Time Course of Pain Relief in Patients Treated With Radiotherapy for Cancer Pain

OBJECTIVES: The purpose of this prospective study was to analyze time course of pain relief by radiotherapy for cancer pain. METHODS: A total of 91 patients with painful bone metastases were treated by radiotherapy with a median total dose of 46 Gy. Pain of the irradiated site was assessed using a numerical rating scale (pain score: 0 to 10) once a week from the beginning of radiotherapy (day 1) for about 5 weeks. RESULTS: In time course analysis of the 91 cases, the mean (+/-SD) pain scores at day 5, day 12, day 19, day 26, day 33, and day 40 were 7.8 (+/-1.6), 5.3 (+/-2.5), 3.5 (+/-2.5), 2.4 (+/-2.5), 1.6 (+/-2.1), and 1.1 (+/-1.9), respectively, and mean pain score was significantly reduced with time from the start of radiotherapy (P<0.001: repeated measure ANOVA). Mean pain score was significantly reduced every week by d33 (P<0.05: d5 vs. d12, d12 vs. d19, d19 vs. d26, and d26 vs. d33). Complete pain relief was obtained in 45/91 (49%) cases, and partial (> or =50%) pain relief was obtained in 83/91 (91%) cases. The mean time to obtain 50% pain relief was 13 days. The mean time to obtain complete pain relief (n=45) was 24 days. Doses of analgesics were reduced in 28/64 (44%) cases at the end of radiotherapy. DISCUSSION: Telling approximate time course of pain relief seems to reduce patients' anxiety, and knowing time course of pain relief seems to be useful to determine optimal dose of analgesics that changes according to the course.