Real-world utility of full staging with 18-fluorodeoxyglucose positron emission tomography (18FDG-PET) in addition to standard imaging in patients with non-metastatic non-resectable pancreatic ductal adenocarcinoma (PDAC)

Abstract

Background: Previous studies support 18FDG-PET utility for staging of patients (pts) with non-metastatic PDAC (M0-PDAC); while its use has been adopted in some countries (i.e. NICE guidelines in the United Kingdom), its use in this setting is vari- able, especially in relation to non-resectable disease. This study explored the utility of performing 18FDG-PET in real-world clinical practice for pts with a working diagnosis of non-resectable M0-PDAC based on cross-sectional imaging. Methods: Notes from consecutive pts with PDAC seen at The Christie NHS Foundation Trust (01/07/2018-02/02/2022; Audit Committee approval: 2020/2654) were reviewed. Eligible pts were those with a diagnosis of non-resectable M0-PDAC (with primary tumour in situ) who underwent full staging with an 18FDG-PET (standard practice for all pts during time period explored). The primary end-point was the percentage of pts identified to have distant metastases on 18FDG-PET. Secondary objectives: factors associated with presence of distant metastases, and impact of 18FDG-PET findings on patient outcomes (overall survival (OS); defined as the time from when pts were first seen for consideration of systemic therapies to time of death or last follow-up). Statistical analysis: STATA v.17, including logistic and Cox Regression. Results: A total of 1637 pts were screened; of these, 56 were eligible. Thirty pts (53.37%) were male; median age: 72 years (range 34-83); the majority had primary tumour located in the head (n¼40, 71.43%), ECOG performance Status (ECOG PS) 0/1 (n¼48, 85.71%) with none/mild comorbidities (37 pts, 66.07%; 22 pts (39.29%) had diabetes) and treatment naive (52 pts, 92.86%; 4 pts had received prior chemo- therapy (all FOLFIRINOX)); stage prior to 18FDG-PET: T4 (39 patients; 69.64%), regional lymph node disease (25 patients; 44.64%), M0 (56 patients; 100%). In 19 patients (33.93%) the 18FDG-PET identified presence of metastatic disease; with incidental findings in 12 patients (21.50%) (incidental findings were identified in 7 patients without evidence of distant metastatic disease in 18FDG-PET). Logistic regression identified T4 stage (vs T1/2/3 stage) as the only factor associate with higher risk of metastatic disease in 18FDG-PET (46.15% vs 5.88%; Odds Ration (OR) 13.71 (95% 1.65-113.81); p-value 0.015). At time of analysis 31 patients (55.36%) had died; median follow up was 8.54 months (95% CI 6.10-10.64). Estimated median OS for the whole population was 12.53 months (95% CI 9.16-14.74). Patients identified to have presence of distant metastases in 18FDG-PET had a shorter OS (8.07 months (95% CI 4.23-16.53) vs 14.38 (95% CI 11.01-19.17)); prognostic impact was confirmed in multivariable Cox Regression (HR 3.48 (95% CI 1.76-12.04); p-value 0.002) adjusted to other prognostic factors (PS (HR 3.48 (95% CI 1.57-7.71); p-value 0.002)). Conclusions: 18FDG-PET allows identification of otherwise occult metastatic disease in a third of the pts (this rate is higher for patients with stage T4 disease). Staging with 18FDG-PET in pts with non-resectable M0-PDAC should be considered standard of care to allow access to appropriate standard-of-care treatment options and recruit- ment into clinical trials. In addition, its prognostic implications could enable optimi- sation of patient information given, management of expectations and future care planning.