High diagnostic accuracy for lymph node metastasis of oral squamous cell carcinoma using PET/CT with a silicon photomultiplier.

Objective: The higher sensitivity of the new-generation positron emission tomography/computed tomography (PET/CT) with silicon photomultiplier (SiPM) may increase false-positive rates in detecting metastatic lymph nodes (LNs). This study aimed to clarify the usefulness of the SiPM PET scanner in diagnosing LN metastasis of oral squamous cell carcinoma (SCC).

Methods: We retrospectively reviewed consecutive F-18 fluorodeoxyglucose PET/CT images of 39 SCC patients using SiPM PET and 31 SCC patients using non-SiPM PET. We measured the maximum standardized uptake value (SUV) of the LNs on PET images and maximum short-axis diameter on transverse CT images.

Results: The sensitivity and specificity of SiPM PET were 86.2% and 95.6%, respectively (cut-off SUV, 4.6). The area under the curve (AUC) of SiPM PET (0.977; 95% confidence interval [CI], 0.958-0.995) was significantly higher than that of non-SiPM PET (0.825; 95% CI 0.717-0.934) (P < 0.01). In a size-limited analysis of diameter, the AUC of SiPM PET (≥ 0.96 for all diameters) was significantly higher than that of non-SiPM PET (tended to decrease as the LN diameter decreased) for the diagnosis of LN metastasis by SUV.

Conclusion: SiPM PET had higher diagnostic accuracy for LN metastasis of oral SCC than non-SiPM PET, even for small LN metastasis without increasing false-positives.