Letter to the editor regarding quantitative dynamic contrast-enhanced ultrasound may help predict the outcome of hepatocellular carcinoma after microwave ablation

Sir,

With interest, we read the article by Zhan et al. published in the International Journal of Hyperthermia in October 2018 [1]. Liver cancer is one of the major causes of cancer-related deaths. Curative-intended resection or ablation is associated with a high recurrence rate. The purpose of this prospective study [1] was to illuminate the correlation of dynamic contrast-enhanced ultrasound (DCE-US) parameters and prognosis of hepatocellular carcinoma (HCC) patients after microwave ablation (MWA). A total of 35 patients were enrolled. And correlation analysis between parameters of DCE-US and the histopathology results was performed. Microvessel density was found positively correlated with IMAX (a DCE-US parameter) and negatively correlated with time to peak (TTP) (both p < .01). And positive correlations were shown between IMAX and vascular endothelial growth factor (VEGF) expression (p < .01). The authors concluded DCE-US parameter may predict the prognosis of HCC patients after MWA.

However, certain issues must be addressed, regarding the methodology. These estimates, are not the most suitable for prediction studies. Firstly, correlation, even with statistical significance (p < .01), could not guarantee prediction of a certain outcome. Furthermore, for prediction study, we need data from two distinct cohorts, or at least from one single cohort but divided into two, first to build a prediction model and then to validate it. Misleading results are generally the major outcome of research without validation of prediction models [2,3]. Finally, in prediction study, we should evaluate the interactions between important variables [2]. Final results could be affected dramatically if qualitative interactions are present, which means without evaluating interaction terms, prediction studies will mainly convey misleading messages.

Disclosure statement

No potential conflict of interest was reported by the authors.