Hypoxia in solid
tumors is one of the seminal mechanisms for developing aggressive trait and treatment resistance in solid
tumors. This evolutionarily conserved biological mechanism along with derepression of cellular functions in
cancer, although resulting in many challenges, provide us with opportunities to use these adversities to our advantage. Our ability to use molecular imaging to characterize therapeutic targets such as
hypoxia and apply this information for therapeutic interventions is growing rapidly. Evaluation of
hypoxia and its biological ramifications to effectively plan appropriate
therapy that can overcome the cure-limiting effects of
hypoxia provides an objective means for treatment selection and planning.
Fluoromisonidazole (
FMISO) continues to be the lead
radiopharmaceutical in PET imaging for the evaluation, prognostication, and quantification of tumor hypoxia, one of the key elements of the tumor microenvironment.
FMISO is less confounded by blood flow, and although the images have less contrast than FDG-PET, its uptake after 2 hours is an accurate reflection of inadequate regional
oxygen partial pressure at the time of
radiopharmaceutical administration. By virtue of extensive clinical utilization,
FMISO remains the lead candidate for imaging and quantifying
hypoxia. The past decade has seen significant technological advances in investigating
hypoxia imaging in
radiation treatment planning and in providing us with the ability to individualize radiation delivery and target volume coverage. The presence of widespread
hypoxia in the
tumor can be effectively targeted with a systemic hypoxic cell
cytotoxin or other agents that are more effective with diminished
oxygen partial pressure, either alone or in combination. Molecular imaging in general and
hypoxia imaging in particular will likely become an important in vivo imaging
biomarker of the future, complementing the traditional direct tissue sampling methods by providing a snap shot of a primary
tumor and metastatic disease and in following treatment response and will serve as adjuncts to personalized
therapy.