Evaluation of factors affecting tumor response and survival in patients with primary and metastatic liver cancer treated with microspheres

Radioembolization with Y-90 microsphere is becoming an increasingly used modality in the treatment of patients with primary or metastatic liver cancer. Although Tc-99m MAA scintigraphy performed following diagnostic angiography has an important role in predicting effectiveness of treatment and dose estimation, number of studies using quantitative assessment of Tc-99m MAA scintigraphy is limited in this field. In the present study, the aim was to assess whether a tumor dose is required to obtain objective tumor response and to check whether this threshold value is predictive in terms of tumor response, survival and liver toxicity by using Tc-99m MAA SPECT images. Methods: Overall, 54 patients (20 women, 34 men; median age: 60 years) who underwent Y-90 Resin (SIR-Spheres®) and Glass (TheraSphere®) microsphere treatment with a diagnosis of unresectable liver cancer between August, 2010 and April, 2013 were included to the study. Mean doses to normal liver and tumor were estimated for each patient by using Tc-99m MAA SPECT images and MIRD (The Medical Internal Radiation Dosimetry) method. The responses were assessed according to RECIST and EORTC criteria. Kaplan-Meier survival curves and univariate cox regression analysis were used in survival analysis. The relationship between treatment response and other parameters included were assessed by using logistic regression analysis. The variables with a p value<0.01 in univariate analysis were assessed by multivariate analysis. Results: Fifty-four Y-90 microsphere treatments (8 by using Y-90 glass microsphere and 46 by using Y-90 resin microsphere) were performed. In the multivariate analysis, the only parameter related to response was tumor dose (p<0.01). By a tumor dose of ?250 Gy, objective tumor response was observed in 59% and 77% of the patients according to RECIST and EORTC criteria, respectively and tumor control rate was found as 95% according to both criteria. In addition, it was found that only tumor absorbed dose was correlated with progression-free survival (p<0.001) and overall survival (p=0.018). When tumor dose was 250 Gy or higher, median PFS increased from 2 to 10.7 months (p<0.001), while median OS from 9 to 17.6 months (p=0.018). However, reversible ?G2 liver toxicity was observed in 3.7% (2/54) of the patients within 3 months after radioembolization by a median liver dose of 40 Gy (10-102 Gy). There was reversible ?G3 liver toxicity in 3.7% (2/54) of the patients while no G4 liver toxicity was observed. Clinical radiation hepatitis and treatment-induced liver failure wasn?t observed in any of these patients. Conclusion: The Tc-99m MAA SPECT has a predictive value in terms response to radioembolization, progression-free and overall survival. Dosimetry based on Tc-99m MAA SPECT images can be used in the selection of the patients and, in particular, to adaptation of treatment plan in selected patients