Pain Flare After Single Fraction Radiotherapy for Symptomatic Bone Metastases—Do We Have a Predictive Model?

Background The COVID‐19 pandemic reintroduced single‐fraction radiotherapy for symptomatic bone metastases due to its efficiency, rapid realization, and cost‐effectiveness. However, pain flare can occur as a side effect that can have a significant impact on a patient's quality of life. With pain flare incidence ranging between 2% and 44%, there are no definitive conclusions about which patients are at greater risk. Aim This study aims to analyze the occurrence of pain flare in relation to age, patient's performance status, primary tumor, histopathology, and bone localization of metastases. Methods Our clinical, prospective, non‐randomized study included 64 patients with non‐complicated, painful bone metastases who underwent palliative, pain‐relieving 8 Gy single‐fraction radiotherapy in a single hospital visit. Response to treatment was patient‐reported via telephone interview using a visual analog scale and assessed based on the international consensus panel of radiation oncologists. Results In the entire group of patients, 17% developed pain flare. No statistically significant difference was observed in pain flare occurrence depending on the patient's age, performance status, the primary origin of the tumor, histopathology, or location of the metastasis (bone) that was irradiated. All but one patient had a good response to treatment after the flare. Conclusion Pain flare can be expected in less than 20% of patients receiving 8 Gy single fraction radiotherapy for painful bone metastases. It is not proven that any of the mentioned clinical parameters influence the occurrence of pain flare. Pain flare does not interfere with response to treatment.