Response requisites.

Treating hepatocellular carcinoma (HCC) with stereotactic body radiation (SBRT) usually happens only after surgeons and/or interventional radiologists have taken their shots. So do the same imaging response criteria still apply? Per the European Association for the Study of the Liver (EASL) and the modified Response Evaluation Criteria in Solid Tumors (mRECIST), enhancement is “the” distinguishing feature of viable versus necrotic residual HCC. A small but provocative case series out of the University of Michigan questions this universal tenet in the post-SBRT setting. Of 146 patients with HCC treated at their institution, there were 10 clinical complete responses confirmed by pathologic examination or normalization of alpha-fetoprotein levels. Four of these 10 showed persistent arterial enhancement (“stable” disease per mRECIST) and 9 of 10 showed persistent wash-out--both occuring up to 12 months post-SBRT. This could be related to radiation-induced peritumoral hypervascularity, though no one really knows. In any case, the numbers are small but the message is big: a treatment with unique biological sequelae calls for unique response criteria...or risk hella over treating HCC.