Role of dynamic ctDNA monitoring in cervical and anal epidermoid carcinomas under curative chemoradiation.
Authors: Venchiarutti Moniz Camila M , Bonadio Renata Colombo , Chen Andre Tsin Chih , Ribeiro e Ribeiro Renan , Siqueira Mariana , Braghiroli Maria Ignez , Crosara Marcela , Ortega Cinthia , Nahas Caio , Ibrahim Karim , Rocha Lucila , Dornellas Abraão , Miranda Vanessa Costa , de Mello Evandro Sobroza , Nebuloni Daniela Ribeiro , Genta Maria , Batista Mariana de Paiva , Sabbaga Jorge , Estevez-Diz Maria Del Pilar , Hoff Paulo Marcelo 
Published: June 2024

3141 Background: Cervical and anal canal squamous cell carcinoma (SSC) are a significant health problem in underdevelopment countries. Definitive chemoradiation (CRT) is the standard-of-care (SOC) approach for curative treatment in locally advanced disease. Due to the common substantial local inflammation during CRT, the conventional clinical image cannot identify non-responders early. In this scenario, the evaluation of circulating tumor DNA (ctDNA) is a promising tool for real-time tumor response monitoring. Methods: We performed a prospective multicentric cohort study of patients treated between 2020 and 2023 in tertiary oncologic centers in Brazil to evaluate the role of ctDNA dynamic monitoring in epidermoid cervical (CC) and anal cancer (AC) T1-4, N0-1, M0 by AJCC 8th edition and candidates to complete curative CRT. The cDNA was assessed by Signatera test at D1, D29, immediately post-treatment, 8 weeks (w) post-CRT, 24w post-CRT, every 6 months (m) in the first 1-2 years(y), and yearly at 3-5y of follow-up (FUP). The primary endpoint was to estimate the correlation of ctDNA with a tumoral response assessed by conventional routine image and clinical evaluation at 8w. Secondary endpoints included a correlation between ctDNA results at different time points with progression-free survival (PFS) and overall survival (OS). The predictive potential of the biomarker was evaluated using receiving operating characteristic (ROC) curve analysis. Results: We included 33 patients, and 27 were evaluable with ctDNA, with a median FUP of 10m. The majority were female (n=23, 85.1%), and 3 (11%) were HIV-positive(+). Most patients presented with positive nodes and stage III disease (n=18, 66.6%). In the AC group (n=15), the majority received CRT with capecitabine and cisplatin (n=12, 55.5%); in the CC group (n=12), all pts received cisplatin. All pts tested expressed ctDNA+ before treatment. At 8w, images had a sensitivity of 42.8% and specificity of 100% for disease progression (area under the curve [AUC] 0.714), while ctDNA yielded a sensitivity of 85.7% and specificity of 89.4% (AUC 0.875). The ctDNA+ immediately after CRT ended (32%) was consistent with ctDNA+ at 8w (30.7%) and 24w (30%). Pts with ctDNA+ immediately post CRT have a higher risk of disease progression with PFS of 8.2m in ctDNA+ and not reached in ctDNA- group (HR:17.5; IC95%:1.9-157.3; p=0.01). Data are immature for OS analysis. Conclusions: CtDNA immediately post-CRT has a high predictive value in patients with anal and cervical tumors in early access CRT non-responders, who are at a high risk of disease progression. This biomarker should be considered for tailoring strategies of treatment escalation in this population.