Role of FDG-PET/CT in Determining DOI and PNI in OSCC-A Retrospective Study from Eastern India

Oral squamous cell carcinoma is the most common malignancy in the head and neck region. The DOI and PNI are important prognostic factors. DOI greater than 4 mm is also used as an indication for elective neck node dissection. FDG-PET/CT is now used in head and neck cancers for the delineation of the primary tumor, detection of regional nodal metastases, distant metastases, and second primary tumors. In our study, we have tried to show the correlation between preoperative FDG uptake values and postoperative histopathological parameters such as DOI and PNI. Two hundred eighty-four patients with OSCC who presented to us underwent whole-body FDG-PET/CT in addition to the routine evaluation. The patients underwent surgeries for the primary lesion and neck dissection. DOI data was segregated into ≤ 4 mm and > 4 mm. PNI was segregated into positive and negative. ROC was plotted to know the cutoff point of SUVmax in predicting DOI and PNI. For predicting the DOI > 4 mm, the cutoff point for SUVmax was 8.88 with a specificity of 76.4 and sensitivity of 69.8 (Youden's index - .660), area under the curve 0.771, and p value of 0.001. For predicting the presence of PNI, the cutoff point for SUVmax was 13.33 with sensitivity of 49.4 and specificity of 70.8. Preoperative FDG PET/CT can predict the depth of invasion in lesions that appear to be less than 4 mm clinically and help in decisions regarding elective neck dissections. Although the sensitivity and specificity of FDG PET/CT in predicting PNI are low but SUVmax above 13.33 can be considered a poor prognostic factor, considering the possibility of PNI positivity. FDG-PET/CT should not only be used for the diagnosis of distant metastases and identification of second primary. It can also be used for the identification of poor prognostic factors such as DOI and PNI.