Symptom clusters in patients with advanced cancer: a systematic review of observational studies.

Context. Advanced cancer patients typically experience multiple symptoms, which may influence patient outcomes synergistically. The composition of these symptom clusters (SCs) differs depending on various clinical variables and the timing and method of their assessment. Objectives. The objective of this systematic review was to examine the composition, longitudinal stability, and consistency across methodologies of common SCs, as well as their common predictors and outcomes. Methods. A search of MEDLINE, CINAHL, Embase, Web of Science, and PsycINFO was conducted using variants of symptom clusters, cancer, and palliative care. Results. Thirty-three articles were identified and reviewed. Many SCs were identified, with four common groupings being anxiety-depression, nausea-vomiting, nausea-appetite loss, and fatigue-dyspnea-drowsiness-pain. SCs in most cases were not stable longitudinally. The various statistical methods used (most commonly principal component analysis, exploratory factor analysis, and hierarchical cluster analysis) tended to reveal different SCs. Different measurement tools were used in different studies, each containing a different array of symptoms. The predictors and outcomes of SCs were also inconsistent across studies. No studies of patient experiences of SCs were identified. Conclusion. Although the articles reviewed revealed four groups of symptoms that tended to cluster, there is limited consistency in the way in which SCs and variables associated with them are identified. This is largely due to a lack of agreement about a robust, clinically relevant definition of SCs. Future research should focus on patients' subjective experience of SCs to inform a clinically relevant definition of SCs and how they are managed over time.