[^18F] Fluoromisonidazole (FMISO) is a radiopharmaceutical used in positron emission tomography (PET) imaging to assess tissue hypoxia. It selectively accumulates in regions of low oxygen tension within tumors, providing valuable information about tumor biology, aggressiveness, and response to therapy.
FMISO is a nitroimidazole derivative that undergoes bioreduction in hypoxic environments. In areas of low oxygen tension, such as within tumors, FMISO is reduced by intracellular enzymes to form reactive intermediates that become trapped within cells. The fluorine-18 radionuclide emits positrons that can be detected by PET scanners, allowing for the visualization and quantification of hypoxic regions in tissues.
FMISO PET imaging has several clinical applications in oncology:
Identification of Hypoxic Regions: FMISO PET imaging identifies areas of low oxygen tension within tumors, which are associated with resistance to radiation therapy and chemotherapy.
Prognostication: High levels of tumor hypoxia measured by FMISO PET are associated with poor prognosis and aggressive tumor behavior in various malignancies.
Radiation Therapy: FMISO PET helps delineate hypoxic regions within tumors, guiding the delivery of targeted radiation therapy. Hypoxic areas are less sensitive to radiation and may require higher doses for effective treatment.
Chemotherapy: Tumor hypoxia assessed by FMISO PET may influence the selection of chemotherapy regimens, as hypoxic tumors are often resistant to certain chemotherapeutic agents.
Radiotherapy: Changes in tumor hypoxia measured by FMISO PET during the course of radiotherapy may indicate treatment response or resistance. Adaptive radiotherapy strategies can be implemented based on FMISO PET findings to optimize treatment outcomes.
Chemotherapy: FMISO PET imaging can assess changes in tumor hypoxia following chemotherapy, providing insight into treatment efficacy and guiding treatment adjustments.
Direct Measurement of Tumor Hypoxia: FMISO PET provides a direct measure of tissue oxygenation, allowing for precise assessment of tumor hypoxia.
Non-Invasive and Quantitative: PET imaging provides non-invasive, quantitative assessment of tumor hypoxia, enabling accurate characterization of tumor biology and response to therapy.
Comprehensive Imaging: FMISO PET provides whole-body imaging, allowing for the evaluation of hypoxic regions in primary tumors as well as metastatic lesions.