Abstract
IntroductionStrong correlation has been demonstrated between tumor dose and response and between healthy liver dose and side effects. Individualized dosimetry is increasingly recommended in the current clinical routine. However, hepatic and tumor segmentations could be complex in some cases. The aim of this study is to assess the reproducibility of the tumoral and non-tumoral liver dosimetry in selective internal radiation therapy (SIRT).Material and methodsTwenty-three patients with hepatocellular carcinoma (HCC) who underwent SIRT with glass microspheres were retrospectively included in the study. Tumor (TV) and total liver volumes (TLV), and mean absorbed doses in tumoral liver (TD) and non-tumoral liver (THLD) were determined on the 90Y PET/CT studies using Simplicit90YTM software, by three independent observers. Dosimetry datasets were obtained by a medical physicist helped by a nuclear medicine (NM) physician with 10 years of experience (A), by a NM physician with 4-year experience (B), and by a resident who first performed 10 dosimetry assessments as a training (C). Inter-observer agreement was evaluated using intra-class correlation coefficients (ICC), coefficients of variation (CV), Bland-Altman plots, and reproducibility coefficient (RDC).ResultsA strong agreement was observed between all three readers for estimating TLV (ICC 0.98) and THLD (ICC 0.97). Agreement was lower for TV delineation (ICC 0.94) and particularly for TD (ICC 0.73), especially for the highest values. Regarding TD, the CV (%) was 26.5, 26.9, and 20.2 between observers A and B, A and C, and B and C, respectively, and the RDC was 1.5. Regarding THLD, it was 8.5, 12.7, and 9.4, and the RDC was 1.3.ConclusionUsing a standardized methodology, and regardless of the different experiences of the observers, the estimation of THLD is highly reproducible. Although the reproducibility of the assessment of tumor irradiation is overall quite high, large variations may be observed in a limited number of patients.
Highlights
Strong correlation has been demonstrated between tumor dose and response and between healthy liver dose and side effects
A strong agreement was observed between all three readers for estimating total liver volumes (TLV) (ICC 0.98) and Total healthy liver dose (THLD) (ICC 0.97)
Agreement was lower for Tumoral volume (TV) delineation (ICC 0.94) and for Tumoral dose (TD) (ICC 0.73), especially for the highest values
Summary
Strong correlation has been demonstrated between tumor dose and response and between healthy liver dose and side effects. The aim of this study is to assess the reproducibility of the tumoral and non-tumoral liver dosimetry in selective internal radiation therapy (SIRT). Correlations have been established between tumor dose and response, on the one hand, and between healthy liver dose and side effects, on the other hand [11, 12]. A key step in the dosimetry process is the identification and the segmentation of the target volumes This may prove highly complex, especially in case of multifocal HCC or diffuse metastatic disease, and may generate an inter-observer variability of volumes measurements and of estimated doses. The only research investigating dose measurements reported a clinically acceptable inter-observer variability for healthy liver but larger fluctuations for assessing the dose to neoplastic lesions [14]
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