influence of deformable image registration uncertainties on propagated structures for online daily adaptive proton therapy of lung cancer patients, Radiotherapy and Oncology (2021), doi:

might help us understand the biology of radiation induced liver changes and prevent toxicity. Materials/Methods: We identified 122 patients who received RT to the liver. The 1-6 month and 6-12 month post-RT MRI scans (hepatobiliary phase with gadoxetic acid) were fused to treatment planning CT scans in areas of prior RT. FLR were delineated by two independent raters. A dosevolume-histogram was used to identify the threshold isodose line (IDL) for each FLR. IDL were converted to a bioequivalent dose (BED) using a/b = 9 for liver parenchyma. MRI scans with no FLR were evaluated by a radiologist to assess for adequate contrast excretion. Results: 146 MRI scans for 100 patients were available for analysis. The median age was 65 years. Hepatocellular carcinoma accounted for 79% of cases. Baseline ALBI scores of 1,2 and 3 were observed in 26%, 57% and 17% of patients, respectively. 66% of patients had cirrhosis, with hepatitis C being most common cause (37%). The median dose delivered was 45 gray in 5 fractions. FLR were identified for 73% and 67% of patients at 1-6 months and 6-12 months. Of 26 patients with no FLR at 1-6 months, 54% exhibited poor contrast excretion. The median volume of FLR was 99 cc at 1-6 months, contracting to 43 cc at 6-12 months (P < 0.001). The median (IDL) for FLR was 3541 cGy at 1-6 months, increasing to 4519 cGy (P < 0.001). The median BED was 6355 cGy at 1-6 months, increasing to 8871 cGy (P < 0.001). There was excellent agreement between raters for the presence of FLR at 1-6 (k = 0.82) and 6-12 months (k = 0.83) and for FLR volumes (ICC of 0.94 at 1-6 and 0.88 at 6-12-months). 45 patients were evaluated at both time points. Of the 33 patients with an FLR at 1-6 months, 15% experienced resolution at 6-12 months. None of the 12 patients without an FLR on 1-6 months MRI demonstrated one at 6-12 months. On multivariate analysis, cirrhosis (PR: 1.35; P = 0.05) was associated with a higher likelihood of FLR. ALBI score 2 (PR: 0.77; P = 0.04), ALBI score 3 (PR 0.61; P = 0.01), and receipt of systemic therapy within 1 month of RT (PR: 0.74; P = 0.03) were associated a lower likelihood. Prior RT or treatment with Y-90 did not predict for FLR. Conclusion:We report the median volume, IDL and BED associated with FLR at two time points and demonstrate resolution or improvement in a significant proportion of patients over time. Absence of FLR was associated with poor liver function and contrast excretion. Excellent inter-rater agreement indicates that our results are reproducible. Additional analysis is needed to determine the clinical significance of these findings.

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