Hypokalaemia and hypercortisolaemia at diagnosis are negative prognostic factors: a retrospective analysis of the medical management of ectopic Cushing syndrome

<h3>Background</h3> Ectopic Cushing syndrome (ECS), related to neuroendocrine neoplasms (NENs), is a rare condition with high morbidity and mortality. We hypothesised that both the severity of hypercortisolaemia and hypokalaemia correlates with prognosis. <h3>Materials and methods</h3> Fifty-five patients with ECS (37 females), with a mean age of 54 ± 14 (standard deviation) years were identified in our database for further analysis of clinical parameters, biochemical data, symptomatic treatment and outcome. <h3>Results</h3> Twenty-eight patients had bronchial, 16 pancreatic, 4 thymic and 1 a rectal NEN. In six patients, the primary tumour was unknown. The proliferation index, Ki-67, was ≤20% in 31 patients and hypokalaemia correlated negatively with Ki-67 (<i>P</i> = 0.043). Severe hypokalaemia at diagnosis (<2.5 mmol/l) was found in 50% of the patients. Hypokalaemia and high doses of potassium substitution were associated with shorter overall survival (<i>P</i> = 0.009 and <i>P</i> = 0.019, respectively). However, only severe hypercortisolaemia remained an independent negative factor for survival in multivariate analysis (<i>P</i> = 0.042). Potassium substitution was required in 87% of patients and the dose was positively correlated to baseline hormone levels including urinary free cortisol (<i>P</i> < 0.001), s-cortisol (<i>P</i> < 0.001) and adrenocortical hormone (ACTH) (<i>P</i> = 0.016). Steroidogenesis inhibitors (SIs) were used as initial treatment in 46 patients to improve symptoms. However, within 1 month, 17 proceeded to bilateral adrenalectomy and 3 died. <h3>Conclusions</h3> We conclude that only hypercortisolaemia was independently prognostic for shorter survival. Furthermore, we suggest that hypercortisolaemia, especially in combination with severe hypokalaemia (<2.5 mmol/l), indicates an acute life-threatening situation. For these patients, immediate actions should be considered to reduce cortisol levels and bilateral adrenalectomy should be discussed upfront.