Is There a Role for PET/CT Parameters to Characterize Benign, Malignant, and Metastatic Parotid Tumors?

Abstract

OBJECTIVE Assessment of benign and malignant lesions of the parotid gland, including metastatic lesions, is challenging with current imaging methods. Fluorine-18 FDG PET/CT is a noninvasive imaging modality that provides both anatomic and metabolic information. Semiquantitative data obtained from PET/CT, also known as PET/CT parameters, are maximum, mean, or peak standardized uptake values (SUVs); metabolic tumor volume; total lesion glycolysis; standardized added metabolic activity; and normalized standardized added metabolic activity. Our aim was to determine whether FDG PET/CT parameters can differentiate benign, malignant, and metastatic parotid tumors. MATERIALS AND METHODS Thirty-four patients with parotid neoplasms underwent PET/CT before parotidectomy; maximum SUV, mean SUV, peak SUV, total lesion glycolysis, metabolic tumor volume, standardized added metabolic activity, and normalized standardized added metabolic activity were calculated on a dedicated workstation. Univariate analyses were performed. A ROC analysis was used to determine the ability of PET/CT parameters to predict pathologically proven benign, malignant, and metastatic parotid gland neoplasms. RESULTS Fourteen patients had a benign or malignant primary parotid tumor. Twenty had metastases to the parotid gland. When the specificity was set to at least 85% for each parameter to identify cut points, the corresponding sensitivities ranged from 15% to 40%. Assessment of benign versus malignant lesions of parotid tumors, as well as metastasis from squamous cell carcinoma versus other metastatic causes, revealed that none of the PET/CT parameters has enough power to differentiate among these groups. CONCLUSION PET/CT parameters, including total lesion glycolysis, metabolic tumor volume, standardized added metabolic activity, and normalized standardized added metabolic activity, are not able to differentiate benign from malignant parotid tumors, primary parotid tumors from metastasis, or metastasis from squamous cell carcinoma and nonsquamous cell carcinoma metastasis.

Management of Salivary Gland Malignancy: ASCO Guideline

“…66 There are numerous caveats with this recommendation including an awareness that some salivary malignancies do not have high FDG uptake and many benign tumors including Warthin and benign mixed tumors are FDG-avid. 145,243 Recommendation 1.5. Providers should perform a tissue biopsy (either FNAB or CNB) to support distinction of salivary gland cancers from nonmalignant salivary lesions (Type: evidence based; Evidence quality: high; Strength of recommendation: strong).…”

Contemporary Management of Benign and Malignant Parotid Tumors

“…Like for extended diagnostics for benign tumors, CT should be used for further staging if MRI is not available or contraindicated. Fluorine-18 FDG PET/CT is not helpful to differentiate benign, malignant, and metastatic parotid tumors ( 33 ). PET/CT parameters, including total lesion glycolysis, metabolic tumor volume, standardized added metabolic activity, and normalized standardized added metabolic activity, are not able to differentiate benign from malignant parotid tumors, primary parotid tumors from metastasis, or metastasis from squamous cell carcinoma and non-squamous cell carcinoma metastasis.…”

Controversies in the Workup and Surgical Management of Parotid Neoplasms

“…21 Positron emission tomography is less frequently used in salivary cancers as the degree of avidity does not reliably correlate with the malignant potential of the lesion. [22][23][24] However, recent evidence suggests that uptake heterogeneity within lesions may correlate with parotid cancers. 25 For advanced primary tumors and those with pathologic adenopathy, chest imaging should be obtained, usually in the form of a dedicated chest CT.…”