A Multimodal Biomarker Predicts Dissemination of Bronchial Carcinoid

Abstract

Background: Curatively treated bronchial carcinoid tumors have a relatively low metastatic potential. Gradation into typical (TC) and atypical carcinoid (AC) is limited in terms of prognostic value, resulting in yearly follow-up of all patients. We examined the additional prognostic value of novel immunohistochemical (IHC) markers to current gradation of carcinoids. Methods: A retrospective single-institution cohort study was performed on 171 patients with pathologically diagnosed bronchial carcinoid (median follow-up: 66 months). The risk of developing distant metastases based on histopathological characteristics (Ki-67, p16, Rb, OTP, CD44, and tumor diameter) was evaluated using multivariate regression analysis and the Kaplan−Meier method. Results: Of 171 patients, seven (4%) had disseminated disease at presentation, and 164 (96%) received curative-intent treatment with either endobronchial treatment (EBT) (n = 61, 36%) or surgery (n = 103, 60%). Among the 164 patients, 13 developed metastases at follow-up of 81 months (IQR 45−162). Univariate analysis showed that Ki-67, mitotic index, OTP, CD44, and tumor diameter were associated with development of distant metastases. Multivariate analysis showed that mitotic count, Ki-67, and OTP were independent risk factors for development of distant metastases. Using a 5% cutoff for Ki-67, Kaplan−Meier analysis showed that the risk of distant metastasis development was significantly associated with the number of risk predictors (AC, Ki-67 ≥ 5%, and loss of OTP or CD44) (p < 0.0001). Six out of seven patients (86%) with all three positive risk factors developed distant metastasis. Conclusions: Mitotic count, proliferation index, and OTP IHC were independent predictors of dissemination at follow-up. In addition to the widely used carcinoid classification, a comprehensive analysis of histopathological variables including Ki-67, OTP, and CD44 could assist in the determination of distant metastasis risks of bronchial carcinoids.

Keywords: Ki-67; distant metastases; immunohistochemistry; prognosis; pulmonary carcinoid.

Figure 1

Receiver operating characteristic (ROC) curves for Ki-67, mitotic count, CD44, and OTP. Panels (A–C) present ROC curves of individual ((A) Ki-67, p = 0.003, and mitotic count, p < 0.000; (B) CD44, p < 0.000, and OTP, p < 0.000)) and combined markers ((C) OTP, Ki-67, and mitotic count, p < 0.000) for distinguishing occurrence of distant metastases (n = 13) from no occurrence of distant metastatic disease during follow-up.

Figure 2

Immunohistochemical analysis of Ki-67 (A), and CD44 and OTP (B) expression in the studied patient categories; significance was determined using the Mann-Whitney U test (A) and Chi-Squared or Fisher’s Exact test (B); ns = not significant; ** p < 0.01; *** p < 0.001. ns: p > 0.05.

Figure 3

Distant metastasis-free survival curves estimated using Kaplan–Meier method for three biomarker profiles; + (favorable) profile: Ki-67 < 5%, mitotic count < 2 per 2 mm², OTP and CD44 positivity;—(unfavorable) profile: Ki-67 ≥ 5%, mitotic count ≥ 2 per 2 mm², and loss of OTP and/or CD44 expression; ± (neutral) profile: one or two characteristics of (un)favorable profile; * excluding nine patients due to stage IV disease at diagnosis (n = 7) or missing CD44 values (n = 2).

Figure 4

Prognostically favorable profile in histology and immunohistochemistry. (A). HE (40×) showing carcinoid with a well differentiated neuroendocrine morphology without mitoses. (B). Immunohistochemistry for Ki-67 (20×) showing a proliferation index of <3% in tumor cells. (C). Immunohistochemistry for CD44 (20×) with retained strong cytoplasmatic and membranous staining in the tumor cells. (D). Immunohistochemistry for OTP (20×) showing a retained nuclear staining in the tumor cells.

Figure 5

Unfavorable profile in histology and immunohistochemistry. (A). HE (40×) showing carcinoid with a mitotic hotspot with readily visible two mitotic figures in one HPF (arrows). (B). Immunohistochemistry for Ki-67 (20×) showing a proliferation index of >5% in tumor cells. (C). Immunohistochemistry for CD44 (20×) showing loss of cytoplasmatic and membranous staining in the tumor cells (D). Immunohistochemistry for OTP (20×) showing loss of nuclear staining in the tumor cells.