18F-fluorodeoxyglucose uptake level-based lymph node staging in oropharyngeal squamous cell cancer--role of molecular marker expression on diagnostic outcome.

BACKGROUND: A prospective study was performed to assess standard uptake value (SUV)-level based (18)F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) lymph node staging in 33 patients with oropharyngeal squamous cell cancer (OSCC) out of a total of 99 patients with head-and-neck squamous cell cancer (HNSCC) and the role of nodal molecular marker expression in diagnostic outcome prediction. METHODS: Preoperative nodal PET/CT staging in 123 lymph nodes was correlated with postoperative lymph node histology, which served as gold standard. Tissue samples were prepared for immunohistochemistry of the excised lymph nodes. RESULTS: The negative and positive predictive values (NPV and PPV) of PET for correct lymph node assessment were 100% and 93%, respectively. There was a significant association between SUVmax and lymph node histology (p < 0.0001) and a significant linear correlation between SUVmax and nodal size (Pearson's correlation coefficient r = 0.61336, p < 0.0001). The molecular marker E-Cadherin was significantly overexpressed in lymph node metastases (p < 0.0001). Benign lymph nodes showed significant 2-fold Bcl2 overexpression (p < 0.0001). However, the molecular marker expression profiles were inhomogeneous and did not allow valuable diagnostic outcome prediction. CONCLUSIONS: SUV level-based (18)F-FDG-PET/CT lymph node assessment in OSCC still has to be considered as the most established and reliable staging tool. Lymph node molecular marker expression profiles need to be investigated further as they currently do not sufficiently contribute to therapy decision-making.

Effect of reconstruction parameters in high-definition PET/CT on assessment of lymph node metastases in head and neck squamous cell carcinoma.

UNLABELLED: Therapy outcome and overall survival in patients with head and neck squamous cell carcinoma (HNSCC) is influenced by precise localization of the primary tumor and detection of lymph node metastasis involvement at the time of initial diagnosis. Only accurate preoperative staging can improve primary tumor response and avoid early locoregional recurrence with lymph node metastases. The purpose of this study was the optimization of reconstruction parameters in high-definition PET/CT for the improved diagnostic assessment of lymph node metastases. METHODS: In the experimental study, image contrast and signal-to-noise ratio were evaluated using a Jaszczak phantom. In the clinical study, 54 patients underwent head and neck imaging on a PET/CT scanner. Diagnostic findings were correlated with postoperative histopathology. For the 54 patients, 123 lymph nodes were evaluated on PET and histologically correlated with the neck dissection specimen. Forty-one lymph nodes were benign, and 82 findings were confirmed as being malignant. Both experimental and clinical studies were reconstructed into a 200 × 200 matrix using a 3-dimensional iterative reconstruction algorithm (ordered-subset expectation maximization [OSEM], 3 iterative steps, 24 subsets). Postfiltering with a 3-dimensional gaussian filter was applied. To study the effect of smoothing filter strength on the diagnostic accuracy of lymph node metastasis detection, 3 different cutoffs-1, 3, and 6 mm in full width at half maximum-were used to perform reconstructions. RESULTS: Phantom studies showed that images reconstructed with 3-mm gaussian postfiltering gained a higher image quality and signal-to-noise ratio. Overall sensitivities for correctly diagnosed lymph nodes were best in 3-mm postfiltered images. Best results for true-positive lymph node findings were achieved with 3-mm postfiltering. With 1-mm postfiltering, accurate lesion detection was not improved, because increasing sensitivity (95% true-positive) correlated with decreasing specificity (12% false-positive). CONCLUSION: For lymph node assessment on a high-resolution PET/CT scanner, we consider the OSEM algorithm with 3 iterations and 24 subsets, combined with 3-dimensional 3-mm gaussian postfiltering, to be optimal. The continuous application of presently established PET protocols in patients with HNSCC will prove whether current acquisition and reconstruction methods are valuable and should be maintained.