Phase 2 Clinical Trial of Stereotactic Body Radiation Therapy for Painful Nonspine Bone Metastases.

Purpose: The present multicenter, single-arm, phase 2 study aimed to prospectively evaluate the palliative efficacy of stereotactic body radiation therapy (SBRT) in patients with painful nonspine bone metastases.

Methods And Materials: Patients with painful (≥2 points on a 0-to-10 scale) nonspine bone metastases from a solid tumor were enrolled. The prescribed dose was 35 Gy in 5 fractions. The primary endpoint was overall pain response rate (complete response [CR] and partial response [PR]) as measured per the International Consensus on Palliative Radiotherapy Endpoints guideline 6 months after SBRT.

Results: Forty-one osseous lesions in 38 patients were registered between June 2018 and June 2019. All lesions satisfied the inclusion criteria, and the patients completed the protocol treatment. Patients most commonly had lung cancer (22%), followed by prostate cancer, uterus cancer, and renal cell carcinoma (15%, 15%, and 12%, respectively). Bone metastases were most commonly located in coxal bones (56%). The median duration of follow-up after registration was 8 months (range, 1-19 months). Among evaluable lesions at 3 and 6 months after SBRT, the 3- and 6-month pain response rates were 78% and 75%, respectively. The local control rate at 6 months was 92%. Seven patients (17%) experienced bone fracture after irradiation, and 3 patients (7%) experienced grade 2 limb edema. One patient had regrowth of coxal bone metastases, and the tumor penetrated the sigmoid colon. Soft tissue abscess around the tumor and osteonecrosis of coxal bones were confirmed. The patient died of infection 4 months after SBRT and was determined to be a possible treatment-related death.

Conclusions: This prospective clinical trial showed that SBRT for nonspine bone metastases was effective in terms of pain palliation. These findings warrant a larger randomized controlled trial to compare SBRT with conventional radiation therapy. Additionally, operation history should be considered as a risk factor for edema.