To investigate efficacy of three single dose radiation therapy (RT) regimens in the treatment of painful bone metastasis.

Patient self-assessment by using pain chart enabled evaluation of response to treatment that consisted of either one of the three single fractions of 4 Gy (group I; n=109), 6 Gy (group II; n=108), or 8 Gy (group III; n=110).

Patients in groups II and III had higher complete response rate than those in group I, but not significantly, and with no difference between group II and III. However, both patients in group II (73%) and group III (78%) had significantly higher overall response rates when compared to those observed in group I (59%) (I vs II, p=0.025; I vs III, p=0.0019), and with no difference between groups II and III (p=0.39). Patients in group III had shortest time to the occurrence of any pain relief which was significantly better than those observed in group I (Welch's t-test, p=0.012), with no difference between group I and II and group II and III, respectively. There was no difference between the three treatment groups in duration of response and retreatment rate. No effect of histology or metastatic site treated was found. No pathological fractures or spinal cord compressions were observed during the 8 weeks post-RT.

Results of this study seem to confirm that 8 Gy could be considered as probably "lowest" optimal single fraction RT in the treatment of painful bone metastasis, although single fraction RT of 4 Gy should not be easily discarded due to its applicability in specific cases. Since single fraction RT of 6 Gy achieved results not different from that obtained with 8 Gy, further studies are warranted in order to get more informations about "lowest" optimal single fraction RT in the treatment of painful bone metastasis.