Pulmonary neuroendocrine carcinoid tumors: Is there a predictive role to the Ki 67 index?

There are several factors predicting evolution in carcinoid tumors (CT) to date including the Ki67 role.

The aim of this study is to identify a KI67 cut-off point for a population of CT and determine its prognostic implication in global and disease-free survival.

Hematoxylin-eosin slides of 102 CT were revised. The percentage of cells expressing Ki 67 was determined manually.

The variables were compared with the t-test or the Wilcoxon test according to their distribution, the categorical ones with Chi-square or Fisher's test. The best cut-off point was established by constructing receiver operating characteristic curves, then using that value as a dichotomous variable.

72 typical carcinoids (TC) and 30 atypical carcinoids (AC) were analyzed; 66% were female. Median age (TC 38 vs. AC 51, P = 0.001), Ki67 expression (TC 0.63 vs. AC 2, P = 0.003), tumor size (TC 2.5 vs. AC 2.6, P = 0.001), the percentage relapse (TC 3.4% vs. AC 23%, P = 0.006), and the number of deaths (TC 1 vs. AC 4, P = 0.042) were significantly higher in the AC subgroup. The best cut-off point for Ki 67 was 0.755 (area under the curve AUC 0.564, 95% confidence interval 0.270-0.857), with no significant differences found in the disease-free and overall survival curves when considering values < or ≥ at the established cut-off point. The best cut-off point of the Ki-67 when exclusively analyzing AC was 1.18. When using this value as a predictive variable, a marginal statistical association was observed between Ki-67 expression, mortality (P = 0.077), and the frequency of relapses (P = 0.054).

Histological type is the best predictor of prognosis in the carcinoid tumor group. In the AC subgroup, the marginal association between mortality, frequency of relapses and Ki values 67 ≥ 1.18 has clinical relevance future analyses are required to determine the real predictive value of this variable.