Review: Symptom clusters: myth or reality?

Abstract

Clinical experience suggests that many symptoms occur together. In this paper, we examine the rationale and evidence base for symptom clusters in different medical fields, particularly the cluster phenomenon in cancer. Cancer symptom clusters are a reality. Various symptoms that cluster clinically have also been verified statistically. Specific clusters such as nausea-vomiting, anxiety-depression, and cough-dyspnea are evident on both clinical observation and in research investigation. Fatigue-pain and fatigue-insomnia-pain have also been demonstrated statistically as clusters. Another proposed cluster 'depression-fatigue-pain' seems relevant to clinical practice. Other clusters may serve only as theoretical models that illustrate possible common biological etiologies in cancer; they need to be validated in future research. Analysis of the literature is complicated by considerable inconsistencies across studies. Discrepancies between clinically defined and statistically obtained clusters raise important questions. We must consider the analytical techniques used, and how methodology might influence cluster occurrence and composition. Further research is warranted to establish universally accepted statistical methods and assessment tools for symptom cluster research.

Symptom Clusters in Advanced Cancer Patients: An Empirical Comparison of Statistical Methods and the Impact on Quality of Life

“…In addition, the fatigue-pain cluster strongly predicted health and all three aspects of functioning for every cancer site, consistent with previous research (32)(33)(34)(35). We found weak associations between depression and fatigue-pain across cancers, despite previous findings that fatigue-pain-depression were associated with reduced physical function and co-occurred in clinical practice (33).…”

“…Although Aktas et al (34) suggested the fatigue-pain cluster is likely influenced by cancer site, we observed it across cancer sites, supporting the role of pro-inflammatory cytokines as a common underlying mechanism. Although pharmacologic treatments have been effective in improving cancer-related fatigue in patients with advanced cancer (42), the strength of the relation between systemic inflammation and SCs needs to be examined further within the context of trials exploring interventions targeted to pro-inflammatory cytokine pathways.…”

Differences in Composition of Symptom Clusters Between Older and Younger Oncology Patients

“…12,33,34 Although the sample in this study represents a heterogeneous group of patients in terms of tumor sites and stages of disease, all patients were receiving active treatment for their cancer. Moreover, as older and younger patients were recruited as part of the same study using the same instrument and data collection procedures, the similarities and differences in patterns of symptom clusters observed in this study raise important theoretical and practical considerations that warrant further investigation.…”

“…These clusters are similar to those identified clinically and from empiric evidence in patients with various types of cancers. 34 Such clusters are typically viewed as being common responses to the disease process and to the multifaceted experience of undergoing cancer treatment. However, although some concordance existed, notable differences were found between older and younger patients in terms of the specific symptoms within each of these common clusters.…”

Advancing Symptom Science Through Symptom Cluster Research: Expert Panel Proceedings and Recommendations

“…Following the challenge from the Symptom Management Research Group at the University of California, San Francisco, to the scientific community to consider the concept of a "symptom cluster" (17) and the publication of a state of the science lecture on symptom cluster research in oncology patients (18), a number of review articles have examined the conceptual and methodological issues associated with defining the characteristics of a symptom cluster (19)(20)(21)(22)(23)(24)(25)(26)(27)(28). Three topics were the foci for the discussion of the "state of the science" in the area of defining characteristics of symptom clusters, namely conceptual issues, empiric identification of symptom clusters, and changes in symptom clusters over time.…”