Utility of quantitative 18 F-fluorodeoxyglucose uptake measurement to identify occult tonsillar carcinoma in patients with cervical metastasis of unknown primary tumours: a retrospective case-control study

Risk of malignancy in incidental oropharyngeal lesions exhibiting fluorodeoxyglucose uptake which proceed to tissue biopsy

BACKGROUND

Utilization of positron emission tomography/computed tomography (PET/CT) with fluorodeoxyglucose is increasing in use for a variety of indications, including surveillance of cancer patients. There is a paucity of evidence pertaining to the significance of incidental PET-avid oropharyngeal lesions. This study aims to examine the clinical and radiological features of these incidental oropharyngeal lesions in patients undergoing PET for indications other than head and neck cancer.

METHODS

Retrospective cohort study of three Australian tertiary hospitals, from 2015 to 2021, on adult patients undergoing biopsy of incidental PET-avid oropharyngeal lesions. Primary outcome of interest was the incidence of malignancy. Patients with a previous history of, or undergoing investigations for, head and neck cancer were excluded.

RESULTS

Thirty-one patients were included, wherein 21 patients had tonsillar uptake, and 13 patients had base of tongue uptake. Tonsillar disease was mostly asymmetrical (n = 15/21), bilateral (n = 11/21), and had median SUVmax 9.35 (n = 12, IQR 7.4-11.15). Base of tongue was mostly asymmetrical (n = 7/13, 54%), bilateral (n = 8/13, 62%), and had median SUVmax 8.2 (n = 10, IQR 6.9-12.65). Seven patients had malignancy confirmed on tissue biopsy: five biopsies confirmed the tissue diagnosis of suspected lymphoma, and two incidental findings of unexpected malignancies: one p16 positive tonsillar squamous cell carcinoma, and one metastatic breast cancer.

CONCLUSION

In 31 patients undergoing tissue biopsy for incidental PET-avid oropharyngeal lesions, there were two unexpected malignancies. Our study results indicate that although unexpected malignancies are uncommon, a malignant diagnosis cannot be excluded from clinical features alone.

Incidental FDG-Avid Focuses in Palatine Tonsils on PET/CT

OBJECTIVES

The management of incidental findings of FDG-avid tonsils on PET/CT (IFT) is unclear. We aimed to explore the prevalence of malignancy in IFT, identify risk factors for malignancy, and calculate optimal cutoffs of maximum standardized uptake values (SUV_max ) to discriminate between benign and malignant lesions.

METHODS

All patients who were tonsillectomized at our institution because of IFT from October 2011 to December 2020 were included. Patients undergoing PET/CT due to suspected tonsillar disease or cancer of unknown primary were excluded.

RESULTS

In total, 77 patients were included, of which 11 (14%) of them had IFT malignancy. Dysphagia (p = 0.019) and alcohol abuse (p = 0.035) were associated with malignancy. Absolute SUV_max cutoff (≥9: sensitivity 100%; specificity 53%) was superior to SUV_max side-to-side ratio (≥1.5: sensitivity 64%; specificity 70%) to discriminate between benign and malignant lesions.

CONCLUSION

We recommend tonsillectomy for patients with IFT displaying SUV_max  ≥ 9.0, ratio ≥ 1.5, or symptoms or findings suggesting malignancy.

LEVEL OF EVIDENCE

3 Laryngoscope, 132:2370-2378, 2022.

Clinical Significance of Increased FDG Uptake in the Waldeyer Ring and the Nasopharynx Region Identified by PET-CT in Postchemotherapy Follow-up in Patients With Lymphoma: When Should We Perform Biopsy?

PURPOSE

To identify whether fluorodeoxyglucose (FDG) uptake in the Waldeyer ring (WR)/nasopharyngeal (NP) region by positron emission tomography-computed tomography (PET-CT) was physiologic or pathologic in the follow-up of lymphoma patients receiving postchemotherapy treatment.

PATIENTS AND METHODS

We retrospectively examined FDG uptake in the WR/NP region in 534 patients with lymphoma as assessed by PET-CT used for both diagnosis and follow-up.

RESULTS

Forty-nine patients had FDG uptake in the WR/NP region by PET-CT performed after completion of a chemotherapy regimen. Biopsy was performed for 11 of these patients in whom the uptake was considered to be pathologic, and results indicated the presence of reactive follicular hyperplasia. It was considered to be physiologic in 38 patients. PET-CT was repeated after 1 year, and no significant difference was identified between the standardized maximum uptake values (SUV_max; P = .107). The initial diagnosis of 20 patients was made via biopsy performed in the WR/NP region. The SUV_max for the FDG uptake in these patients, asymmetry, SUV_max of the coexisting lymphadenopathies in the neck, and FDG uptake with a counterpart finding by CT were significantly higher than other groups (P = .047, .001, and .005).

CONCLUSION

When deciding whether to resample after treatment completion, it should be taken into account that, in addition to the SUV_max of the lesion, asymmetry, and the SUV_max of the coexisting lymphadenopathy in the neck, a crucial criterion is whether the FDG uptake has a counterpart finding by CT.

PET/CT Evaluation of Head and Neck Cancer of Unknown Primary

The diagnosis of carcinoma of unknown primary in the head and neck is made when there is a metastasis but no primary lesion is identified after physical exam and diagnostic CT or MR imaging. PET/CT is the first step in searching for a primary lesion, followed by more invasive techniques such as endoscopy and surgery. Knowledge of the different tumor histologic types, preferential locations of nodal spread, imaging pitfalls, and other special considerations such as cystic metastases can be helpful in the ultimate identification of primary tumors, which leads to improved overall patient survival.

Palatine tonsil SUVmax on FDG PET-CT as a discriminator between benign and malignant tonsils in patients with and without head and neck squamous cell carcinoma of unknown primary

AIM

To analyse the maximum standardised uptake value (SUVmax) ratio between tonsils in patients with and without tonsillar carcinoma to determine useful diagnostic thresholds.

MATERIALS AND METHODS

Positron-emission tomography (PET)/computed tomography (CT) examinations of patients with suspected head and neck squamous cell carcinoma (SCC) and controls from April 2013 to September 2016 were reviewed retrospectively. Tonsillar SUVmax ratios (ipsilateral/contralateral for malignant tonsils, maximum/minimum for patients without [controls]) were calculated and used to construct a receiver operating characteristic (ROC) curve.

RESULTS

Twenty-five patients had tonsillar carcinoma (mean SUVmax ratio of 2, range 0.89-5.4) and 86 patients acted as controls (mean SUVmax ratio of 1.1, range 1-1.5). Using the ROC, the most accurate SUVmax ratio for identifying malignancy was >1.2 (77% sensitivity, 86% specificity). A potentially more clinically useful SUVmax ratio is ≥1.6 with 62% sensitivity and 100% specificity.

CONCLUSION

An SUVmax ratio between tonsils of ≥1.6 is highly suspicious for SCC and could be used to direct site of biopsy. Some malignant tonsils had normal FDG uptake; therefore, PET/CT should not be used to exclude tonsillar cancer. Minor asymmetrical uptake is frequently seen in non-malignant tonsils and does not necessarily require further investigation. Due to the single centre nature of this study and the recognised variation in SUV measurements between PET scans, other centres may need to develop their own cut-offs.

Evidence-based management of incidental focal uptake of fluorodeoxyglucose on PET-CT

Focal incidental uptake, with or without CT abnormalities, is a common finding on fluorodeoxyglucose PET/CT and evidence-based management for this type of uptake is lacking. This article reviews the evidence on focal incidental uptake including the incidence of malignancy, differential diagnosis and imaging criteria which can be used to further characterize it. The article focusses on PET rather than CT criteria. The strength of the evidence base is highly variable ranging from systematic reviews and meta-analyses to a virtual absence of evidence. Caution needs to be used when using standardized uptake values (SUVs) reported in other studies due to interpatient and institution observed variation in SUVs. There is sufficient evidence to permit specific suggestions on how to interpret the foci and recommend further management in the: pituitary (investigate when SUVmax >4.1), thyroid (investigate all), breast (investigate all), lung parenchyma (if focus of fluorodeoxyglucose without a CT nodule, no further investigations), colon (investigate all foci with SUVmax >5.9, urgently if SUVmax >11.4), adrenals (criteria depend on if patient has cancer) and prostate gland (investigate in males aged >50 years or >40 years if peripheral uptake or patient has other risk factors). There is some evidence to guide further management for the parotid gland, naso-orophaynx, oesophagus, pancreas, uterus and ovaries. There is insufficient evidence to guide management for the liver, spleen, kidneys, gallbladder, testis and bone, for these organs patient characteristics and other guidelines will likely be of more use in determining further management.

The role of PET/CT in the management of patients affected by head and neck tumors: a review of the literature

The management of head and neck tumor (HNSCC) has been changing over the years, especially due to the aid of imaging techniques that help physicians to attain a correct diagnosis. These techniques represent a valuable tool to help tailor treatment and during follow-up of patients affected by malignancies. The aim of this review is to summarize the results of the most recent and relevant studies about the use of PET imaging in HNSCCs. This review is divided into six chapters: (1) The role of PET/CT in the pre-treatment phase; (2) PET/CT and radiotherapy planning; (3) PET/CT in the post-treatment setting; (4) PET/CT and SUVmax for prediction of prognosis; (5) miscellanea on the utility of PET in specific HNSCCs; (6) non-FDG PET tracers used in HNSCC. Promising results have been obtained so far. Despite the encouraging outcomes, more investigations are needed to warrant the value of this technique, especially in the pre-treatment setting.