Incidental findings on 18-FDG PET-CT in head and neck cancer. A retrospective case-control study of incidental findings on 18-FDG PET-CT in patients with head and neck cancer.

Purpose: Use of 18-FDG PET-CT is increasing in patients with head and neck cancer, enabling the identification of metastases or synchronous malignancies, but also 'incidental' disease. We aimed to establish the rate of 'incidental' findings resulting from 18-FDG PET-specific imaging, that would not have been otherwise identified on other imaging, in patients with head and neck cancer undergoing staging or surveillance of disease.

Methods: 18-FDG PET-CT was performed for investigation or surveillance. Case notes were reviewed retrospectively. Unexpected findings identifiable on CT imaging alone, or by FDG-PET were recorded. For those only identifiable with FDG-PET, findings were divided into either 'incidental' or 'intentional', and benign or malignant.

Results: 93 patients underwent 18- FDG PET-CT. 86.0% had new pathology identified. 3.2% had a new malignancy identified. 37.6% had new findings on FDG-PET that would not have been identified on CT alone: 5.4% had 'intentional findings' (metastasis), and 32.3% had 'incidental findings' (synchronous malignancy or benign). 1.1% had a new malignancy on FDG-PET alone.

Conclusions: Intentional and incidental findings are likely on 18-FDG PET-CT. Whilst important for patient management, there is an associated emotional and financial cost, which needs acknowledgement and further investigation.