Epidemiology and pattern of care of breakthrough cancer pain in a longitudinal sample of cancer patients: results from the Cancer Pain Outcome Research Study Group.

Breakthrough cancer pain (BTcP) is a frequent event in cancer patients, with a prevalence from 19\% to 95\%. The reasons for such variability are explained by several factors, including different definitions across studies. In the framework of a wider initiative, we have analyzed the epidemiology of BTcP and identified factors associated with the pattern of care.This study reports the results from a multicenter, prospective, nonrandomized, longitudinal study carried out in Italy between 2006 and 2007 on patients with cancer and pain. Transient exacerbations of pain were assessed with 3 different questions, and 1 composite variable to operationally define BTcP was then used as main outcome. After univariate analysis, a logistic model was also fitted to identify prognostic and predictive factors.One hundred and ten centers recruited 1801 cases of which 40.3\% had BTcP at baseline. Most patients did not receive rescue therapy at the time of study inclusion. Univariate analysis identified several associations with clinical variables. A strong association has been also found with the type of recruiting centers, with oncologic wards reporting a somewhat lower proportion of patients with BTcP (-30\%) when compared with palliative centers. Patients with BTcP had a high probability of dying (OR=1.4, 95\% CI: 1.1-1.7, P-value 0.006) and to change of the opioid with another for analgesic failure or for side effects (OR=1.4, 95\% CI: 1.0-1.9, P-value 0.040)These findings confirm the high prevalence of BTcP and substantial undertreatment and identify a few factors associated with prevalence and prognosis.