Preoperative MRI and 18F-FDG PET/CT for cervical lymph node metastasis in oral squamous cell carcinoma: a retrospective study of diagnostic performance and pathological nodal metastasis among imaging-negative patients

Accurate preoperative detection of cervical lymph node metastasis is important in oral squamous cell carcinoma (OSCC). This study aimed to compare the diagnostic performance of magnetic resonance imaging (MRI) and 18 F-fluorodeoxyglucose ( 18 F-FDG) positron emission tomography/computed tomography (PET/CT) for detecting cervical lymph node metastasis in patients with OSCC, analyze the factors associated with diagnostic performance and evaluate pathological nodal metastasis among imaging-negative patients. This single-center retrospective study included 211 patients with OSCC who underwent preoperative MRI, 18 F-FDG PET/CT and neck dissection, and 856 cervical lymph node levels were analyzed. Diagnostic performance was compared. Generalized estimating equation (GEE) models were used for level-based univariable and multivariable subgroup analyses. Logistic regression was used to analyze factors associated with pathological nodal metastasis in each imaging-negative group. At the patient level, MRI showed numerically higher sensitivity than PET/CT (71.4% and 67.1%, respectively); however, the difference was not statistically significant ( p = 0.453). PET/CT showed significantly greater specificity than MRI (85.8% and 69.5%, respectively; p < 0.001). In level-based multivariable GEE analysis, clinical T3–4 category was independently associated with higher sensitivity for both modalities, whereas greater daily cigarette consumption and Levels III–V were independently associated with lower sensitivity. Levels III–V were also independently associated with higher specificity for both imaging modalities. Additionally, primary tumors not involving the tongue or floor of the mouth were independently associated with lower MRI specificity. Pathological nodal metastasis occurred in 16.9% and 16.0% of MRI- and PET/CT-negative patients, respectively. Patient-level multivariable logistic regression analysis showed that greater daily cigarette consumption was associated with pathological nodal metastasis in both imaging-negative groups. At the patient level, MRI showed numerically higher sensitivity than PET/CT, but the difference was not statistically significant, whereas PET/CT showed significantly higher specificity. Negative MRI or PET/CT findings did not completely exclude pathological nodal metastasis. Clinical T category, cervical lymph node level category, daily cigarette consumption and primary tumor site were associated with diagnostic performance. Furthermore, daily cigarette consumption was associated with pathological nodal metastasis among patients in both the MRI-negative and PET/CT-negative groups.