Abstract 93: Utility of the Cytosponge for Aetiological Research in Esophageal Squamous Cell Carcinoma: Proof-of-Concept Pilot Study Using Tobacco-Specific Methylation Markers

Purpose: Esophageal cancer caused 544,076 deaths in 2020. It has two major subtypes: esophageal adenocarcinoma (EAC) and esophageal squamous cell carcinoma (ESCC). A geographically intriguing African Esophageal Cancer Corridor has very high incidence and mortality rates for ESCC. We propose that ESCC research in this corridor might benefit from leveraging advances in tools used for the early detection of EAC, namely using the esophageal sponge cytology. The Cytosponge™ was developed by the University of Cambridge Fitzgerald-laboratory. This pill-on-a-string is an endoscopy-alternative and may form an attractive appropriate health technology in Africa. However, use of the Cytosponge™ for ESCC research in Africa is limited to the CytoSCCAPE study which demonstrated high acceptability and safety of administering the device among 102 asymptomatic adult community volunteers in Kilimanjaro, Tanzania. Methods: In the present proof-of-concept pilot study, we investigated whether FFPE cytology blocks obtained in the CytoSCCAPE study could be used for exposure-specific methylation studies, via two objectives: (i) examine DNA yield from the cytology blocks and (ii) evaluating if the isolated DNA can be used for investigating DNA methylation-based exposure analysis. Here we performed pyrosequencing to compare DNA methylation status of established tobacco-specific methylation markers (CpG cg05575921 & a nearby CpG locus) in ever compared to never tobacco users. Results: Among 102 participants (mean age 50 (SD 12) years, 52% female), 58% (N=58) had good DNA yield (>100 ng), 19 had poor DNA concentration (range 3-54.9ng) and 25 had low DNA concentration (range 60-104ng). In total, 49 (77%) samples passed the quantification stage out of 64 samples that were pyrosequenced. Among these 49 participants, median (IQR) cg05575921 methylation was low overall: 33% (27-44) and did not differ between the 8 ever and 41 never-tobacco users (p=0.85). Hypomethylation in tobacco consumers was not observed, in contrast to work published using blood DNA. Conclusion: We discuss possible reasons for this inconsistency, which include low cellularity and deparaffinization of FFPE sections and provide recommendations for future Cytosponge™ studies for ESCC etiological research. Citation Format: Hannah Simba, Fazlur Rahman Taludkar, Daniel Middleton, Blandina Mmbaga, Alex Mremi, Valerie McCormack. Utility of the Cytosponge for Aetiological Research in Esophageal Squamous Cell Carcinoma: Proof-of-Concept Pilot Study Using Tobacco-Specific Methylation Markers [abstract]. In: Proceedings of the 11th Annual Symposium on Global Cancer Research; Closing the Research-to-Implementation Gap; 2023 Apr 4-6. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(6_Suppl):Abstract nr 93.