Rapid Fire Best of the Best Poster Oral Clinical Oncology Society of Australia Annual Scientific Meeting 2022

Relationship between circulating tumour DNA and skeletal muscle stores at diagnosis of pancreatic ductal adenocarcinoma (#122)

Lauren Hanna 1 2 , Rav Sellahewa 3 4 , Catherine E Huggins 2 5 , Joanne Lundy 3 4 , Daniel Croagh 3 6
  1. Department of Nutrition and Dietetics, Monash Health, Clayton, VIC , Australia
  2. Department of Nutrition, Dietetics and Food, Monash University, Notting Hill, VIC, Australia
  3. Department of Surgery, Monash University, Clayton, VIC, Australia
  4. Department of Molecular and Translational Science, Monash University, Clayton, VIC, Australia
  5. Globe Obesity Centre (GLOBE), Institute for Health Transformation, Deakin University, Burwood, VIC, Australia
  6. Department of Upper Gastrointestinal Surgery, Monash Health, Clayton, VIC, Australia

Background: Low skeletal muscle index (SMI) and skeletal muscle radiodensity (SMD) are associated with reduced survival time in pancreatic ductal adenocarcinoma (PDAC). The negative prognostic impact of low SMI and low SMD is often reported as independent of cancer stage when using traditional clinical staging tools. Therefore, this study sought to explore the relationship between a novel marker of tumour burden (circulating tumour DNA) and skeletal muscle abnormalities at diagnosis of PDAC

Methods: A retrospective cross-sectional study was conducted in patients who had plasma and tumour tissue samples stored in the Victorian Pancreatic Cancer Biobank (VPCB) at diagnosis of PDAC, between 2015 and 2020. Circulating tumour DNA (ctDNA) of patients with G12 and G13 KRAS mutations was detected and quantified. Pre-treatment SMI and SMD derived from analysis of diagnostic computed tomography (CT) imaging was tested for its association to presence and concentration of ctDNA, as well as conventional staging, and demographic variables.

Results: The study included 66 patients at PDAC diagnosis; 53% female, mean age 68.7 (SD±10.9) years. Low SMI and low SMD were present in 69.7% and 62.1% of patients, respectively. Female gender was an independent risk factor for low SMI (OR 4.38, 95% CI 1.23-15.55, p=0.022), and older age an independent risk factor for low SMD (OR 1.066, 95% CI 1.002-1.135, p=0.044). No association between CT-derived skeletal muscle stores and ctDNA or conventional staging was observed.

Conclusion: At PDAC diagnosis, skeletal muscle abnormalities are a comorbidity of cancer and not related to tumour burden. Future studies are needed to identify the mechanisms and risk factors for low SMI and low SMD at diagnosis of PDAC to aid intervention development and screening.