CUP syndrome in neuroendocrine neoplasia: Analysis of risk factors and impact of surgical intervention

Background: Neuroendocrine neoplasia (NEN) with unknown primary site (NEN-CUP tumors) may have a poor prognosis. We evaluated the clinical presentation, therapy, outcome, and risk factors for adverse outcomes in patients who had these tumors. Methods: In 243 patients who had NEN, a retrospective review was performed in 38 patients who had NEN-CUP tumors. The 38 patients who had NEN-CUP tumors were evaluated in three groups: group 1 (surgery; primary tumor detected; ten patients); group 2 (surgery; no primary tumor detected; ten patients); and group 3 (no surgery; 18 patients). Risk factors were evaluated with univariate and multivariate analyses. Results: Most patients who had NEN-CUP tumors [32 patients (84 %)] had World Health Organization (WHO) performance score of 0 or 1, and most tumors [24 patients (63 %)] were well differentiated (WHO grade, G1 or G2; Ki-67 index, ≤20 %). Univariate analysis showed that greater survival was significantly associated with lower patient age, lower WHO performance score, lower WHO grade, lower number of metastatic sites, treatment with surgery, and no treatment with chemotherapy. Multivariate analysis showed that low WHO performance score (hazard ratio 7.63, 95 % confidence interval (CI) 2.63-22.19) and treatment with surgery (hazard ratio 0.10, CI 0.028-0.381) were significant independent predictors of improved survival. Conclusions: In patients with NEN-CUP tumors, surgical treatment is an independent predictor of better survival. Therefore, surgical treatment may be indicated in patients with good general health status and well-differentiated NEN-CUP tumors.