A multi-center retrospective study evaluated hepatocellular carcinoma (HCC) patients treated with radioembolization across four distinct clinical sites. The investigation included 75 patients treated between January 2007 and April 2015 at the University Hospital Essen in Germany, serving as the training cohort. Validation cohorts comprised 49 patients treated between November 2009 and March 2016 at University Hospital Rennes in France, 17 patients treated between August 2012 and December 2017 at University Hospital Münster in Germany, and 5 patients treated between June 2010 and December 2014 at University Hospital Würzburg in Germany. Treatment indications across these groups included unresectability, size alternatives to transarterial chemoembolization, and bridge to liver transplantation in 10% of cases.
Multi-Center Cohort Design and Microsphere Selection in Radioembolization
Intervention parameters varied by facility regarding the radioactive source material deployed. Patients in the training cohort from Essen and the validation cohort from Rennes received glass 90Y microspheres. Conversely, the cohorts treated at Münster and Würzburg received resin 90Y microspheres. Across all groups, approximately half of the patients underwent liver biopsy for diagnosis, while the remaining individuals were diagnosed exclusively through imaging.
Volumetric Analysis and Imaging Protocols
Volumetric assessments relied on baseline computed tomography or magnetic resonance imaging scans performed within a maximum of 6 weeks prior to radioembolization, alongside follow-up imaging at least 1 month later. Hepatic segment classification followed Couinaud segmentation, adjusted when necessary with single-photon emission computed tomography information gathered during the planning phase. Volumetry utilized site-specific techniques on modern CT scanners with 3 to 5 mm thick reconstructed slices, employing manual summation or automatic calculation on data-processing consoles.
Measurements captured left lobe, right lobe, and total liver volumes in milliliters, from which the future liver remnant was computed as the ratio of left lobe volume to total volume. Baseline total splenic volume was also recorded. In the Essen training cohort, follow-up imaging occurred at 3, 6, and 9 months, though 14 patients missed 9-month scans; for those instances, liver volume at 9 months was estimated by calculating the mean difference between 6-month and 9-month follow-up values across the remaining cohort. Validation cohorts utilized varying follow-up time points, such as 4 or 7 months, with up to three follow-up measurements available per patient.
Clinical Features and Baseline Characteristics
Chart reviews supplied comprehensive baseline characteristics and laboratory results for all cohorts. Evaluated laboratory features included prothrombin time via international normalized ratio, albumin, thrombocyte count, and total bilirubin. Clinical features documented during initial evaluations included sex, cirrhosis etiology, Child-Pugh score, ascites, portocaval shunting on initial cross-sectional imaging, and portal vein thrombosis. Cases lacking evidence of cirrhosis had their Child-Pugh score set to zero. All clinical and laboratory features, excluding baseline volumes, were scaled to achieve a mean of zero and a variance of 1.
Biophysical Properties and Historical Context of 90Y Radiation
Intraarterial injection of the radioactive isotope 90Y has a lengthy history in clinical literature dating back to initial trials in 1965 targeting primary liver and pancreatic malignancies. The isotope functions as a beta-radiation emitter with a mean decay energy of 0.94 MeV, generating cellular breakdown and tumor necrosis upon delivery to target sites. With a half-life of approximately 64 hours and tissue penetration restricted to roughly 1 cm, exposure to surrounding healthy parenchyma remains limited. This intraarterial delivery method places the highest possible radiation dose adjacent to the tumor while minimizing systemic exposure and reducing radiation risks for medical personnel and patient families.
Historical challenges in managing hepatocellular carcinoma involved poor response rates to systemic chemotherapy and radiosensitive parenchyma damage from external-beam radiation. Initial studies established that intraarterial 90Y microspheres induced significant tumor necrosis in radiosensitive tumors, enhancing vascularity and extending lifespan in unresectable disease. Subsequent clinical evaluations demonstrated that 90Y radioembolization yielded outcomes comparable to or exceeding other locoregional treatments like transarterial chemoembolization or thermal ablation in localized disease.
Malignancy Classifications and Metastatic Considerations
Beyond hepatocellular carcinoma, intrahepatic cholangiocarcinoma represents the second most common primary liver malignancy. Unresectable cases carry a poor prognosis, though combination chemotherapy regimens involving gemcitabine and cisplatin improve overall survival despite systemic toxicity. Palliative treatment utilizing 90Y radioembolization offers improved median survival with limited side effects for this radiosensitive malignancy.
Colorectal cancer frequently metastasizes to the liver due to portal venous drainage from the intestines. Standard metastatic therapy relies on fluorouracil, leucovorin, and oxaliplatin chemotherapy, though combination with 90Y radioembolization provides therapeutic utility for chemotherapy-refractory patients.
