title: 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.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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)
  
  
  CONCLUSIONS
  These findings confirm the high prevalence of BTcP and substantial undertreatment and identify a few factors associated with prevalence and prognosis.
authors.affiliation: Center for the Evaluation and Research on Pain (CERP), Istituto di Ricerche Farmacologiche Mario Negri, University of Milano, Via La Masa 19, Milan, Italy.
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Greco
authors.forename: Oscar
authors.initials: O
authors.lastname: Corli
authors.forename: Mauro
authors.initials: M
authors.lastname: Montanari
authors.forename: Silvia
authors.initials: S
authors.lastname: Deandrea
authors.forename: Vittorina
authors.initials: V
authors.lastname: Zagonel
authors.forename: Giovanni
authors.initials: G
authors.lastname: Apolone
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D007558:Italy; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications*; D010146:Pain / Q000188:drug therapy* / Q000453:epidemiology* / Q000209:etiology; D010147:Pain Measurement; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D011795:Surveys and Questionnaires; D016896:Treatment Outcome