Response to intra-arterial oncolytic virotherapy with the herpes virus NV1020 evaluated by [18F]fluorodeoxyglucose positron emission tomography and computed tomography.

Oncolytic virotherapy poses unique challenges to the evaluation of tumor response. We hypothesized that the addition of [(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET) to standard computed tomography (CT) evaluation would improve diagnostic and prognostic power of the measurement of tumor response to oncolytic virotherapy. A phase I/II trial was conducted to investigate treatment of hepatic metastases from colorectal carcinoma using intra-arterial administration of the oncolytic herpes virus NV1020. Both contrast-enhanced CT and FDG PET were obtained on each patient at each time point. Quantitative FDG PET and CT responses were correlated with each other and with clinical outcome metrics. A majority of patients showed initial post-viral infusion increases in tumor size (69%) or in standardized uptake value (SUV) (80%) large enough to qualify as progressive disease. Most showed subsequent decreases in tumor size (64%) or SUV (83%) enough to be reclassified as partial response or stable disease. Late PET and CT imaging results correlated well with each other and with clinical outcomes, but results from early in the treatment scheme did not correlate with each other, with later results, or with clinical outcomes. The addition of FDG PET to the evaluation of tumor response to the oncolytic virus NV1020 did not provide useful diagnostic or prognostic data. More sophisticated molecular imaging will need to be developed to monitor the effects of this novel class of antineoplastic agents.