Do hepatocellular carcinomas located in subcapsular space or in proximity to vessels increase the rate of local tumor progression? A meta-analysis

To determine if tumors located in the subcapsular space or in proximity to vessels would be a risk factor of local tumor progression (LTP2) in hepatocellular carcinomas (HCC) after radiofrequency ablation.A search of the MEDLINE, EMBASE and Cochrane Library databases from 1998 to 2017 was performed to identify studies examining the risk factors of LTP after radiofrequency ablation (RFA3) in HCC. No language or other restrictions were imposed. Summary estimates of risk factors of LTP were obtained by using a random-effects model with further exploration with meta-regression and sub-group analyses.There were 16 studies included, of which 7 were focused on the association of LTP with tumors abutting vessels, and 15 focused on tumors of subcapsular location. In total, 2870 patients were included. Tumors that were located in the subcapsular area had a higher occurrence of LTP (P = 0.04) with a high heterogeneity (I2 = 65%), which could not be explained by the results of the meta-regression. However, tumor that were in close to vessels had contrary results (P = 0.54) with a high heterogeneity (I2 = 77%).The findings of the present meta-analysis indicate that the subscapsular location is a possible risk factor of LTP. Nevertheless, a clear definition or classification of the subcapsular location should be highlighted in future studies. Whether tumor location adjacent to a vessel has an influence on the incidence of LTP remains controversial, and more relevant research should be performed.