To determine the true incidence of brain metastases in atypical lung neuroendocrine tumors and explore factors that increase the risk of intracranial disease

Abstract

Introduction: Lung neuroendocrine tumors (NETs) make up 25% of all NETs. Typical carcinoid (TC) and atypical carcinoid (AC) account for 2% and 0.2% of all lung NETs respectively, and AC tend to be more aggressive. Although both can metastasise, AC are more likely; common sites include bone and liver. Currently, brain imaging is not included in the work-up of TC/AC, as <5% of cases are thought to develop brain metastases (BM). However, evidence suggests this may be an underestimate. Identifying BM would inform management and could improve prognosis. Thus, evaluating the incidence in TC/AC is needed to ascertain whether there is justification for baseline brain imaging. Furthermore, Ki-67 could be useful as a predictive tool. Aim(s): To review the incidence of BM in TC/AC to determine whether there is justification for routine brain imaging and to explore factors which could increase the risk of BM. Materials and methods: Single site, retrospective analysis of 287 patients with TC/AC over a 13-year period. Incidence of BM (as detected on CT/MRI), at diagnosis or during the course of the disease, was reviewed. Results: None of the 215 TC patients developed BM, whereas 8 out of 72 (11.1%) with AC did; 50% of these were present at diagnosis. 13.04% of AC with BM had evidence of both bone and liver involvement. 75% of AC with BM had Ki-67 expression >15%. Conclusion: Over 10% of the AC developed BM, half of which were present at diagnosis. This provides convincing evidence of the need for baseline brain imaging in AC, particularly for patients with Ki-67 expression >15% or with bone and liver involvement, as these factors were associated with increased risk. Early detection and treatment of BM can improve outcomes