Incidental Diagnosis of Pancreatic Cancer and Association with Improved Patient Outcomes: Assessing the Potential Clinical Utility of Liquid Biopsy Based Screening Tests

Background: Poor outcomes in pancreatic ductal adenocarcinoma (PDAC) are associated with delayed diagnosis and early systemic spread of disease. Development of liquid biopsies for screening could help detect low-stage disease in asymptomatic patients. We aimed to evaluate the association between incidental diagnosis on outcomes and assess the potential role of liquid biopsies. Study Design: An institutional registry was used to identify patients undergoing resection for PDAC at between 2010 and 2015. Patients were stratified based on presenting symptoms, and outcomes were analyzed. Preoperatively collected plasma that was available on these patients was analyzed using a multianalyte screening test based on ctDNA and proteins. Results: Seventy-nine (9.6%) of 823 patients were diagnosed incidentally (asymptomatic at diagnosis). Incidental diagnosis was associated with type of surgery, and absence of nodal disease and lymphovascular invasion (all P<0.05). On multivariable analysis incidental diagnosis (HR, 0.561; 95%CI, 0.406-0.775; P<0.001) was independently associated with improved overall survival (OS), while tumor size ≥4cm (HR, 1.617; 95%CI, 1.201-2.176; P=0.002), nodal disease (HR, 1.259; 95%CI, 1.018-1.558; P=0.034), perineural invasion (HR,1.338; 95%CI, 1.030-1.739; P=0.029), and positive margins (HR,1.302; 95%CI, 1.058-1.602; P=0.013) were associated with poorer OS. Asymptomatic patients had a significantly longer OS (median-OS: 38 vs. 19 months (P<0.001). The rate of multianalyte test positivity was 75% (6/8) in asymptomatic patients compared to 73% (59/81) in symptomatic patients (P=0.895). Conclusion: Approximately 10% of patients with PDAC are diagnosed incidentally. In resected PDAC, incidental diagnosis is independently associated with improved OS. Multianalyte screening tests perform equally well in asymptomatic and symptomatic patients. These findings further reinforce the need for development of screening tools that can increase the rate of diagnosis at an asymptomatic stage and improve survival.