An investigation into the incidence of pain flare in patients undergoing radiotherapy for symptomatic bone metastases

Introduction External Beam Radiotherapy (EBRT) is a recognised intervention for symptomatic pain relief from bone metastases. Pain flare is a reported EBRT toxicity, described in 16-41% of steroid-naïve patients. This study aimed to determine incidence and duration of pain flare amongst patients within one Oncology Centre. Methods Patients receiving EBRT for bone metastases were recruited to a prospective cohort study. Baseline pain scores and a daily pain/analgesia diary were recorded during EBRT and for 14days thereafter. Pain flare was defined as a two-point increase on a pain scale or 25% increase in analgesia intake, with a return to baseline. Results Of the thirty-two participants, 69% (n=22) completed the diary. 41% (n=9) patients experienced pain flare, the median duration being 3 days. Of the evaluable patients, 55% (n=12) were male, 45% (n=9) female. The median age was 73years, (range 40-83). The common primary sites of disease were Breast (32%) and Prostate (32%), with other sites making up the remaining 36%. The most frequent EBRT site was the spine (63%), with other treatment sites including pelvis (23%) and extremities (14%). EBRT regimes were restricted to 20Gy in 5 treatments, received by 32% (n=7) of patients and 8Gy in 1 treatment (68% (n=14)). Of these two regimes, pain flare was reported by 29% and 47% respectively. Conclusion Pain flare is a common toxicity of EBRT for bone metastases. Taking the small sample size into consideration, the incidence and duration of pain flare in patients within this single-centre study are comparable with those found in international studies. Key Word