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Images in thorax
18F-Misonidazole PET-CT scan detection of occult bone metastasis
  1. Daniel R McGowan1,2,
  2. Ruth E Macpherson3,
  3. Kevin M Bradley3,
  4. John D Fenwick1,
  5. Fergus V Gleeson1,3,
  6. Geoff S Higgins1
  1. 1Department of Oncology, University of Oxford, Oxford, UK
  2. 2Radiation Physics and Protection, Oxford University Hospitals NHS Trust, Oxford, UK
  3. 3Department of Radiology, Oxford University Hospitals NHS Trust, Oxford, UK
  1. Correspondence to Daniel R McGowan, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK; daniel.mcgowan{at}oncology.ox.ac.uk

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A 67-year-old man with locally advanced non-small cell lung cancer entered a phase I trial combining a novel phosphoinositide 3-kinase inhibitor (BKM120) with palliative radiotherapy.1 The trial uses 18F-misonidazole (FMISO) positron emission tomography (PET)-CT imaging to assess any changes in tumour hypoxia. FMISO is a tracer currently only used in the research setting.

A pretreatment FMISO PET-CT scan identified an occult, asymptomatic scapular metastasis (figure 1) undetectable on routine CT imaging (figure 2A). This was subsequently confirmed on MRI imaging. The patient was referred for palliative chemotherapy upon completing the trial. To our knowledge, this is the first published report of FMISO PET-CT detecting an occult metastasis. The FMISO image (figure 1) also shows hypoxia within mediastinal nodes. The enlarged nodes were seen on the routine CT imaging (figure 2B) unlike the occult scapular metastasis.

Figure 1

18F-Misonidazole positron emission tomography (PET) image fused with the corresponding CT displayed on a tumour-to-blood ratio (TBR) colour scale. Red regions depict a TBR >1.4, indicating hypoxia, and no visible PET depicts a TBR <1, indicating normoxia.3 This axial image shows the unexpected hypoxic bone metastasis indicated by the white arrow in addition to hypoxic nodal disease in the mediastinum.

Figure 2

CT contrast-enhanced image reformatted using 1.25 mm axial thickness for (A) a bone reconstruction showing that the bone metastasis visible on 18F-misonidazole (FMISO) positron emission tomography (PET) is not visible on CT and (B) standard reconstruction showing the enlarged mediastinal nodal disease shown to be hypoxic on the FMISO PET.

FMISO is reduced and retained in hypoxic tissue and so allows the identification of hypoxic volumes. Tumour hypoxia is associated with marked resistance to radiotherapy and poor clinical outcomes.2 There is significant interest in using FMISO PET-CT to monitor changes to tumour hypoxia arising from drug or radiotherapy treatment. FMISO images also identify hypoxic volumes of the tumour that may benefit from boosting the radiation dose. This image illustrates that small tumour volumes may harbour clinically relevant regions of hypoxia.

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Footnotes

  • Contributors All authors wrote, revised and approved the final manuscript.

  • Funding The trial was supported by Cancer Research UK (CRUKD/12/016), the National Institute of Health Research (NIHR), Health Education England (HEE), the Oxford ECMC, the CRUK EPSRC Oxford Cancer Imaging Centre, the CRUK Oxford Centre and Novartis.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval Oxford REC.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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