Second single 4 Gy reirradiation for painful bone metastasis.

To investigate the efficacy of the second 4 Gy given as a single fraction radiotherapy (RT) for patients with painful bone metastasis who had already twice received single fraction RT (4, 6, or 8 Gy plus 4 Gy), a total of 25 patients were assessed before and after re-irradiation. The patients included 19 responders and 6 nonresponders to two prior single fraction RT, the latter one being 4 Gy. The overall response rate was 80%, with both complete response (CR) and partial response (PR) being 40%. No difference was found between the previous responders and previous nonresponders regarding both CR (P = 0.70) and overall response rate (P = 0.35). Response duration was longer in the previous responders (P = 0.0041), but the time to pain relief was similar between the two treatment groups. No acute or late high-grade toxicity was observed during this study and no pathological fractures or spinal cord compressions were seen. In this small and highly selected series of patients, the third single fraction RT of 4 Gy was effective and not toxic in the treatment of painful bone metastasis.