Radioembolization of hepatocarcinoma with 90Y glass microspheres: treatment optimization using the dose-toxicity relationship.

AIM: Transarterial radioembolization (TARE) is, by all standards, a radiation therapy. As such, according to Euratom Directive 2013/59, it should be optimized by a thorough treatment plan based on the distinct evaluation of absorbed dose to the lesions and to the non-tumoural liver (two-compartment dosimetry). Since the dosimetric prediction with 99mTc albumin macro-aggregates (MAA) of non-tumoural liver is much more accurate than the same prediction on lesions, treatment planning should focus on non-tumoural liver rather than on lesion dosimetry. The aim of this study was to determine a safety limit through the analysis of pre-treatment dosimetry with 99mTc-MAA single photon emission computed tomography (SPECT/CT), in order to deliver the maximum tolerable absorbed dose to non-tumoural liver. METHODS: Data from intermediate/advanced hepato-cellular carcinoma (HCC) patients treated with 90Y glass microspheres were collected in this single-arm retrospective study. Injection was always lobar, even in case of bilobar disease, to avoid treating the whole liver in a single session. A three-level definition of liver decompensation (LD) was introduced, considering toxicity only in cases of liver decompensation requiring medical action (LD type C, LDC). We report LDC rates, receiver operating characteristic (ROC) analysis between LDC and NO LDC absorbed dose distributions, normal tissue complication probability (NTCP) curves and uni- and multivariate analysis of risk factors associated with toxicity. RESULTS: A 6-month timeline was defined as necessary to capture all treatment-related toxicity events. Previous transarterial chemoembolization (TACE), presence or extension of portal vein tumoural thrombosis (PVTT) and tumour pattern (nodular versus infiltrative) were not associated with tolerance to TARE. On the contrary, at the multivariate analysis, the absorbed dose averaged over the whole non-tumoural liver (including the non-injected lobe) was a prognostic indicator correlated with liver decompensation (odds ratio = 4.24). Basal bilirubin > 1.1 mg/dL was a second even more significant risk factor (odds ratio = 6.35). NTCP analysis stratified with this bilirubin cut-off determined a 15% liver decompensation risk at 50 Gy/90 Gy for bilirubin >/< 1.1 mg/dL. These results are valid for a 90Y glass microsphere administration 4 days after the reference time. CONCLUSION: Given the low predictive accuracy of 99mTc-MAA on lesion absorbed dose reported by several authors, an optimized TARE with 90Y glass microspheres with lobar injection 4 days after reference time should aim at an absorbed dose averaged over the whole non-tumoural liver of 50 Gy/90 Gy for basal bilirubin higher/lower than 1.1 mg/dL, respectively.

Post-liver transplant intrahepatic cholestasis: etiology, clinical presentation, therapy.

Post-liver transplant intrahepatic cholestasis is consequent to the impairment of bile flow or formation. It may develop in the early (within 6 months) or in the late (more than 6 months) post-liver transplant period and different causes may be recognized according to the time elapsed from a liver transplant. The raise at various degrees of serum bilirubin, alkaline phosphatase, and gamma-glutamyl transpeptidase, with or without increased transaminases levels, are common hematochemical findings. Liver histology is helpful for diagnostic assessment, and sometimes crucial to differentiate among possible causes of cholestasis. Although timely treatment of underling conditions as well as supportive care may resolve post-liver transplant intrahepatic cholestasis, the risk of graft loss and retransplantation are remarkable. For this reason, post-liver transplant intrahepatic cholestasis should be managed in collaboration with the LT center, and treatment should be devolved to expert hepatologists.

The Long-Term Benefit of Liver Transplantation for Hepatic Metastases From Neuroendocrine Tumors.

Selection criteria and benefit of liver transplantation for hepatic metastases from neuroendocrine tumors (NETs) remain uncertain. Eighty-eight consecutive patients with metastatic NETs eligible for liver transplantation according to Milan-NET criteria were offered transplant (n = 42) versus nontransplant options (n = 46) depending on list dynamics, patient disposition, and age. Tumor burden between groups did not differ. Transplant patients were younger (40.5 vs. 55.5 years; p < 0.001). Long-term outcomes were compared after matching between groups made on multiple Cox models adjusted for propensity score built on logistic models. Survival benefit was the difference in mean survival between transplant versus nontransplant options. No patients were lost or died without recurrence. Median follow-up was 122 months. The transplant group showed a significant advantage over nontransplant strategies at 5 and 10 years in survival (97.2% and 88.8% vs. 50.9% and 22.4%, respectively; p < 0.001) and time-to-progression (13.1% and 13.1% vs. 83.5% and 89%; p < 0.001). After adjustment for propensity score, survival advantage of the transplant group was significant (hazard ratio = 7.4; 95% confidence interval (CI): 2.4-23.0; p = 0.001). Adjusted transplant-related survival benefit was 6.82 months (95% CI: 1.10-12.54; p = 0.019) and 38.43 months (95% CI: 21.41-55.45; p < 0.001) at 5 and 10 years, respectively. Liver transplantation for metastatic NETs under restrictive criteria provides excellent long-term outcome. Transplant-related survival benefit increases over time and maximizes after 10 years.

Radioembolization of hepatocarcinoma with (90)Y glass microspheres: development of an individualized treatment planning strategy based on dosimetry and radiobiology.

PURPOSE: The aim of this study was to optimize the dosimetric approach and to review the absorbed doses delivered, taking into account radiobiology, in order to identify the optimal methodology for an individualized treatment planning strategy based on (99m)Tc-macroaggregated albumin (MAA) single photon emission computed tomography (SPECT) images. METHODS: We performed retrospective dosimetry of the standard TheraSphere® treatment on 52 intermediate (n = 17) and advanced (i.e. portal vein thrombosis, n = 35) hepatocarcinoma patients with tumour burden < 50% and without obstruction of the main portal vein trunk. Response was monitored with the densitometric radiological criterion (European Association for the Study of the Liver) and treatment-related liver decompensation was defined ad hoc with a time cut-off of 6 months. Adverse events clearly attributable to disease progression or other causes were not attributed to treatment. Voxel dosimetry was performed with the local deposition method on (99m)Tc-MAA SPECT images. The reconstruction protocol was optimized. Concordance of (99m)Tc-MAA and (90)Y bremsstrahlung microsphere biodistributions was studied in 35 sequential patients. Two segmentation methods were used, based on SPECT alone (home-made code) or on coregistered SPECT/CT images (IMALYTICS™ by Philips). STRATOS™ absorbed dose calculation was validated for (90)Y with a single time point. Radiobiology was used introducing other dosimetric variables besides the mean absorbed dose D: equivalent uniform dose (EUD), biologically effective dose averaged over voxel values (BEDave) and equivalent uniform biologically effective dose (EUBED). Two sets of radiobiological parameters, the first derived from microsphere irradiation and the second from external beam radiotherapy (EBRT), were used. A total of 16 possible methodologies were compared. Tumour control probability (TCP) and normal tissue complication probability (NTCP) were derived. The area under the curve (AUC) of the receiver-operating characteristic (ROC) curve was used as a figure of merit to identify the methodology which gave the best separation in terms of dosimetry between responding and non-responding lesions and liver decompensated vs non-decompensated liver treatment. RESULTS: MAA and (90)Y biodistributions were not different (71% of cases), different in 23% and uncertain in 6%. Response correlated with absorbed dose (Spearman's r from 0.48 to 0.69). Responding vs non-responding lesion absorbed doses were well separated, regardless of the methodology adopted (p = 0.0001, AUC from 0.75 to 0.87). EUBED gave significantly better separation with respect to mean dose (AUC = 0.87 vs 0.80, z = 2.07). Segmentation on SPECT gave better separation than on SPECT/CT. TCP(50%) was at 250 Gy for small lesion volumes (<10 cc) and higher than 1,000 Gy for large lesions (>10 cc). Apparent radiosensitivity values from TCP were around 0.003/Gy, a factor of 3-5 lower than in EBRT, as found by other authors. The dose-rate effect was negligible: a purely linear model can be applied. Toxicity incidence was significantly larger for Child B7 patients (89 vs 14%, p < 0.0001), who were therefore excluded from dose-toxicity analysis. Child A toxic vs non-toxic treatments were significantly separated in terms of dose averaged on whole non-tumoural parenchyma (including non-irradiated regions) with AUC from 0.73 to 0.94. TD50 was ≈ 100 Gy. No methodology was superior to parenchyma mean dose, which therefore can be used for planning, with a limit of TD15 ≈ 75 Gy. CONCLUSION: A dosimetric treatment planning criterion for Child A patients without complete obstruction of the portal vein was developed.

A dosimetric treatment planning strategy in radioembolization of hepatocarcinoma with 90Y glass microspheres.

AIM: Our goal was to limit liver toxicity and to obtain good efficacy by developing a dosimetric treatment planning strategy. While several dosimetric evaluations are reported in literature, the main problem of the safety of the treatment is rarely addressed. Our work is the first proposal of a treatment planning method for glass spheres, including both liver toxicity and efficacy issues. METHODS: Fifty-two patients (series 1) had been treated for intermediated/advanced hepatocellular carcinoma (HCC) with glass spheres, according to the Therasphere® prescription of 120 Gy averaged on the injected lobe. They were retrospectively evaluated with voxel dosimetry, adopting the local deposition hypothesis. Regions of interest on tumor and non tumor parenchyma were drawn to determine the parenchyma absorbed dose, averaged also on non irradiated voxels, excluding tumor voxels. The relationship between the mean non tumoral parenchyma absorbed dose D and observed liver decompensation was analyzed. RESULTS: Basal Child-Pugh strongly affected the toxicity incidence, which was 22% for A5, 57% for A6, 89% for B7 patients. Restricting the analysis to our numerically richest class (basal Child-Pugh A5 patients), D median values were significantly different between toxic (median 90 Gy) and non toxic treatments (median 58 Gy) at a Mann-Withney test, (P=0.033). Using D as a marker for toxicity, the separation of the two populations in terms of area under ROC curve was 0.75, with 95% C.I. of [0.55-0.95]. The experimental Normal Tissue Complication Probability (NTCP) curve as a function of D resulted in the following values: 0%, 14%, 40%, 67% for D interval of [0-35] Gy, [35-70] Gy, [70-105] Gy, [105-140] Gy. DISCUSSION: A limit of about 70 Gy for the mean absorbed dose to parenchyma was assumed for A5 patients, corresponding to a 14% risk of liver decompensation. This result is applicable only to our administration conditions: glass spheres after a decay interval of 3.75 days. Different safety limit (40 Gy) are published for resin spheres, characterized by higher number of particle per GBq (more uniform irradiation, bigger biological effect for the same absorbed dose). CONCLUSION: As result of this study we suggest a constraint of about 70 Gy mean absorbed dose to liver non tumoral parenchyma, corresponding to about 15% probability of radioinduced liver decompensation while still aiming at achieving an absorbed of several hundreds of Gy to lesions.

Need, feasibility and convenience of dosimetric treatment planning in liver selective internal radiation therapy with (90)Y microspheres: the experience of the National Tumor Institute of Milan.

In most centres, the choice of the optimal activity to be administered in selective intra-arterial radioembolization with microspheres is nowadays based on empirical models which do not take into account the evaluation of tumour and non tumour individual absorbed dose, despite plenty of published data which showed that local efficacy is correlated to tumour absorbed dose, and that the mean absorbed dose is a toxicity risk factor. A pitfall of the crudest, empirical tumour involvement method are 20 deaths in a single centre which adopted it to administer the whole liver, or the need of systematic 25% subjective reduction of activity prescribed with body surface area method. In order to develop a possibly safer and more effective strategy based on real individual dosimetry, we examine first external beam liver radiation therapy results. The half century experience has something to be borrowed: the volume effect, according to which the smaller the fraction of the irradiated liver volume, the higher the tolerated dose. Different tolerance for different underlying disease or previous non radiation treatment is to be expected. Radiobiological models experience also has to be inherited, but not their dose reference values. Then we report the published dosimetric experience about (90)Y microsphere radioembolization of primary and metastatic liver tumours. In addition we also present original data from our growing preliminary experience of more refined (99m)Tc MAA SPECT based calculations in hepatocarcinoma patients. This overcame the mean dose approach in favour of the evaluation of dose distribution at voxel level. An insight into dosimetry issues at microscopic level (lobule level) is also provided, from which the different radiobiological behaviour between resin and glass spheres can be understood. For tumour treatment, an attenuation corrected (99m)Tc- SPECT based treatment planning strategy can be proposed, although quantitative efficacy thresholds should be differentiated according to the kind of pathology and previous treatment. For non tumour liver parenchyma, data in favour of a relationship between absorbed dose and dangerous effects are encouraging. Unfortunately in hepato-cellular carcinoma, some confounding factors may hamper the adequate estimation of the risk of toxicity. First there is a lack of consensus about the exact definition of toxicity after (90)Y microsphere radioembolization. Second, for HCC patients, progression of both cancer and cirrhosis can simulate a radioinduced toxicity, making the analysis more complex.