| Symptom clusters are stable groups of interrelated symptoms occurring simultaneously. Research on symptom clusters may yield helpful findings for improving symptom assessment/management strategies. This study aimed to identify treatment-related symptom clusters in breast cancer patients and to examine the influence of selected demographic/clinical variables (age, race, employment status, marital status, comorbid conditions, treatment modality, disease stage, and baseline physical performance status) on symptom clusters. A secondary analysis of a sample of 282 breast cancer patients who underwent chemotherapy or radiation therapy was conducted. Factor analyses of common oncologic treatment-related symptoms were done for selected treatment time points. Although specific symptoms within symptom clusters were not identical across time points, symptoms had a tendency to cluster into two groups: a psycho-neurological cluster and an upper gastrointestinal cluster. The two clusters were relatively independent of each other. The clustering pattern (factor structure) was generally replicable across the treatment trajectory. The pattern was also generally replicable in most subgroups formed by selected demographic/clinical variables across treatment time points, indicating that such variables did not significantly influence symptom clustering. However, after initiating cancer treatment, the clustering pattern in the full sample was not replicable in treatment modality subgroups. The pattern found in the full sample was very similar to that in the chemotherapy group, not the radiation group. Symptoms in each cluster had statistical relationships with each other, and these were generally maintained in subgroups formed by clinical/demographic variables. The influence of selected variables on the intensity of symptoms in a cluster was then examined by multiple regression analysis. Baseline physical performance status was a consistently significant predictor across time points for the psycho-neurological cluster. Age and treatment modality were consistently significant predictors for the upper gastrointestinal cluster across time points. Younger patients, chemotherapy patients, and patients with more limitations in physical performance status at baseline had more intense symptoms. Future research should elucidate the clinical/theoretical implications of symptom clusters identified by this study through the development of effective assessment/intervention strategies for symptom clusters. Finally, the possibility that symptoms in a cluster share a biological basis should be examined to develop symptom management strategies. |
