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Hypoxia

Hypoxia in Soft-Tissue Sarcomas on [ 18 F]-Fluoroazomycin Arabinoside Positron Emission Tomography (FAZA-PET) Powerfully Predicts Response to Radiotherapy and Early Relapse. Kenneth Khamly , Peter Choong, Samuel Ngan, Rodney Hicks, Guy Toner, Jayesh Desai, Dianne Saward and David Thomas

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Hypoxia

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  1. Hypoxia in Soft-Tissue Sarcomas on [18F]-Fluoroazomycin Arabinoside Positron Emission Tomography (FAZA-PET) Powerfully Predicts Response to Radiotherapy and Early Relapse Kenneth Khamly, Peter Choong, Samuel Ngan, Rodney Hicks, Guy Toner, Jayesh Desai, Dianne Saward and David Thomas Peter MacCallum Cancer Centre, Melbourne, Australia CTOS 14th Annual Meeting November 13 – 15, 2008 London

  2. Hypoxia • Linked to various biologic changes • HIF-1α, GLUT, hexokinase, VEGF, PI3K/AKT, p53 etc. • Has been related to • Poor prognosis • Progression to a more malignant phenotype • Resistance to therapy

  3. CA-9 Glut-1 Ki-67 CD-31 VEGF-A VEGF-C

  4. Functional Imaging of Hypoxia • Most studies to date utilize O2 electrode measurements • Sampling limitations • Positron emission tomography • Non-invasive, allows evaluation of the whole tumour • [18F]-Fluoromisonidazole (F-MISO) • [18F]-Fluoroazomycin arabinoside (FAZA) • Marginally lower uptake and sensitivity • pO2≤ 10 mmHg • Faster reduction of non-specific binding

  5. Study Rationale • Hypoxia is associated with resistance to RT • Angiogenesis inhibitors have the potential to modify tumour vasculature and hypoxia • Although single agent activity is generally limited • Combination with RT is potentially interesting. • In preparation for an interventional study, this baseline study was performed to evaluate hypoxia and resistance to radiotherapy in resectable STS

  6. Objectives • Primary objectives • Proportion of STS with hypoxia on functional imaging • Secondary objectives • Correlation with response • Correlation with molecular markers

  7. Eligibility Criteria • Histologically confirmed STS • Surgically resectable disease • Suitable for neoadjuvant radiotherapy

  8. Results (1) • 23 patients (17 with FAZA-PET) • 15 Female; 8 Male • Age 35 – 81 (median 61) • Histology • MFH / High grade pleomorphic sarcoma – 43% • Liposarcoma – 30% • Other – 26% • Mean tumour size – 88 ± 8.8 mm

  9. Results (2) • Median follow-up just over 12 months • Two patients have died • Two patients developed metastases on completion of RT and prior to surgery • Five further patients have relapsed

  10. Results (3) • Response Rates • RECIST – RR 14% (SD 57%; PD29%) • FDG-PET – RR 32% (SD 47%; PD 21%) • Histology – RR 31%

  11. FAZA-PET • Hypoxia defined using tumour-to-background ratio (TBR) • TBR ≥ 1.2 classed as hypoxic (range 1.01 – 2.69) • 8/17 (47%) patients had evidence of hypoxia • Strongly associated with outcomes • None had a good histological response at resection • Lower RR and greater incidence of disease progression on RT • Predicts early relapse (< 6 months)

  12. Hypoxia on FAZA-PET • Of patients with hypoxia on FAZA-PET • 63% progressed on RT • (cf. 13% in patients without hypoxia; p=0.015) • 86% progressed on RT and/or relapsed within 6 months • (cf. 27% in patients without hypoxia; p=0.010)

  13. Plasma VEGF • VEGF-A and -C levels strongly correlated with each other • Absolute levels of VEGF-C ~ x1 log. order higher than VEGF-A

  14. p = 0.015 p = 0.017

  15. FAZA-PET Examples

  16. Case 1

  17. FAZA-PET

  18. Comparison of FDG and FAZA Scans

  19. Post Treatment FDG-PET

  20. Histological Response

  21. Case 2

  22. Comparison of PET Scans FDG Baseline FAZA Post-RT FDG

  23. Summary & Conclusions (1) • Hypoxia on FAZA-PET • is present in a significant proportion of STS • is strongly associated with clinical outcomes • resistance to radiotherapy • early relapse • Plasma VEGF-A may be a promising marker for response • Change in VEGF-A levels with radiotherapy is predictive of response • Hypoxic tumours were associated with lower baseline levels of VEGF-A (and possibly VEGF-C), and a subsequent rise in response to RT

  24. Summary & Conclusions (2) • Hypoxia and vascular changes are promising therapeutic targets for improving outcomes in STS • Study evaluating the impact of angiogenesis inhibitors in modifying hypoxia during RT for STS is currently underway

  25. David Thomas Guy Toner Peter Choong Samuel Ngan Jayesh Desai Gerard Powell Sarat Chander Julie Chu Lisa Orme Rodney Hicks David Binns Stuart Galloway John Slavin Acknowledgements • Richard Young • Samantha Cauberg • Dianne Saward • Marianne Griffin • Haematology and Oncology Targeted Therapies (HOTT) Research Fellowship • Clinical Oncological Society of Australia (COSA) • Medical Oncology Group of Australia (MOGA) • Haematology Society of Australia and New Zealand (HSANZ) • Roche Pty Ltd

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