Hypoxia PET/CT and colorectal cancer: a case report

Introduction: Colorectal cancer risk stratification traditionally focuses on tumor node metastasis staging. Seemingly equivalent tumors can differ unpredictably in prognosis; more sophisticated quantification and stratification methods are required to identify tumors with a high likelihood of becoming metastatic. Hypoxia (low oxygen concentration) is associated with aggressive phenotypes and poor prognosis. Hypoxia is associated with treatment resistance consequently there is an unmet clinical requirement to develop personalised treatment based on hypoxia. Positron emission tomography/computed tomography (PET/CT) imaging can non-invasively detect hypoxic tumors. [18F]Fluoroazomycin arabinoside ([18F]FAZA) is a leading hypoxia PET/CT radiotracer, and uptake is associated with lower disease free survival. Case Report: A 78-year-old man, diagnosed with a localised colorectal cancer, underwent [18F]FAZA PET/CT imaging pre-operatively. This confirmed hypoxic regions in the tumor with correlation demonstrated with carbonic anhydrase IX (CAIX) immunohistochemistry (IHC). He underwent a right hemicolectomy. The pathological staging for his colorectal cancer predicted a good outcome; thus, he did not receive adjuvant chemotherapy. The patient subsequently developed early metastatic disease with two lung metastases, which were resected by thoracotomy and wedge resection. He continues on follow up at present with no evidence of recurrent disease. Conclusion: Hypoxia can be an important marker in colorectal cancer when determining risk and prognosis. We present evidence of clinical correlation of FAZA uptake and CAIX IHC in colorectal cancer, a key aspect in FAZA tracer validation. PET/CT potentially provides a specific tool for stratification for hypoxia-related treatment modification and development of hypoxia biomarkers.