Squamous cell carcinoma of the palatine tonsils: FDG standardized uptake value ratio as a biomarker to differentiate tonsillar carcinoma from physiologic uptake.

PURPOSE: To quantify fluorine 18 ((18)F) fluorodeoxyglucose (FDG) uptake in the palatine tonsils to identify a sensitive and specific metric for distinguishing physiologic asymmetric uptake from squamous cell carcinoma (SCC).

MATERIALS AND

METHODS

This HIPAA-compliant retrospective study was approved by institutional review board. Informed consent requirements were waived. Twenty-six patients (seven female, 19 male; mean age, 53.46 years + or - 10.45 [standard deviation]) with tonsillar SCC were included. Twenty-six patients (seven female, 19 male; mean age, 61.77 years + or - 10.12) with head and neck carcinomas not involving the tonsils were included as control subjects. Tonsil standardized uptake values (SUVs) were measured bilaterally in each group. Independent-samples t test was used to compare mean SUVs, and Pearson correlation was used to evaluate association of FDG uptake between tonsils within control subjects.

RESULTS

The mean maximum SUV (SUV(max)) of tonsil tumors was 9.36 + or - 4.54, which was significantly higher than that of contralateral cancer-free tonsils (2.54 + or - 0.88; P < .0001) and tonsils in control subjects (2.98 + or - 1.08; P < .0001). In patients with tonsillar cancer, the mean difference in SUV(max) between tonsils was 10.43 + or - 7.07, which was significantly greater than that in control subjects (0.62 + or - 0.54; P < .0001). The mean SUV(max) ratio between tonsils in patients with carcinoma was 3.79 + or - 1.69, which was threefold higher than in control subjects (1.18 + or - 0.13; P < .0001). For receiver operating characteristic analysis using SUV(max) ratio to differentiate benign uptake from SCC, the area under the curve was 1.00 (95% confidence interval: 1.00, 1.00). A cutoff ratio of 1.48 had 100% sensitivity and specificity.

CONCLUSION

The SUV(max) ratio represents an accurate imaging biomarker for differentiating tonsillar SCC from physiologic (18)F-FDG uptake.