A longitudinal study of pain variability and its correlates in ambulatory patients with advanced stage cancer

BACKGROUND: Although pain is common among patients with advanced cancer, little is known about longitudinal variability in pain intensity. For this report, the authors examined variability in pain intensity over 24 months among ambulatory patients with advanced stage cancers, associations between patient characteristics and within-patient pain variability, and the relation of pain variability to overall survival. METHODS: The sample comprised 949 patients with solid tumors who received care and reported pain scores in at least 3 different months within 24 months of their initial stage IV diagnosis during the period from 2004 to 2006. Pain intensity was measured using a scale ranging from 0 (no pain) to 10 (worst pain). Pain variability was defined as the standard deviation of the maximum monthly pain scores and was dichotomized at the 50th percentile into high and low variability groups. RESULTS: Considerable between-patient differences in pain variability (range, 0-5.77) were observed. Nonwhites, patients with a stage IV cancer diagnosed within the previous 3 months, and those with moderate or severe pain at baseline were more likely to experience high pain variability. Although patients with head and neck cancer generally had the highest pain variability, the intensity of their pain typically decreased over the disease course. High pain variability with worsening pain trajectory was associated with increased risk of death. CONCLUSIONS: Longitudinally, pain intensity was highly variable among patients with stage IV cancer. Minority patients, newly diagnosed patients, patients with head and neck cancer, and patients with moderate or severe pain at baseline were at higher risk of large fluctuations in pain intensity.