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Abstract Introduction Detecting circulating tumor DNA (ctDNA) in the blood using minimally invasive techniques known as a "liquid biopsy", is gaining tremendous popularity in oncology research. Integration of human papillomavirus (HPV) DNA and the overexpression of the E6 and E7 oncogenes are crucial steps in the development of cervical cancer. We investigated the potential utility of HPV ctDNA as a biomarker for monitoring treatment outcomes in patients with cervical cancer. Material and Methods We use droplet digital PCR (ddPCR) to measure the amount of HPV16/18 ctDNA in plasma of cervical cancer patients. The HPV standard GP5+/6+ primers were used to determine HPV positivity in our patients. Specific primers were designed to amplify specifically the E6 oncogene of HPV16 and HPV18. Plasmid constructs were made using the PCR-purified products of HeLa and SiHa cell lines which would act as a positive control for the assay. HPV16 and 18 plasmids were serially diluted and then tested in qPCR as a template using different primer sets. Standard curves were made from the recombinant plasmids. This will serve as a positive control and will also provide a correlation between the sensitivity and specificity of qPCR vs ddPCR. Results and Discussions We hypothesize that our dPCR test will be able to detect minute quantities of HPV ctDNA in plasma of cervical cancer patients as ctDNA levels are expected to be decrease as treatment progresses. The assay sensitivity and specificity will be obtained by comparing results to QPCR. The study samples involve a tumor biopsy and a blood sample at the baseline prior to the therapy and serial blood sampling in different stages of treatment and follow-ups. These samples will also serve for treatment monitoring of these patients through ddPCR. Tumor samples are used to confirm the HPV status of patients using HPV-specific GP5+/GP6+ qPCR. We have recruited 75 cervical cancer patients with majority of them being squamous cell carcinoma and stage IIB disease. The qPCR results from tumor biopsy revealed HPV 16 was most prevalent (32/43), followed by HPV18 (6/43) and HPV 33 (2/43). Conclusion we will now use Qiagen digital PCR system to understand HPV ctDNA levels in our patient cohort. we believe that our comprehensive sample collection after every treatment milestone and thorough follow-up for upto 2 years after diagnosis will allow us to study the utility of this sensitive test in monitoring disease and relapse. Citation Format: Preetiparna Parida, Krishna Sharan, Shirley Lewis, Rama Rao Damerla. Longitudinal monitoring of HPV circulating tumor DNA in cervical cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 2297.
Parida et al. (Fri,) studied this question.