From the Guidelines
Definition of Non-FDG Avid
Non-FDG avid refers to a condition or lesion that does not show significant uptake of Fluorodeoxyglucose (FDG) on a Positron Emission Tomography (PET) scan, indicating low metabolic activity 1.
Clinical Implications
This can be seen in various conditions, such as some types of tumors, inflammatory lesions, or benign processes. For instance, a lack of FDG uptake in an adrenal nodule is considered conclusive for a benign adrenal adenoma and obviates further workup 1. However, it is essential to consider the clinical context and other imaging findings to accurately interpret the results of a PET scan, as non-FDG avid lesions may still require further evaluation or monitoring.
Key Points to Consider
- Non-FDG avid lesions do not necessarily rule out malignancy or the need for further investigation 1.
- Clinical context, including patient history and other imaging modalities like CT or MRI, is crucial for interpreting PET scan results 1.
- The absence of FDG uptake can be indicative of certain benign conditions, but its presence is not exclusive to malignant processes, as inflammatory or infectious causes can also lead to increased FDG uptake 1.
Importance of Clinical Context
In the evaluation of lymphoma, for example, new FDG-avid foci consistent with lymphoma rather than another etiology are considered indicative of disease activity, while non-FDG avid lesions may require biopsy or interval scanning for clarification 1. Therefore, understanding the significance of non-FDG avidity requires a comprehensive approach that considers both the imaging findings and the broader clinical picture.
From the FDA Drug Label
In comparison to background activity of the specific organ or tissue type, regions of decreased or absent uptake of Fludeoxyglucose F 18 reflect the decrease or absence of glucose metabolism. Depending on tumor type, stage, and location, Fludeoxyglucose F 18 accumulation may be increased, normal, or decreased.
Non-FDG (Fluorodeoxyglucose) avid means that there is decreased or absent uptake of Fludeoxyglucose F 18, reflecting decrease or absence of glucose metabolism in a specific organ or tissue type 2.
From the Research
Definition of Non-FDG Avid
- Non-FDG avid refers to lesions or tissues that do not accumulate Fluorodeoxyglucose (FDG) on positron emission tomography (PET) scans 3, 4.
- This can be due to various reasons, including the type of cancer, treatment effects, or benign conditions 5, 6.
Characteristics of Non-FDG Avid Lesions
- Non-FDG avid lesions may appear as sclerotic lesions on computed tomography (CT) scans, indicating a possible transformation of metabolically active disease into blastic metabolically inactive metastases after treatment 4.
- Non-FDG avid primary papillary thyroid carcinoma may not differ from FDG-avid papillary thyroid carcinoma in terms of clinicopathological and biological characteristics, except for tumor size and macrocalcification 6.
Clinical Significance of Non-FDG Avid Findings
- Non-FDG avid findings can be clinically significant, and routine systematic review of low-dose CT scans is required to avoid missing potentially important findings, such as pleural effusions, vascular aneurysms, and metastatic pulmonary nodules 3.
- Familiarity with common and unusual iatrogenic causes of FDG avidity can improve the accuracy of distinguishing treatment effects and complications from residual or recurrent malignancy at FDG PET/CT examinations 5.