Interference with daily functioning by breakthrough pain in patients with cancer

Purpose: To investigate the association between quality of life (QOL) and breakthrough cancer pain (BTCP) intensity in patients who met the commonly accepted definition of BTCP. Methods: This study was a subset analysis of a South Korean multicenter, non-interventional, cross-sectional, nationwide survey. Participants were recruited from March 2016 to December 2017. BTCP was defined as a controlled background pain of less than a numeric rating scale (NRS) of 3 and any flare-up pain intensity. Pain intensity data were collected using the Brief Pain Inventory (BPI), which includes an interference assessment of the affective and physical domains. Patients were categorized by BTCP intensity into mild (NRS 1–3), moderate (4–6), and severe (7–10) groups. Results: Of the 969 screened patients with cancer, 679 had ≤ NRS 3 background pain, of whom 438 completed the BPI. Of these 438 patients, 40, 204, and 194 were in the mild, moderate, and severe BTCP groups, respectively. The median NRS of BTCP was 6.0 (interquartile range = 5.0–8.0). Patients with moderate-severe BTCP had significantly higher interference with daily functioning (IDF) scores than did mild BTCP patients (3.3 vs. 5.7; p < 0.01). Both domains of IDF were significantly hampered proportionally by increased BTCP intensity (p < 0.001). The median total IDF scores of the no, moderate, and severe BTCP groups were 3.3, 5.0, and 6.9, respectively. Furthermore, IDF depended on BTCP intensity, duration, and frequency (p < 0.01) but not on pain type and cause. Conclusion: An increase in BTCP intensity is likely to result in IDF, regardless of the cause or type of BTCP.