Bioluminescence Image as a Quantitative Imaging Biomarker for Preclinical Evaluation of Cryoablation in a...

To employ bioluminescence imaging (BLI) as a quantitative imaging biomarker to assess preclinical evaluation of cryoablation in a murine model.

In vitro, Colon26-Luc (C26-Luc) cells were seeded at 6 different concentrations in 35-mm dishes. These were divided into 6 groups: group 0 (G0), a control group without treatment; and groups 1-5 (G1-G5) according to the number of freeze-thaw cycles, with each cycle consisting of freezing at -80°C for 10 min followed by thawing at room temperature for 5 minutes. BLI and flow-cytometric analysis were performed after cryotherapy. In vivo, 20 tumor-bearing mice with C26-Luc cells were divided into 4 groups: group 0 (G0), a control group; and groups 1-3 (G1-G3) according to the number of freeze-thaw cycles. Each cryoablation procedure was performed for 30 seconds with liquid nitrogen (-170°C) applied with cotton-tipped applicators. BLI was acquired at 6 hours and 1, 3, and 7 days after treatments.

In vitro, BLI signal showed a negative correlation with the number of freeze-thaw cycles (r = -0.86, P = .02). In vivo, there was no difference in tumor volume at 1 day after cryoablation among all groups, but the BLI signals were significantly different between G0 and G2/G3 (P = .03 and P = .02, respectively) and between G1 and G3 (P = .04). BLI signals reflected tumor growth speed and survival ratio.

This study demonstrates the direct validation of BLI as a quantitative tool for the early assessment of therapeutic effects of cryoablation.