111PCombined genomic and epigenomic assessment of cell-free circulating tumour DNA (cfDNA) for cancer diagnosis and recurrence-risk assessment in early-stage lung cancer

Abstract Background Circulating tumor DNA (ctDNA) analysis has been successfully applied to therapy selection and treatment monitoring in advanced cancer patients. However, it is not yet established whether ctDNA can be used clinically for early cancer detection or recurrence prediction in early stage lung cancer patients. Methods We analyzed pre-operative plasma samples from 55 early stage NSCLC patients (stages I-IIIA) using next-generation sequencing assay incorporating somatic and epigenomic analysis, and a bioinformatic classifier to filter non-tumor derived variants. Table: 111P . Cell type Stage Somatic mutation Epigenetic pattern Total number Recurrence+, n (%) Site of recurrence Adenocarcinoma stage 1 ctDNA- methylation- 9 1 (11) Lung n = 17 methylation+ 6 2 (33.3) Stump, bone ctDNA+ 2 1 (50) lung stage 2 ctDNA- methylation- 0 0 (0) n = 2 methylation+ 0 0(0) ctDNA+ 1 1 (100) multiple stage 3 ctDNA- methylation- 0 0 (0) n = 4 methylation+ 2 0 (0) ctDNA+ 2 2 (100) brain, multiple Sqaumous cell carcinoma stage1 ctDNA- methylation- 0 0 (0) n = 7 methylation+ 3 0 (0) ctDNA+ 4 1 (25) multiple stage2 ctDNA- methylation- 0 0 (0) n = 9 methylation+ 0 0 (0) ctDNA+ 9 2 (22.2) multiple, lung stage3 ctDNA- methylation- 0 0 (0) n = 4 methylation+ 1 0 (0) ctDNA+ 3 1 (33.3) Mediastinal LNs Results Somatic mutation analysis alone detected ctDNA in 42% (23/55) of patients, whereas combined mutational and epigenomic analysis detected ctDNA in 67% (37/55). ctDNA detection rate varied by pathological subtypes; using combined approach, ctDNA was detected in all squamous cell carcinoma patients, while only 55% (12/22) in adenocarcinoma (ADC) (p=0.006). Within the ADC subgroup, ctDNA detection rates using the combined approach were dependent on disease stage: 47% (8/17) in stage I, 100% (2/2) in stage II, and 100% (2/2) in stage IIIA. Importantly, within 2 years of follow-up, pre-operative ctDNA status was correlated with tumor recurrence after resection; among 17 stage I ADC patients, three of eight (38%) ctDNA-positive cases showed recurrence, while only one of nine (11%) ctDNA-negative cased did (p=0.29). Interestingly, patients with somatic mutation in their ctDNA have shown higher recurrence rate. Conclusion Utilizing a plasma-only sequencing assay incorporating somatic genomic and epigenomic analysis, ctDNA detection rate in early stage lung cancer (stage I-III) can far outperform the detection rate of somatic sequence variant detection alone. And, the presence of pre-operative ctDNA in patients with early stage lung adenocarcinoma may identify those who are more likely to have disease recurrence. Legal entity responsible for the study: Guradant Health, Inc. Funding Guardant Health, Redwood City, CA, USA. Disclosure I. Kim: Full / Part-time employment, Officer / Board of Directors: Guardant Health. M. Shultz: Officer / Board of Directors: Guardant Health. A. Jaimovich: Officer / Board of Directors: Guardant Health. J. Odegaard: Officer / Board of Directors: Guardant health, Inc. S. Olsen: Officer / Board of Directors: Guardant Health, Inc. A. Talasaz: Officer / Board of Directors: Guardant health. J. Kim: Research grant / Funding (self): Guardant health, Inc. All other authors have declared no conflicts of interest.