Abstract PO-044: Correlation between circulating tumor DNA and tumor volume in head and neck cancer
Authors: Okifo Oghenefejiro , Wu Vivian , Tam Samantha , Khatib Sondos Al , Siddiqui Farzan 
Published: September 2023

Abstract
Purpose: NavDx is a DNA test that has been used widely in head and neck cancer to quantify fragments of circulating tumor tissue modified viral DNA (TTMV HPV DNA), an HPV-specific cancer biomarker that is shed into the blood. Circulating tumor DNA has shown promise in monitoring tumor progression and therapeutic efficacy and therefore has potential to assist in improved cancer diagnosis and treatment. Recent studies have demonstrated a correlation between circulating tumor DNA and tumor volume in metastatic pancreatic ductal adenocarcinoma and metastatic breast cancer. The purpose of the study is to determine whether there is a correlation between positive vs. negative circulating tumor DNA at baseline as well as the quantity of circulating fragments and tumor volume in head and neck cancer patients. Methods: In this retrospective cohort study, data was extracted from our NavDx database (Naveris Systems) for 39 patients with p16 positive head and neck cancer with subsites in the base of tongue and tonsil. Logistic regression analyses were performed to compare tumor volume and tumor site in all patients and then by the subsites of base of tongue and tonsil. To address multicollinearity, different models were created for primary tumor volume, nodal volume, and total tumor volumes. Contrast enhanced diagnostic or radiation treatment planning CT scans were imported into Varian Aria (Varian Medical Systems, Palo Alto, CA). The primary and nodal disease was delineated to determine the total and sub-volumes. The relationship was examined between the tumor volumes and positive vs. negative/indeterminate circulating tumor DNA. Linear regression analysis was also performed to assess the relationship between tumor volumes and circulating fragments of TTMV-HPV 16. Results: A total of 39 patients were included in the study, including 36 males and 3 females, ages ranging from 42 to 79, and patients staged from Stage I to Stage IVA. 13 patients underwent surgical intervention. Subsites included the tonsil for 21 patients and base of tongue for 19 patients that were included in the analysis. There was a positive correlation between nodal volume and circulating TTMV-HPV16 fragments (p= 0.024) in all patients. There was a difference in tumor volume with an odds ratio of 1.41 and nodal volume with an odds ratio of 1.04 compared with positive vs. negative circulating DNA in all patients (p = 0.374; p = 0.906). Conclusions: The data demonstrated a positive correlation between nodal volume and circulating TTMV-HPV 16 fragments (p = 0.024). There was a difference in tumor and nodal tumor volumes with positive vs. negative circulating tumor DNA in all patients, however this did not reach statistical significance. While there was an association with nodal volume, further investigation is needed to determine why patients with p16 positive head and neck cancer may have negative serum circulating tumor DNA. Additional studies with a larger sample size can also better elucidate the relationship between circulating tumor DNA and tumor burden in H&N patients.
Citation Format: Oghenefejiro Okifo, Vivian Wu, Samantha Tam, Sondos Al Khatib, Farzan Siddiqui. Correlation between circulating tumor DNA and tumor volume in head and neck cancer [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Innovating through Basic, Clinical, and Translational Research; 2023 Jul 7-8; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2023;29(18_Suppl):Abstract nr PO-044.