Pain flare in patients with bone metastases after palliative radiotherapy--a nested randomized control trial

Short-course radiotherapy is a common treatment for the palliation of painful osseous metastases. Pain flare can be problematic, but its incidence has previously not been well-documented. The objectives of this study were to determine (1) the incidence of pain flare after palliative radiation for painful osseous metastases, and (2) whether single-fraction radiotherapy increases the risk of pain flare.

Patients accrued to a prospective randomized control trial comparing 8 Gy in one fraction to 20 Gy in five fractions (the Canadian Bone Metastasis Study) were approached to fill out a daily pain and analgesia diary for the 7 days post-radiotherapy. Patients assessed their average pain at the index site using the Present Pain Intensity (PPI) scale of the McGill-Melzack pain questionnaire and recorded their daily analgesic medications, which were translated into an analgesic score. Pain flare was defined as a two-point increase in the PPI with no decrease in analgesic score or a 50% increase in analgesic score with no decrease in PPI on at least two consecutive days.

Forty-seven patients agreed to fill out the diary and 44 (94%) completed it. Fifteen of 44 (34.1%) patients experienced a pain flare that lasted a median of 3 days. Ten of 23 (43.5%) and 5/21 (23.8%) of patients who received 8 Gy and 20 Gy had a pain flare, respectively.

Pain flare is common after palliative radiotherapy for osseous metastases and patients receiving single fraction radiotherapy may be at higher risk. Further study is warranted to determine predictors and preventive interventions.