Disease-specific quality of life evaluation and its determinants in Cushing's syndrome: what have we learnt?

Cushing's syndrome (CS) has a considerable negative impact on patient health-related quality of life (HRQoL). Two disease-specific instruments (the CushingQoL and the Tuebingen CD-25 questionnaire) are now available to assess the impact of the disease and its treatment on HRQoL. The purpose of this review was to summarize the characteristics of the studies which have used these two instruments to date and summarize their findings regarding (a) the determinants of disease-specific HRQoL in patients with CS and (b) the impact of treatment for CS on disease-specific HRQoL. A total of 7 studies were identified, 5 with the CushingQoL and 2 with the Tuebingen CD-25. Most were observational studies, though the CushingQoL had been used in one randomized clinical trial. In terms of clinical factors, there was some evidence for an association between UFC levels and disease-specific HRQoL, though the presence and strength of the association varied between studies. There was also some evidence that a more recent diagnosis of CS could lead to poorer HRQoL, and that length of time with adrenal insufficiency may also affect HRQoL. There was no evidence for an impact on disease-specific HRQoL of etiology or of the clinical signs and symptoms associated with CS, such as bruising, rubor, and fat deposits. One factor which did have a significant negative effect on HRQoL was the presence of depression. No clear picture emerged as to the effect of demographic variables such as age and gender on HRQoL scores, though there was some evidence for poorer HRQoL in female patients. As regards treatment, the two interventions studied to date (transsphenoidal surgery and pasireotide) both showed significant gains in HRQoL, with moderate to large effect sizes. This type of review is useful in summarizing knowledge to date and suggesting future research directions.