Relationship between background cancer pain, breakthrough pain, and analgesic treatment: a preliminary study for a better interpretation of epidemiological and clinical studies.

Background: The different operational definitions of breakthrough cancer pain (BTcP) has generated unclear epidemiological data.

Methods: A consecutive sample of patients was categorized on the basis of their background pain intensity, background analgesic treatment, and the presence of BTcP.

Results: A total of 265 patients were surveyed; 117 patients had background pain and 91 patients presented peaks of pain intensity distinguishable from background pain. Of 117 patients with background pain, 49 patients were re-assessed after optimization of background analgesia (T1) within a mean of 8.2 days. Pain intensity significantly decreased in comparison with values recorded at admission (p < 0.0005); 75.5% of these patients had BTcP episodes, with a significant decrease in the number BTcP episodes in comparison with T0 (p < 0.0005). The mean BTcP intensity was significantly lower in comparison with T0 (p < 0.0005). Finally, the mean duration of untreated BTcP episodes decreased significantly in comparison with T0 (p = 0.016). After optimization of analgesic therapy, most patients with moderate or severe background pain receiving opioids for moderate pain, patients with moderate or severe pain receiving strong opioids, and patients with moderate or severe pain receiving no opioids moved to the group of patients with mild pain receiving strong opioids. The difference was significant (p = 0.022).

Conclusion: Patients having good pain control after optimization of the analgesic regimen may have a decrease in number, intensity, and duration of BTcP, although the general prevalence of BTcP remains unchanged.