TOLD MRI Validation of Reversal of Tumor Hypoxia in Glioblastoma with a Novel Oxygen Therapeutic
Heling Zhou1, David Wilson2, Jason Lickliter3, Jeremy Ruben4, Natarajan Raghunand5, Michael Sellenger6, Ralph P Mason7, and Evan Unger2,8

1UT Southwestern Medical Center, Dallas, TX, United States, 2NuvOx Pharma, Tucson, AZ, United States, 3Nucleus Networks, Melbourne, Australia, 4William Buckland Radiotherapy Centre, Melbourne, Australia, 5Moffitt Cancer Center, Tampa, FL, United States, 6Alfred Hospital, Prahran, Australia, 7Radiology, UT Southwestern Medical Center, Dallas, TX, United States, 8Medical Imaging, The University of Arizona, Tucson, AZ, United States

Synopsis

Glioblastoma multiforme (GBM) is known to be a hypoxic tumor and hypoxia adversely affects response to radiation therapy. Dodecafluoropentane emulsion (DDFPe) can improve oxygenation. Tissue oxygen level dependent (TOLD) MRI is an oxygen sensitive imaging technique which is used in this study to assess the improvement of oxygenation after administration of DDFPe. Two different doses were tested and each showed decreased T1 indicating improved oxygenation.

PURPOSE

Glioblastoma multiforme (GBM) is known to be a hypoxic tumor and hypoxia adversely affects response to radiation therapy. Dodecafluoropentane emulsion (DDFPe) on a weight basis, delivers over 100x as much oxygen as other higher molecular weight fluorocarbons and is under study as an oxygen therapeutic in GBM patients treated with chemoirradiation. Tissue oxygen level dependent (TOLD) MRI is an oxygen sensitive imaging technique that is being used to study tumor re-oxygenation in these patients.

Methods

With informed consent and IRB approval adult patients with GBM with residual tumor post-surgery were enrolled into the dose escalation phase of the study. Patients received DDFPe (2%w/vol DDFPe) at doses of 0.05 cc/kg, 0.1 cc/kg or 0.17 cc/kg I.V. 30-60 minutes prior to each fraction of radiation (2-Gy each, 30 fractions over 6 weeks). Temozolomide chemotherapy was given concurrently. Radiation was performed while the patients were breathing carbogen via a non-rebreathing circuit; the post-radiation MRI was performed while the patients were breathing oxygen. All patients underwent standard MR imaging at 1.5 Tesla. TOLD MRI was performed on patients at the higher two dose levels pre and post DDFPe on two separate occasions, days #1 and days #5 or 10 after initiation of radiation. Steady state free precession (SSFP) Look-Locker was used to obtain T1 maps. T1 maps were calculated from 3 axial slices obtained through tumor from either 3 or 4 repetitions.

Results

TOLD MRI showed substantial decreases in T1 of tumor tissue after dosing with DDFPe and breathing oxygen (mean T1 decreased from 1501±454 ms to 1371±35 ms on day one and 1459±326 ms to 1183±271 ms on day 5 for the patient receiving 0.1 cc/kg DDFPe; from 1511±93 ms to 1250±85 ms on day 1 and from 1454±75 ms to 1281±77 ms on day 10 for the patient receiving 0.17cc/kg DDFPe), while inconsistent changes were found in contralateral normal brain (ranging from 863 to 1144 ms for both patients at all time points). The two different doses of DDFPe showed similar effect.

Discussion and conclusion

The change in T1 (TOLD) with oxygen breathing after DDFPe administration indicated improved tumor oxygenation. The utility of TOLD MRI as a potential non-invasive prognostic imaging biomarker holds promise for precision medicine in terms of assessing tissue reoxygenation of hypoxic tumors. The ability to alter tumor oxygenation in GBM patients pre-treated with DDFPe could have important therapeutic implications.

Acknowledgements

No acknowledgement found.

References

No reference found.

Figures

Representative T1 maps of two patients pre (air breathing) and post (oxygen breathing) DDFPe injection and radiation treatments. Arrows indicate tumors.



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
3576