Usefulness of 11C-Methionine Positron Emission Tomography for Differentiating Tumor Recurrence and Necrosis in Ethmoid Sinus Cancer With Intracranial Extension

For head and neck cancer, treatment efficacy and recurrence are often assessed by morphological imaging methods such as CT and MRI. However, these techniques are sometimes ineffective for distinguishing qualitative changes in tumors following treatment. Here, we report the case of a 50-year-old male patient who received chemoradiotherapy for head and neck squamous cell carcinoma with intracranial extension. Following treatment, the patient's symptoms subsided, and MRI at two and six months demonstrated tumor shrinkage. Six months after treatment, fluorodeoxyglucose (FDG) positron emission tomography (PET) revealed changes in the intracranial lesions, which were difficult to distinguish between tumor recurrence and necrosis. Consequently, we used 11C-methionine (MET) PET during follow-up. The findings from MET PET showed no evidence of disease recurrence; thus, the lesions were subsequently monitored for necrotic changes. This case suggests the potential utility of MET PET for differentiating recurrence from necrosis in head and neck cancers with intracranial extension. Further studies with larger cohorts are warranted to clarify its diagnostic accuracy and establish appropriate evaluation criteria.