Lung carcinoids with high proliferative activity: Further support for the identification of a new tumor category in the classification of lung neuroendocrine neoplasms

Highly proliferative lung carcinoids (HPLC) have been recently reported but information about this subset remains scarce. Objectives: Clinical and pathological data of 630 patients with lung carcinoids (LC) referred to Gustave Roussy Institute (GR) and European Institute of Oncology (IEO) were retrospectively reviewed to select HPLC and analyze their frequency, behavior and compare their outcome to conventional LC with Ki-67 ≤ 20 % and mitotic count (MC)≤10/2 mm2. Materials and methods: Selection criteria were: diagnosis of LC confirmed by local pathologist, and available clinical and follow-up data. Patients with Ki-67 > 20 % and/or MC > 10/ 2 mm2 in primary or metastatic specimens were identified as HPLC. Results: 30/514 patients (6%) met the selection criteria of HPLC. Based on primary tumor evaluation, 22/25 (88 %) were classified as atypical carcinoids (AC). Median MC was 4.5/2 mm2 (1–11) 6/2 mm2 (3–15) in primary tumors and metastasis, respectively. Median Ki-67 was respectively 23 % (15–65) and 25 % (8–60). Recurrence rate was 66 % (12/18) in HPLC and 9 % (33/352) in conventional LC. Median RFS was 24 (10-NR) months in HPLC, 288 (141-NR) months in LC with Ki-67 index≤5 % and NR (148-NR) months in LC with Ki-67 6−20% (p < 001). Median OS was 203 (83-NR) months in LC with Ki-67 index≤5%, 101 (79-NR) months in LC with Ki-67 index 6−20 % and 53 (39-NR) months in HPLC (p = 002). Among 20 metastatic patients with HPLC, median PFS under platinum-based chemotherapy, everolimus, alkylating-based chemotherapy, FOLFOX and PRRT was 5.1 (95 % CI 0.7−9.4), 12.1(95 %CI 0.3−24), 6.8 (95 % CI 0−14.9), 10.2 (95 % CI 0.4−19.9) and 14.2 months (95 % CI 0-30) respectively. Best response was stable disease (SD) under platinum-based chemotherapy and partial response (PR) under alkylating-based chemotherapy and FOLFOX. Conclusion: This study confirms the existence and rarity of HPLC. Their characteristics and clinical behavior are more similar to LC rather than neuroendocrine carcinomas (NECs), suggesting that this entity could be managed accordingly