Endocrine paraneoplastic syndromes in patients with neuroendocrine neoplasms

Objective: Our aim was to assess the prevalence of endocrine paraneoplastic syndromes (EPNS) in neuroendocrine neoplasms (NENs) and estimate its impact on patient outcomes.

Design: This is a retrospective analysis of 834 patients with NENs (611 gastrointestinal, 166 thoracic, 57 of unknown and various other primary origin). We included 719 consecutive NEN patients treated at EKPA-Laiko Hospital, Athens, Greece and 115 patients with lung carcinoid (LC) treated at Uppsala University Hospital, Uppsala, Sweden. EPNS diagnosis was based on standard criteria.

Methods: Twenty-one patients with EPNS were detected: 16 with ectopic Cushing's syndrome (ECS), one with hypercalcaemia due to parathyroid hormone-related protein (PTHrP) secretion, three with hypercalcitonaemia and one patient with dual secretion of calcitonin and beta-human chorionic gonadotropin (β-HCG). All tumours were well-differentiated; 10 patients had Stage IV disease at diagnosis.

Results: The prevalence of EPNS in the Greek cohort was 1.9%, whereas that of ECS among LC patients in both centres was 6.7%. Median overall survival (OS) for patients with EPNS was 160.7 months (95%CI, 86-235.4) and median event-free survival (EFS) was 25.9 months (95%CI, 0-57.2). Patients presenting with EPNS prior to NEN diagnosis had longer EFS compared to patients with synchronous or metachronous EPNS (log-rank P = 0.013). Patients with ECS of extra-thoracic origin demonstrated shorter OS and EFS compared to patients with ECS of lung or thymic origin (log-rank P = 0.001 and P < 0.001, respectively). LC patients with and without ECS were comparable in 5-year and 10-year OS rates (66.7% and 33.3% versus 89.8% and 60.2%, respectively; 95%CI [189.6-300.4 months], log-rank P = 0.94) and in median EFS, 67 versus 183 months, 95%CI [50.5-207.5], log-rank P = 0.12).

Conclusion: EPNS are relatively rare in patients with NENs and mainly concern well-differentiated tumours of the foregut. Among patients with EPNS, LC-related ECS may not adversely affect patient outcomes when diagnosed prior to NEN and effectively been treated.