The clinicopathologic and operative characteristics of patients with small nonfunctioning pancreatic neuroendocrine tumors

Abstract

Background: Incidentally detected, small nonfunctioning pancreatic neuroendocrine tumors (NF-PNETs) are increasingly diagnosed on imaging modalities. This retrospective investigation evaluated the clinicopathologic characteristics and perioperative and oncologic outcomes in patients with small NF-PNETs undergoing curative resection.

Methods: The medical records of 444 patients who underwent pancreatic resection for NF-PNETs at a single, large-volume institution between January 2000 and December 2018 were retrospectively reviewed. Patients were divided into those with small (=2 cm) and large (>2 cm) tumors based on the largest tumor diameter on preoperative computed tomography (CT). Outcomes were also evaluated in subgroups of patients with small NF-PNET who did and did not undergo lymphadenectomy.

Results: Of the 444 patients with NF-PNETs, 195 (43.9%) had small (=2 cm) and 249 (56.1%) had large (>2 cm) NF-PNETs. The rate of parenchyma-preserving surgery (14.4% vs. 7.2%, p = 0.014) and the ratio of spleen preservation for left-sided pancreatectomy (65.6% vs. 38.3%, p < 0.001) were higher in the small NF-PNET group. Size on CT >2 cm (p < 0.001, hazard ratio [HR]: 5.836, 95% confidence interval [CI]: 2.474-13.769), presence of perineural invasion (p < 0.001, HR: 3.025, 95% CI: 1.640-5.577), World Health Organization (WHO) Grade 2 (p = 0.007, HR: 2.861, 95% CI: 1.325-6.176), and WHO Grade 3 (p < 0.001, HR: 11.537, 95% CI: 5.282-25.199) were independent predictors of disease-free survival (DFS). DFS did not differ significantly in patients with small NFPNETs who did and did not undergo lymphadenectomy (p = 0.886).

Conclusions: Assessment of long-term oncologic outcomes suggests that surgical resection may cure small NF-PNETs. Minimally invasive surgery and organ-preserving surgery are acceptable treatment options for select patients with small NF-PNETs. The effect on survival outcomes of lymph node dissection for small NF-PNETs remains unclear.