Cancer in Patients With Incidental Asymmetric Oropharynx Positron Emission Tomography Uptake

Abstract

Importance: Asymmetric oropharynx uptake on positron emission tomography (PET)/computed tomography (CT) is a common incidental finding and often prompts otolaryngology referral to rule out malignancy; however, the true risk of malignancy based on this finding is unknown.

Objective: To identify the incidence of oropharynx cancer in patients with incidental asymmetric oropharynx PET uptake.

Design, setting, and participants: In this retrospective cohort study, patients 18 years and older undergoing PET/CT scans at Mayo Clinic between January 2001 and December 2018 were included. Patients with a history or pretest suspicion of oropharynx cancer were excluded. Data were analyzed from March 2021 to December 2023.

Exposure: Blinded radiologic review of imaging studies, including measurement of maximum standardized uptake values (SUVmax) of the ipsilateral side of concern and contralateral side. Retrospective medical record review for associated clinical data.

Main outcomes and measures: The primary study outcome was the incidence of oropharynx cancer diagnosis in patients with asymmetric oropharynx PET uptake. The primary outcome was formulated before data collection.

Results: Of the 1854 patients identified with asymmetric oropharynx PET uptake, 327 (17.6%) met inclusion criteria. Of these, 173 (52.9%) were male, and the median (range) age was 65.0 (24.8-90.7) years. The mean (SD) follow-up interval was 52.1 (43.4) months. A total of 18 of 327 patients (5.5%) were newly diagnosed with oropharynx cancer. The most common diagnosis was squamous cell carcinoma (n = 9), followed by lymphoma (n = 8), and sarcoma (n = 1). Patients with an incidental diagnosis of oropharynx cancer had higher mean (SD) ipsilateral SUVmax (8.7 [3.7] vs 5.3 [1.9]) and SUVmax ratio (3.0 [1.6] vs 1.6 [0.6]) compared with patients with normal examination findings. SUVmax ratio and difference were found to be good discriminators of oropharynx cancer, with areas under the receiver operating characteristic curve of 86.3% (95% CI, 76.4-94.6) and 85.8% (95% CI, 74.8-94.6), respectively. Patients with a new diagnosis of oropharynx cancer were more likely to have a corresponding CT abnormality than those with normal examination findings (6 of 18 [33%] vs 24 of 295 [8.1%]). Patients with concerning lesions on oropharynx palpation by an otolaryngology health care professional were significantly more likely to be diagnosed with oropharynx cancer compared with patients with normal examination findings (odds ratio, 28.4; 95% CI, 6.6-145.8).

Conclusions and relevance: In this cohort study, while incidental asymmetric oropharynx PET uptake was common, a new diagnosis of oropharynx cancer was not and potentially results in a large volume of unnecessary referrals and work-up. Using SUVmax ratio, SUVmax difference, and CT correlation may increase the benefit of referral. Patients with a palpable oropharynx lesion and asymmetric oropharynx PET uptake should undergo confirmatory biopsy.

Figure 1.. Incidental Asymmetric Fluorine-18 Fluorodeoxyglucose (¹⁸F-FDG) Uptake in the Oropharynx

A, A new incidental diagnosis of oropharyngeal malignancy was made in a man in his late 60s, scanned to assess non-Hodgkin lymphoma treatment response. Positron emission tomography (PET) axial imaging, low-dose noncontrast computed tomography (CT) imaging, and rainbow-color fusion of the PET/CT demonstrate asymmetrically increased ¹⁸F-FDG uptake in the left oropharynx, with an ipsilateral maximum standardized uptake value (SUVmax) of 9.3 (blue circle), a contralateral SUVmax of 3.5 (red circle), and an abnormal lesion on CT (white arrow). The SUVmax values result in an SUVmax ratio of 2.7 and SUVmax difference of 5.8, both greater than the cut point threshold of approximately 2.0. A new diagnosis of squamous cell carcinoma in the left oropharynx was confirmed on pathology. B, Benign asymmetric uptake was found in another man in his late 60s scanned to evaluate an indeterminate pulmonary nodule. PET axial imaging, low-dose noncontrast CT imaging, and rainbow-color fusion of the PET/CT demonstrated asymmetrically increased ¹⁸F-FDG uptake in the right oropharynx, with an ipsilateral SUVmax of 5.8 (blue circle), a contralateral SUVmax of 4.1 (red circle), and no abnormal lesion visible on CT. The SUVmax ratio of 1.4 and SUVmax difference of 1.7 were below the cut point threshold of 2.0. The uptake in the right oropharynx was found to be benign, and no evidence of oropharyngeal malignancy was detected after more than 10 years of clinical follow-up.

Figure 2.. Distribution of Maximum Standardized Uptake Value (SUVmax) Measurements

A, Boxplots of univariable distribution of SUVmax measurements. B, Boxplots of SUVmax measurements broken out by incidental diagnosis of oropharyngeal cancer. SUVmax ratio was defined as the ratio of ipsilateral SUVmax to contralateral SUVmax. SUVmax difference was defined as the ipsilateral SUVmax minus the contralateral SUVmax. The midline indicates the median; the box, IQR; whiskers, 1.5-fold the IQR; and data points, outliers.

Figure 3.. Receiver Operating Characteristic Curves for Maximum Standardized Uptake Value (SUVmax) Measurements

Receiver operating characteristic curves for relationships of ipsilateral SUVmax (A), contralateral SUVmax (B), SUVmax ratio (C), and SUVmax difference (D) with incidental diagnosis of oropharyngeal cancer. AUC indicates area under the receiver operating characteristic curve.