(0743) The Role of PET-CT in the Evaluation and Follow-Up of Oral Cavity Squamous Cell Carcinoma

Introduction: PET-CT imaging in oral cavity squamous cell carcinoma (OCSCC) has been steadily increasing. No guidelines specify the proper use of PET-CT and there is some controversy regarding several of its applications; Of these are the utility of PET-CT for detection of occult metastasis and the optimal intervals for PET-CT during FU.
In our practice, PET-CT is performed for staging all new OCSCC except for very early disease. During FU a first scan is performed 3 months after the end of definitive treatment and a second scan 6 months following the first scan.
Our aim is to examine the efficacy of PET-CT in diagnosing occult spread to lymph nodes in OCSSC and assess the most beneficial time-frame during post-treatment FU to perform PET-CT.

Methods: Retrospective review of electronic medical records of OCSCC patients who were operated between 2018-2023. Demographic and clinical data was recorded and imaging studies were analyzed.

Results: A total of 138 patients were included. Over half of the patients (69.5%) were diagnosed with an advanced stage 3-4 disease.
Forty-eight (43%) patients had pathological lymph node involvement; All of them with T2-T4 tumor. Fifteen patients (31%) had clinically negative neck prior to surgery of whom a third had a PET-CT scan showing lymph node involvement.
Thirty-two (23%) patients suffered from recurrence within a median time of 7 months following surgery. 85% of the recurrences occurred withing the first year after treatment. Most recurrences were distant metastases (34.4%) and spread to regional lymph nodes (31.3%). Whereas physical examination identified all local recurrences it was able to detect only 10% of either regional and distant metastasis. PET-CT diagnosed 90% of regional spread and all cases of metastatic disease.

Conclusions: PET-CT is a valuable tool during pre-operative staging as it may detect clinically occult neck involvement in a third of the patients. Its use during FU is imperative not only for detection of distant metastasis but also for regional metastasis which are often missed by physical examination. Our time-frame for performing PET-CT covers the vast majority of recurrences.