Comparison of PERCIST and RECIST criteria for evaluation of therapy response after yttrium-90 microsphere therapy in patients with hepatocellular carcinoma and those with metastatic colorectal carcinoma.

Objective: Yttrium-90 (Y) microsphere therapy has been increasingly used to treat hepatocellular carcinoma (HCC) and liver metastasis of colorectal cancer (mCRC). This study aims to compare two different criterias used for therapy response evaluation following Y therapy within the same group of patients.

Patients And Methods: A total of 21 patients with HCC and 19 patients with mCRC were included in this study, with 36 and 42 liver lesions, respectively. The lesions were evaluated before and after therapy by CT or MRI and fluorine-18 fluorodeoxyglucose (F-FDG) PET/CT. Several metabolic parameters were analyzed including maximum and mean standardized uptake values, peak standardized uptake value, metabolic tumor volume (MTV), and total lesion glycolysis. Tumor volume was determined using CT or MRI images for all lesions, and the applied activity was estimated to deliver 120±20 Gy for the treated lobe. Six weeks after Y microsphere therapy, F-FDG PET/CT scan was performed to evaluate tumor response using PERCIST and RECIST criteria. Overall survival was calculated using Kaplan-Meier method.

Results: A total of 78 liver lesions were treated without any major complication. The mean tumor volumes of HCC lesions calculated by CT or MRI before and after therapy were 84.38 and 86.62 cm, respectively. The average MTV of these lesions on PET images was calculated as 68.142 mm before therapy and 56.945 mm after treatment. In patients with mCRC, the mean tumor volume was 52.32 cm before therapy and 54.52 cm after therapy. The average MTV was calculated as 41.720 mm before and 44.967 mm after therapy for the same patient group. Response Evaluation Criteria In Solid Tumors (RECIST) and PET Response Criteria In Solid Tumors incompatibility was seen in seven of 36 lesions in HCC-diagnosed patients and seven of 42 lesions in patients with mCRC. The mean overall survival was calculated as 13.09 months in patients with HCC and 10.6 months in patients with mCRC.

Conclusion: Y therapy response can be evaluated by both RECIST and European Organization for Research and Treatment of Cancer criteria. However, RECIST and European Organization for Research and Treatment of Cancer incompatibility can be seen. The anatomic methods for evaluating HCC response is relatively more accurate, whereas the metabolic parameters guided by PET/CT scan showed greater importance in response to evaluation of liver mCRC.