Top Line: The bone is one of the most common sites of oligometastasis and a common target for metastasis-directed SBRT.
The Study: Multiple trials have evaluated SBRT for bone metastases, and a meta-analysis of SBRT for nonspine bone metastases found excellent long term control and low toxicity. Here’s another phase 2 trial of bone metastasis SBRT that enrolled 67 patients with 79 bone oligometastases (39% spine, 61% nonspine). Just over half of these lesions (53%) were symptomatic, and they had to be mechanically stable and < 5cm. The most common primaries were prostate (32%) and breast (28%). A 5 mm CTV was used, except for standard spine CTVs, and a 2 mm PTV margin was used. The protocol called for a prescription dose of 37.5 Gy in 3 fractions such that 99% of the GTV received 99% of the prescription, mean GTV dose was at or above the prescription, 99% of the CTV received 80% (30 Gy), and 99% of the PTV received 67% (25 Gy). Dmax was limited to 140% of prescription except for targets in the ribs, sternum, scapulae, or long bones where it was limited to 110%. In 22% of patients, the prescription dose was reduced to 30 Gy in 3 fractions due to OAR constraints, which was more common for spine targets. At 1 year, local control was 93.1%. The rate of fracture was 9.9% at 1 year including 13.6% of spine targets and 7.7% of nonspine targets. The rate of treatment related grade 3 toxicity was 4% with no treatment related grade 4 or higher toxicity.
TBL: In this trial using very heterogeneous dosing for spine SBRT, the rate of local control at 1 year was 93% and the risk of fracture was 9.9% which was higher for spine metastases. | Spindler, Int J Radiat Oncol Biol Phys 2025
The Study: Multiple trials have evaluated SBRT for bone metastases, and a meta-analysis of SBRT for nonspine bone metastases found excellent long term control and low toxicity. Here’s another phase 2 trial of bone metastasis SBRT that enrolled 67 patients with 79 bone oligometastases (39% spine, 61% nonspine). Just over half of these lesions (53%) were symptomatic, and they had to be mechanically stable and < 5cm. The most common primaries were prostate (32%) and breast (28%). A 5 mm CTV was used, except for standard spine CTVs, and a 2 mm PTV margin was used. The protocol called for a prescription dose of 37.5 Gy in 3 fractions such that 99% of the GTV received 99% of the prescription, mean GTV dose was at or above the prescription, 99% of the CTV received 80% (30 Gy), and 99% of the PTV received 67% (25 Gy). Dmax was limited to 140% of prescription except for targets in the ribs, sternum, scapulae, or long bones where it was limited to 110%. In 22% of patients, the prescription dose was reduced to 30 Gy in 3 fractions due to OAR constraints, which was more common for spine targets. At 1 year, local control was 93.1%. The rate of fracture was 9.9% at 1 year including 13.6% of spine targets and 7.7% of nonspine targets. The rate of treatment related grade 3 toxicity was 4% with no treatment related grade 4 or higher toxicity.
TBL: In this trial using very heterogeneous dosing for spine SBRT, the rate of local control at 1 year was 93% and the risk of fracture was 9.9% which was higher for spine metastases. | Spindler, Int J Radiat Oncol Biol Phys 2025