Dynamic ctDNA Assessment in Cervical and Anal Canal Tumors: Optimizing Follow-up and Clinical Outcomes

After definitive radiotherapy (RT) treatment (with or without chemotherapy), cervical and anal canal neoplasms frequently exhibit disease persistence or recurrence. Due to the local inflammatory process post-treatment, response assessment by imaging (current gold standard) is limited, often necessitating multiple follow-ups and repeated invasive biopsies. Conventional follow-up is complex and costly, requiring equipment from secondary and tertiary services, trained radiologists, and patient exposure to radiation and contrast. In this context of human papillomavirus(HPV)-related neoplasms, recent studies have demonstrated the role of ctDNA (circulating tumor DNA) in assessing the risk of recurrence or disease progression, providing a rationale for using the tool in two fronts: * Optimizing follow-up based on serial monitoring of ctDNA; * Selecting patients with positive ctDNA after RT, who are at high risk of recurrence, for treatment intensification. Monitoring with ctDNA as a standalone follow-up tool in cases evolving with negative ctDNA after RT has the potential to replace imaging exams, being a minimally invasive test performed on a peripheral blood sample. Currently, ctDNA testing has expensive methodologies not available in the Unified Health System (SUS). This project aims to develop a methodology for ctDNA evaluation focused on HPV ctDNA research that is low-cost and executable in SUS, as well to assess the accuracy of this test in the population with HPV-related tumors. Additionally, we will evaluate whether the early introduction of immunotherapy in patients with positive ctDNA after definitive treatment can increase cure rates. Immunotherapy already has a well-defined role in the treatment of metastatic HPV-related neoplasms. Recently, the use of anti-programmed death-1 (anti-PD1) has also shown benefits in patients with locally advanced cervical cancer with a high risk of recurrence who are candidates for chemoradiotherapy (CRT). Therefore, its use focused on HPV-related tumors, as well as a better understanding of which patients benefit from this strategy, warrants further investigation.