S29 Dilated Main Pancreatic Duct Without a Visible Pancreatic Mass: Long-Term Follow-Up and Predictors of Future Pancreatic Ductal Adenocarcinoma

Abstract

Introduction: Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease frequently diagnosed at an advanced stage when therapeutic options are limited. Pancreatic imaging abnormalities that predate diagnosis of PDAC may serve as an early detection tool. Dilation of the main pancreatic duct (D-MPD) has been shown to occur up to a year before PDAC diagnosis. However, while D-MPD in the absence of a visible pancreatic mass raises concern for occult neoplasm, the natural history of D-MPD remains poorly understood. From a large cohort of patients with D-MPD and no pancreatic mass, we aimed to assess long-term outcomes and compare patients who were subsequently diagnosed with PDAC to those who did not develop PDAC. Methods: We identified all subjects ≥18 years old at our institution with D-MPD (MPD >3mm) on either abdomen/pelvis CT or MRI scans between 1/1/2012 and 12/31/2017. Patients with prior PDAC, pancreatic surgery, definite pancreas mass or other visible cause of D-MPD were excluded after expert review by study radiologist. Pertinent clinical, demographic, and imaging data were summarized. A stratified univariate Cox proportional hazards model was utilized to evaluate risk factors for PDAC development. Results: Among 2307 patients (baseline CT:1615, MRI: 692) who met our study criteria, 63.7% were female, median age was 71 (IQR 59.5 -80.1), and median follow-up was 1466 days (IQR 1426-1509). The 1-year and 3-year event rates for PDAC were 2.70 and 2.99 per 100-patient years respectively. Out of sixty-three (2.7%) patients who developed PDAC within 3 years of the baseline scan, the majority (58/63) were within 1 year (Figure). Factors associated with a significantly increased 3-year risk of PDAC included male gender, BMI >25, diabetes mellitus, non-O blood type, elevated serum CA 19-9, focal narrowing of MPD, equivocal pancreatic mass and suboptimal baseline scan quality (Table). Conclusion: D-MPD may predate the diagnosis PDAC and raises concern for neoplasm. However, in our study only a small subset of D-MPD patients without an overt pancreatic mass developed PDAC on follow-up. The risk is highest in the first year with rare events after one year of PDAC-free follow-up. Risk factors identified in this study may enrich assessment and guide surveillance of patients with D-MPD. Future studies exploring machine learning tools can further enhance the identification of those at risk of future PDAC and facilitate early detection.Figure 1.: Kaplan-Meier curve estimate of PDAC event rates over the 3-year followup duration Table 1. - Univariate Survival Analysis (w/ strata) assessing the risk of developing PDAC within 3 years from baseline CT/MRI in 2307 patients with D-MPD Characteristics Reference Hazard Ratio 95% HR CI p-value Age (years) ≥50 < 50 7.109 0.987 51.192 0.0515 Body Mass Index (kg/m2) ≥25 < 25 1.972 1.172 3.319 0.0105 Maximum MPD diameter (mm) ≥5-< 10 ≥3-< 5 3.773 1.987 7.167 < .0001 ≥10 ≥3-< 5 20.081 8.455 47.691 < .0001 CA19-9 ≥35 < 35 4.819 2.678 8.670 < .0001 Gender Male Female 1.937 1.181 3.176 0.0088 ABO Blood type Type Non- O Type O 2.238 1.162 4.310 0.0161 Alcohol Ever Use Never Use 1.029 0.612 1.731 0.9137 Aspirin Ever Use Never Use 0.936 0.534 1.640 0.8177 Diabetes mellitus Yes No 2.596 1.554 4.338 0.0003 Chronic Pancreatitis Yes No 0.386 0.094 1.576 0.1847 Acute Pancreatitis Yes No 1.116 0.551 2.260 0.7609 Family History of PDAC Yes No 1.952 0.930 4.097 0.0772 Pancreas Cyst on imaging Yes No 1.444 0.856 2.439 0.1688 Equivocal Mass on imaging Yes No 12.524 7.248 21.640 < .0001 Image Quality Suboptimal but diagnostic Optimal 2.241 1.309 3.839 0.0033 Dilation Pattern Segmental/Multifocal Diffuse 1.175 0.717 1.926 0.5214 Focal Narrowing of the MPD Present Absent 40.800 9.732 171.038 < .0001