Relationship between extracapsular spread and FDG PET/CT in oropharyngeal squamous cell carcinoma

Conclusion: Median maximum standardized uptake (SUVmax) cut-off values of FDG PET/CT higher than 3.85 were found to be associated with a greater risk cervical lymph node metastasis with extracapsular spread (ECS) in patients with oropharyngeal squamous cell carcinoma (OPSCC). Objectives: The purpose of this study was to evaluate the use of FDG PET/CT for the identification of ECS and to establish its histologic correlates in OPSCC. Methods: The medical records of 78 patients who underwent FDG PET/CT for OPSCC before surgery were reviewed. Results: ECS was present in 42% (42/69) of dissected necks and in 51% (54/106) of dissected cervical levels. The SUVmax values of cervical lymph nodes with and without ECS were found to be significantly different (6.73 ± 3.78 vs 3.02 ± 2.24, p < 0.001). The SUVmax cut-off value for differentiating necks with ECS from those without ECS was 3.85. The presence of ECS (p = 0.036) and median SUVmax (using 3.85 as a cut-off) (p = 0.037) were found to have a significant adverse effect on 5-year disease-specific survival by univariate analysis. The multivariate analysis showed a significant association of 5-year disease-specific survival with ECS (hazard ratio (HR) = 32.3 in cervical metastasis with ECS, p = 0.012; and HR = 19.6 in cervical metastasis without ECS, p = 0.024).