Sporadic Small (≤20?mm) Nonfunctioning Pancreatic Neuroendocrine Neoplasm: is the Risk of Malignancy Negligible When Adopting a More Conservative Strategy? A Systematic Review and Meta-analysis

摘要

Abstract Background The management of small (≤20?mm), nonfunctioning pancreatic neuroendocrine neoplasms (pNENs) remains under debate. The European Neuroendocrine Tumor Society guidelines advocate the possibility of a conservative approach. Methods A systematic literature search was conducted to identify all studies comparing the risk of malignancy in small pNENs with respect to large ones (20?mm). Malignancy was defined based on the presence of nodal metastases. Distant metastases, tumor grading (G2–3), vascular microscopic invasion, stage III-IV, and overall and disease-free survival also were evaluated. The data were reported in two ways: using the risk difference (RD) and the likelihood of being helped or harmed (LHH). Results The search identified only 6 eligible studies with an overall population of 1697 resected pNENs: 382 (22.5%) small and 1315 (77.5%) large. The RD of lymph nodal metastases was ?0.26 (95% confidence interval (CI): ?0.31 to ?0.22; P ??0.001). The LHH was 0.34, suggesting that the risk of leaving a malignancy during follow-up due to the adoption of a conservative strategy was three times higher than the benefits. The risk difference of distant metastases, G3 lesions, G2–G3 lesions, stage III/IV, microscopic vascular invasion, death, and recurrence of the disease were lower in small NF-PNETs than large ones. The related LHH values suggested that a watch-and-wait policy never provided a benefit. Conclusions Even if the malignancy rate in sporadic, small pancreatic neuroendocrine neoplasms was lower than in large ones, this difference did not justify a watch-and-wait policy.