Low-dose CT angiography: which contrast medium? Reply.

Aims: This prospective pilot study investigated the feasibility of perfusion computed tomography parameters as surrogate markers of angiogenesis and early response following sorafenib administration in patients with advanced hepatocellular carcinoma. Methods: Ten patients were evaluated with perfusion computed tomography before starting sorafenib and after 3 months. Blood flow, blood volume, mean transit time, hepatic arterial fraction, and permeability surface-product were compared in tumour lesions and in hepatic parenchyma at baseline and at follow-up. Correlation between these parameters and changes in alpha-fetoprotein levels was calculated. Results: At baseline, blood volume, blood flow, hepatic arterial fraction and permeability surface values were higher in lesions compared to those in hepatic parenchyma, while mean transit time was lower (p < 0.05). After sorafenib treatment, only mean transit time was significantly increased versus baseline (p < 0.05). At follow-up, plasma alpha-fetoprotein levels decreased in all patients. At follow-up, an inverse correlation was observed between baseline mean transit time and changes in alpha-fetoprotein (r = -0.6685, p = 0.0125), as well as a correlation between baseline blood flow and alpha-fetoprotein (r = 0.6476, p = 0.0167). Conclusion: This pilot study suggests that after sorafenib treatment an increase in mean transit time observed in tumour lesions is inversely correlated with alpha-fetoprotein reductions after therapy. Mean transit time may represent a possible marker of response irrespectively of alpha-fetoprotein values.