Comparison of pain-relieving effects by number of irradiations, through propensity score matching and the international consensus endpoint.

Background: Palliative radiotherapy for bone metastases utilizes various dose fractionation schedules. The pain-relieving effects of a single fraction (SF) and multiple fractions (MF) are largely debated due to the difficulty in matching patients' backgrounds and in assessing the effectiveness of pain relief. This study aimed to compare the pain-relieving effects of SF and MF palliative radiotherapy for bone metastases using propensity score matching and the international consensus endpoint (ICE).

Materials and methods: Our study included 195 patients irradiated for bone metastasis. The primary endpoint was the pain-relieving effects used by ICE. In addition, the evaluation was performed by using responder (complete response/partial response) and non-responder (pain progression/indeterminate response) categorization. The secondary endpoints were the discharge or transfer rate at one month after irradiation and postirradiation pathological fracture rate. Propensity score matching was used to adjust patient's characteristics and reduce selection bias.

Results: After adapting propensity score matching, the total number of patients was 74. There was no significant difference in the pain-relieving effects between SF and MF (p = 0.184). There were no significant differences in them between SF and MF when using responder and non-responder categorization (p = 0.163). Furthermore, there were no differences in the discharge or transfer rates (p = 0.693) and pathological fracture rates (p = 1.00).

Conclusions: The combination of propensity score matching and ICE revealed no significant difference in the pain-relieving effects between SF and MF for bone metastases, thus, SF has no significant disadvantage compared to MF in pain-relieving effects.