Relationship between Pain Scores and EORTC QLQ-C15-PAL Scores in Outpatients with Cancer Pain Receiving Opioid Therapy

Cancer pain is one of the most frequent and distressing symptoms associated with cancer and has a serious impact on the QOL of patients. However, inadequate pain treatment has also been reported in outpatients with cancer pain. The aims of this study were (1) to evaluate the relationship between pain intensity using the Numerical Rating Scale (NRS) and QOL scores using the Japanese version of the European Organization for Research and Treatment of Cancer (QOL Questionnaire Core 15 for Palliative Care (QLQ-C15-PAL)), and (2) to investigate their association with various pain patterns, especially with baseline and breakthrough pain. Forty outpatients who were receiving opioid therapy and obtained informed consent participated. We collected a total of 222 pharmacist consultations during the study period. Global QOL scores and pain scores (PA) in the QLQ-C15-PAL (PA score, 0-100) at the first visit were significantly correlated with worst pain intensity. In addition, the scores for the worst pain were significantly correlated with not only physical functioning scores but also with emotional functioning scores. The correlations between the worst pain NRS and PA scores were positive. Specifically, patients tended to report large variability of NRS scores when the PA score was less than 40 and also when they exhibited pain patterns with "baseline and breakthrough cancer pain in the same day" or "baseline pain throughout the day." Reducing the worst pain NRS and relieving breakthrough pain appear to be important measures to improve the QOL of outpatients receiving opioid therapy for cancer pain.