USEFULNESS OF EUS-GUIDED FINE NEEDLE BIOPSY FOR SMALL PANCREATIC NEUROENDOCRINE NEOPLASM: KOREAN MULTICENTER NATIONWIDE STUDY

Aims Pancreatic neuroendocrine neoplasm (PNEN) represents heterogeneous biological behavior, and most of small PNENs 2 cm or less in size are known to show indolent feature. Thus, observation can be considered in selected cases according to the NCCN guideline, however, there is a lack of clinical evidence, and the criteria are vague. We evaluated the usefulness of EUS-guided fine needle biopsy in determination of treatment plan for small PNEN.

Methods A total of 158 patients from 14 institutions with pathologically confirmed PNENs 2 cm or less in initial imaging were enrolled. The primary outcome was any event of metastasis or recurrence during follow up.

Results The median age was 57.5 years (range, 22-84 years), and 86 patients (54%) were female. Eighteen patients (11%) had a tumor-related symptoms at initial diagnosis, and the median size of the tumor was 1.3 cm (range, 0.7-2.0 cm). The results of WHO classification were available in 147 patients: 126 patients (86%) with grade 1 and 21 patients (14%) with grade 2. Pathological diagnosis with EUS-guided aspiration biopsy was confirmed in 22 patients, and among them, identification of WHO classification was also available in 17 patients. Among six patients who underwent EUS-guided aspiration biopsy and surgery together, the concordance rate of WHO classification between two methods was 83% (5/6). A total of 142 patients (90%) underwent radical resection, and seven metastasis or recurrence (5%) were detected during follow up. WHO classification grade 2 was the only risk factor predicting metastasis or recurrence in univariate and multivariate analysis (HR 8.81, 95% CI 1.76-44.11, p = 0.008).

Conclusions EUS-guided fine needle biopsy for small PNEN may be recommended to predict the malignant potential of the tumor by providing WHO classification.