SU-C-204-05: Magnetic Resonance-Induced Adaptive Response to Orthovoltage Radiation Therapy in FSa and SA-NH Mouse Tumor Cell Lines.

PURPOSE: To assess the effect of pre-treatment Magnetic Resonance Imaging (MRI) on cell survival following orthovoltage radiation therapy.

METHODS: This in vitro study examined the survival of FSa cells (extracted from methylcholanthrene-induced fibrosarcoma in the flank of a C3H female mouse) and SA-NH cells (derived from a spontaneously arising murine sarcoma tumor) having undergone an MRI scan prior to radiation exposure. Cell cultures were kept at 37 C, in a humidified environment with 5% CO2, and were grown to confluence prior to the start of the experiment. Each cell culture underwent two, 25 minute MRIs spaced 24 hours apart using a standard brain imaging protocol. The cultures were exposed to a 2 Gy dose of radiation beginning 15 minutes after the end of each MRI scan. Irradiations were performed by a Philips RT250 X-ray generator at 250 kVp and 15 mA. All MR imaging was performed on a 1.5 T Philips Achieva scanner using a head and neck vasculature coil.

RESULTS: Cells given an MRI scan prior to radiation exhibited an increase in mean surviving fraction of 10.8% and 9.6% in FSa and SA-NH cells, respectively. The difference was found to be statistically significant in both cell types by a student two-tailed t test with P = 0.011 and P < 0.001 for FSa and SA-NH, respectively.

CONCLUSION: MRI may cause an increase in radio-resistance in FSa and SA-NH cells. If this biological effect is found to be consistent across other cell types and voltage ranges, these results could help inform treatment planning by improving our understanding of the joint effects of MRI and ionizing radiation. This work was supported in part under NIH grant numbers T32 EB002103, NCI R01-CA 132998, DOE Low Dose Program/Project Grant DE-413 SC0001271. DJ Grdina is a paid consultant to Pinnacle Biologics. DJ Grdina and JS Murley are minority equity partners in Pinnacle Oncology LLC.