Tissue oxygen tension measurements in the Shionogi model of prostate cancer using 19F MRS and MRI
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Objectives: To investigate changes in tumour tissue oxygenation throughout the tumour growth–regression–relapse cycle in an androgen-dependent animal tumour model. Materials and methods: 19F T1 relaxometry of Perfluoro-15-Crown-5-Ether was used to measure in vivo partial oxygen pressure (pO2) of Shionogi tumours on a 2.35-T MR scanner. Perfluoro-15-Crown-5-Ether was administered as an emulsion injected intravenously or as a neat compound injected directly into the tumour. Non-localized, tumour 19F T1 measurements, made at multiple time points throughout the tumour cycle, were translated into pO2 levels. Results: No correlation between tumour size and pO2 values was found. Values of pO2 for growing tumours (50 ± 30 torr) were significantly lower than for regressing and relapsing tumours after 9 days post-castration (70 ± 10 torr, p<0.05). Maximum pO2 values (90 ± 30 torr) were reached between fifth and eighth day post-castration, when tumour pO2 was significantly higher than both pre-castration (p<0.001) and after 9 days post-castration (p<0.05). Conclusion: We demonstrate that longitudinal pO2 measurements in vivo are feasible. Values of pO2 for growing androgen-dependent tumours were significantly lower than for regressing and relapsing androgen-independent tumours. These results have potential clinical importance in optimizing the timing of chemotherapy and/or radiotherapy of hormone dependent tumours.
Keywords19F NMR pO2 measurements Shionogi tumour model Hormone sensitive tumours
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The authors thank Ms. Mary Bowden from the Prostate Centre at VGH for her excellent technical support. Generous help of Fresenius-Kabi, Clayton, NC, USA in the preparation of the PFC emulsion is gratefully acknowledged. This work was supported by research grants from Health Canada and Terry Fox Foundation.
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