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

Abstract

Objectives: Due to relatively high 18F-fluorodeoxyglucose accumulation in the tonsillar region, the detection of occult tonsillar cancers by 18F-fluorodeoxyglucose positron emission tomography/computerised tomography remains controversial. Therefore, we assessed the usefulness of quantitative tonsil 18F-fluorodeoxyglucose uptake in identifying occult tonsillar squamous cell carcinoma. Design: A case-control study of retrospective cohorts. Setting: University Teaching Hospital. Main outcome measures: We assessed all patients diagnosed with tonsillar cancers or cervical lymph node metastasis of unknown primary tumours between 2005 and 2010 who underwent 18F-fluorodeoxyglucose positron emission tomography/computerised tomography. The subjects were grouped into A (apparent early pT-stage tonsillar squamous cell carcinoma; n = 27), B (occult tonsillar squamous cell carcinoma, primary tumours were found by surgery; n = 21), C (cervical metastasis of unknown primary tumour, primary tumours were not found by surgery and for follow-up; n = 16) and D (33 healthy controls). Tonsillar maximum standardised uptake values were bilaterally measured and compared between groups. Results: The sensitivity and specificity of qualitative assessment of 18F-fluorodeoxyglucose positron emission tomography/computerised tomography for detection of occult tonsillar cancers were 67% and 69%, respectively. Mean maximum standardised uptake values of tonsils with cancer were 11.19 ± 5.46 in group A and 8.12 ± 4.52 in group B, which were significantly higher than that of group C (4.62 ± 1.76) or group D (4.57 ± 1.62) (P < 0.01). The mean maximum standardised uptake value differences of groups A (6.35) and B (3.11) were significantly greater than those of groups C (0.32) and D (0.59) (P < 0.01). Similarly, the mean maximum standardised uptake value ratios of groups A (2.47) and B (1.73) were significantly greater than those of groups C (1.06) and D (1.16) (P < 0.01). Conclusion: 18F-fluorodeoxyglucose positron emission tomography/computerised tomography with tonsil SUVmax measurement is useful to identify occult tonsillar squamous cell carcinoma. ？ 2013 Blackwell Publishing Ltd.