Functional Liver Imaging and Dosimetry to Predict Hepatotoxicity Risk in Cirrhotic Patients With Primary Liver Cancer.

PURPOSE: Mitigating radiation-induced liver disease (RILD) is an ongoing need in patients with hepatocellular carcinoma. We hypothesize that [99mTc]-sulfur colloid (SC) single photon emission computed tomography (SPECT)/computed tomography (CT) scans can provide global functional liver metrics and functional liver dosimetric parameters that are predictive of hepatotoxicity risk in patients with primary liver cancer with cirrhosis. MATERIALS AND METHODS: We retrospectively reviewed 47 patients (n = 26 proton, n = 21 stereotactic body radiation therapy) with Child-Pugh (CP)-A (62%) or CP-B (38%) cirrhosis who underwent SC SPECT/CT scans for radiation therapy planning. SC SPECT scans were mined for image intensity threshold-based functional liver volumes (FLV), mean liver-spleen uptake ratio (L/Smean), and total liver function (TLF = FLV*L/Smean). Radiation therapy doses were voxel-wise converted to the biologically equivalent dose (EQD2a/b=3) and relative biological effectiveness (GyRBE). Normal liver (liver minus gross tumor volume [GTV]) and FLV mean doses, absolute and relative dose-volumes (VGy[cc], VGy[%]), and relative dose-function histogram quantiles in 10 GyEQD2 increments were calculated. Logistic regression was performed for correlation to CP score increase of 2 or higher (CP+2). Cox regression was performed for correlation to RILD-specific survival (RILD-SS) and overall survival. RESULTS: The strongest predictors of RILD-SS were FLV V20 and liver-GTV F20. FLV mean dose, but not CT-derived anatomic mean dose, was predictive of RILD-SS. TLF and L/Smean were the only parameters that were associated with CP+2 after adjusting for baseline CP score. Optimal cutoffs to mitigate risk RILD-SS were identified: FLV mean dose <23 GyEQD2, liver-GTV V20 <36%, FLV V20 <36%, liver-GTV F20 <36%, FLV <32% (350 cc), L/Smean >0.75, TLF >0.60, tumor volume <40 cm3, and CP score A5-6 versus B7-C10. A narrower therapeutic window was observed in CP-B/C patients. The discriminatory power for RILD-SS within CP-B/C classes was improved with the addition of a functional dosimetric constraint, resulting in low- and high-risk subgroups (P = 3 × 10-6). CONCLUSIONS: Functional liver metrics and dosimetric parameters derived from pretreatment SC SPECT/CT scans were complementary predictors of hepatotoxicity and may provide useful clinical decision support in the management of cirrhotic patients with primary liver cancer.