Symptom clusters in cancer patients with bone metastases

The purpose of this study is to explore whether bone pain "clusters" with other symptoms in patients with bone metastases.

Patients with bone metastases referred to a palliative radiotherapy clinic were asked to rate their symptom distress using the Edmonton Symptom Assessment Scale (ESAS). Analgesic consumption during the previous 24 h was captured at initial consultation. To determine interrelationships between symptoms, a principal component analysis (PCA) with "varimax rotation" was performed on the nine ESAS symptoms. This study defined a "symptom cluster" as two or more symptoms that occur together, are stable, and are relatively independent of other clusters. Patients were followed 1, 2, 4, 8, and 12 weeks post-radiation treatment by telephone. Statistical analysis was performed at each time point for both responders and nonresponders to radiation (response was defined in accordance to the International Bone Metastases Consensus Working Party).

Five hundred eighteen patients with bone metastases provided complete baseline data using the ESAS. The four most prevalent symptoms were poor sense of well-being (93.5%), fatigue (92.3%), pain (84.1%), and drowsiness (81.8%). Three clusters were identified and accounted for 66% of the total variance at baseline. Cronbach's alpha coefficient demonstrated high internal reliability in the clusters, with a coefficient ranging from 0.61 to 0.81. It was observed that the clusters changed post-radiation in both responders and nonresponders and that pain clustered with different symptoms (or remained a separate symptom in responders). In nonresponders, three symptom clusters were consistently present, except in week 8.

Radiotherapy influenced the structure of symptom clusters in both responders and nonresponders. There was evidence that pain clustered out in responders of radiation to pain. It was found that pain clustered with fatigue, drowsiness, and poor sense of well-being at baseline. However, these findings must be heeded with caution, as more work is needed to clearly define symptom clusters and to understand the effects of radiation in the symptom experience of patients with bone metastases.