Orthotopic Esophageal Cancers: Intraesophageal Hyperthermia-enhanced Direct Chemotherapy in Rats

Purpose To determine the feasibility of using intraesophageal radiofrequency (RF) hyperthermia to enhance local chemotherapy in a rat model with orthotopic esophageal squamous cancers. Materials and Methods The animal protocol was approved by the institutional animal care and use committee and the institutional review board. Human esophageal squamous cancer cells were transduced with luciferase lentiviral particles. Cancer cells, mice with subcutaneous cancer esophageal xenografts, and nude rats with orthotopic esophageal cancers in four study groups of six animals per group were treated with (a) combination therapy of magnetic resonance imaging heating guidewire-mediated RF hyperthermia (42°C) plus local chemotherapy (cisplatin and 5-fluorouracil), (b) chemotherapy alone, (c) RF hyperthermia alone, and (d) phosphate-buffered saline. Bioluminescent optical imaging and transcutaneous ultrasonographic imaging were used to observe bioluminescence signal and changes in tumor size among the groups over 2 weeks, which were correlated with subsequent histologic results. The nonparametric Mann-Whitney U test was used for comparisons of variables. Results Compared with chemotherapy alone, RF hyperthermia alone, and phosphate-buffered saline, combination therapy with RF hyperthermia and chemotherapy induced the lowest cell proliferation (relative absorbance of formazan: 23.4% ± 7, 44.6% ± 7.5, 95.8% ± 2, 100%, respectively; P < .0001), rendered the smallest relative tumor volume (0.65 mm³ ± 0.15, P < .0001) and relative bioluminescence optical imaging photon signal (0.57 × 10⁷ photons per second per square millimeter ± 0.15, P < .001) of mice with esophageal cancer xenografts, as well as the smallest relative tumor volume (0.68 mm³ ± 0.13, P < .05) and relative photon signal (0.56 × 10⁷ photons per second per square millimeter ± 0.11. P < .001) of rat orthotopic esophageal cancers. Conclusion Intraesophageal RF hyperthermia can enhance the effect of chemotherapy on esophageal squamous cell cancers. ^© RSNA, 2016.