Symptom clusters in patients with advanced cancers

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Abstract
It has been observed that certain cancer symptoms frequently occur together. Prior research on symptom patterns has focused mainly on inpatients, early stage cancers, or a single cancer type or metastatic site. Our aim was to explore symptom clusters among outpatients with different advanced cancers. Symptom scores by the Edmonton Symptom Assessment Scale (ESAS) were routinely collected for patients attending the Oncology Palliative Care Clinics at Princess Margaret Hospital from January 2005 to October 2007. Principal component analysis (PCA) was performed for the entire patient cohort and within specific disease sites to determine inter-relationships of the nine ESAS symptoms. A total of 1,366 patients was included: 682 (50%) were male and 684 (50%) were female. The median age was 64 years (range 18 to 74 years). The most common primary cancer sites were gastrointestinal (27%), lung (14%), and breast (11%). The three most distressful symptoms were fatigue, poor general well-being, and decreased appetite. PCA of symptoms for the entire patient cohort revealed two major symptom clusters: cluster 1 included fatigue, drowsiness, nausea, decreased appetite, and dyspnea, which accounted for 45% of the total variance; cluster 2 included anxiety and depression, which accounted for 10% of the total variance. There was high internal reliability in the clusters (Cronbach’s alpha coefficient ∼0.80). PCA of symptoms within the various primary cancer sites revealed differences in the pattern of symptom clusters. In patients with advanced cancers, distinct symptom clusters can be identified, which are influenced by primary cancer site. Treatments directed at symptom clusters rather than individual symptoms may provide greater therapeutic benefit. Further prospective studies are warranted in order to develop more effective targeted palliative interventions for the advanced cancer patient population.