S3 EUS-Guided Fine-Needle Aspiration (FNA) vs Core-Needle Biopsy (CNB) for Diagnostic Yield and Tissue Sampling Adequacy for Molecular Testing in Pancreatic Ductal Adenocarcinoma

Introduction: Pancreatic ductal adenocarcinoma (PDAC) is the third most common cause of cancer death in the US, with a 5-year survival rate of around 9%. Endoscopic ultrasound (EUS) has become the mainstay of diagnosis of pancreatic cancer, with tissue acquisition either through fine-needle aspiration (FNA) or core-needle biopsy (CNB). There is limited literature on the adequacy of samples for molecular testing obtained via FNA versus CNB. Our study aims at comparing these two modalities, regarding sample adequacy for genomic sequencing. Methods: A retrospective chart review was conducted among all patients who underwent EUS, at Saint Luke's Hospital (SLH), KC, MO starting January 1, 2018, till December 31, 2021, for PDAC. Patients were stratified based on the mode of tissue acquisition (FNA vs CNB). Age, gender, tumor size and location, needle gauge size, number of passes, CA 19-9 level, and CEA level, were recorded. Rapid on-site evaluation was performed in all cases by cytotechnologists. Slides review of FNA and FNBs was performed by board-certified cytopathologists for the final pathological diagnosis, tumor surface area, tumor cellularity, and specimen adequacy for molecular testing. Results: A total of 132 patients underwent EUS guided biopsies. 76 of them were FNA, 48 CNB, and 8 were combined. 94.6% (125/132) of the lesions were greater than 2 cm2 in size. 56.8% (75/132) of them involved the head of the pancreas. The mean number of passes needed for CNB and FNA were 2.58 ± 1.06 and 2.49 ± 1.07 respectively. 71.4% (35) of CNB obtained samples were adequate for molecular testing compared to 32.1% (26) of FNA. Genomic testing was performed in 46.4% (26) of CNB samples and in only 23.8% (20) of FNA samples. Conclusion: Although there was no significant difference in the number of passes needed to establish a diagnosis. EUS-CNB under the guidance of rapid on-site specimen evaluation demonstrated a higher value in obtaining adequate samples for molecular testing. Tumor surface area and tumor cellularity play a key role, regardless of tissue acquisition modality. Table 1. - EUS Guided Fine-Needle Aspiration (FNA) Vs Core-Needle Biopsy (CNB) for Diagnostic Yield and Tissue Sampling Adequacy for Molecular Testing in Pancreatic Ductal Adenocarcinoma Baseline patient and procedure characteristics Characteristic CNB (n=48) FNA (n=76) FNA & CNB (n=8) Mean age, years (±SD) 69.88 ± 10.38 72.11 ± 10.86 67.25 ± 9.44 Male, n (%) 22 (45.8%) 36 (47.4%) 6 (75.0%) CEA level, nMedian (Q1, Q3) 155.40 (2.70, 47.90) 275.10 (1.70, 16.90) 28.70 (6.60, 10.80) CA 19-9 level, nMedian (Q1, Q3) 35952.00 (129.00, 4483.00) 53312.00 (43.00, 1661.00) 5195.00 (174.00, 223.00) Complications, n (%) 0 0 0 Characteristic CNB (n=56) FNA (n=84) P value Pancreatic lesion size in cm2< 2 cm2≥ 2 cm2 4 (7.1%)52 (92.9%) 4 (4.8%)80 (95.2%) 0.713 Pancreatic lesion location, n (%)BodyBody and tailHead / uncinate processHead and neckNeck and bodyNeck/genuTail 7 (12.5%)7 (12.5%)28 (50.0%)5 (8.9%)1 (1.8%)2 (3.6%)6 (10.7%) 11 (13.1%)5 (6.0%)50 (59.5%)4 (4.8%)3 (3.6%)2 (2.4%)9 (10.7%) 0.719 Needle gauge, n (%)*20 G22 G25 G 22 (40.0%)32 (58.2%)1 (1.8%) 10 (11.9%)69 (82.1%)5 (6.0%) < 0.001 Categorical variables were compared using chi-square or Fisher's exact test. * There is 1 missing in the CNB group Comparison of pathological characteristics Characteristic CNB (n=56) FNA (n=84) P value Tumor Surface Area in mm2, nMedian (Q1, Q3) 4925.00 (4.00, 100.00) 814.00 (1.00, 25.00) < 0.001 Tumor cellularity*< 20%20%-49%>49% 9 (18.4%)25 (51.0%)15 (30.6%) 30 (37.0%)32 (39.5%)19 (23.5%) 0.079 Mean number of smear slides (±SD) 4.30 ± 2.82 4.49 ± 2.80 0.704 Continuous variables compared using Student's T-test or Wilcoxon rank-sum test. Categorical variables compared using chi-square or Fisher's exact test. * There are 7 missing in CNB group and 3 missing in FNA group. Comparison of outcomes for FNA and CNB Outcome measure CNB (n=56) FNA (n=84) P value Mean pass counts (±SD)* 2.58 ± 1.06 2.49 ± 1.07 0.5096 Sample adequacy for molecular testing, n (%) 35 (71.4%) 26 (32.1%) < 0.001 Genomic testing Performed, n (%) 26 (46.4%) 20 (23.8%) 0.0050 Continuous variables were compared using Student's T-test. Categorical variables were compared using chi-square or Fisher's exact test.*Outcomes were statistically analyzed after adjusting for age, sex, Pancreatic lesion location, and Pancreatic lesion size. There are 3 missing in the CNB group.