Correlation between radiographic and pathologic lymph node involvement and extranodal extension via CT and PET in...

Extranodal extension (ENE) and more than 4 pathologically involved lymph nodes (pN2) are critical prognostic factors in HPV-associated oropharyngeal cancer (HPV(+) OPSCC). We analyze a patient cohort with HPV(+) OPSCC to determine the sensitivity and specificity of CT and PET/CT in identifying involvement of more than 4 lymph nodes (rN2) compared to pN2 and radiographic ENE (rENE) compared to pathologic ENE (pENE).

The dataset consisted of 261 patients enrolled in two prospective clinical trials. All imaging studies were independently reviewed by a blinded neuroradiologist, classifying the presence or absence of rENE and rN2. Secondary analyses included correlations of imaging accuracy and pathologic size of the primary tumor.

CT demonstrated sensitivity of 59%, specificity of 92%, positive predictive value (PPV) of 53%, negative predictive value (NPV) of 94%, and accuracy of 88% for pN2. PET/CT showed similar results. Patients with up to 4 involved lymph nodes (rN0-1) had a 93-94% chance of remaining pN0-1. CT and PET/CT identified an equal number of involved nodes in 81% of patients. CT demonstrated sensitivity of 54%, specificity of 71%, PPV of 72%, NPV of 53%, and accuracy of 62% for pENE. PET/CT showed similar outcomes. Notably, when multiple radiographic criteria were used to identify rENE, PPV increased for both CT (84%) and PET/CT (79%).

Patients with rN0-1 had a 93-94% chance of remaining pN0-1, suggesting rN0-1 could effectively stratify patients for clinical trials and treatment de-escalation. While CT and PET/CT were highly correlated, both showed low sensitivity for identifying pENE.