectives when non-adaptive or offline adaptive approaches are followed. DOA could improve target coverage and OAR protection, while particularities of carbon ions such as overdoses far from the target should be considered.