Multi-Institutional Prospective Observational Study of Radiotherapy for Metastatic Bone Tumor

Abstract

<h3>Purpose/Objective(s)</h3> To evaluate patient characteristics and radiotherapy treatments and outcomes in bone metastasis in Japan. <h3>Materials/Methods</h3> Patients for whom radiotherapy for bone metastasis was planned at 26 institutions in Japan between December 2020 and March 2021 were consecutively registered in this prospective, observational study. The number of registrations per facility was limited to 10. Study measures included patient characteristics, pain relief, skeletal-related events (SREs), overall survival, and incidence of radiation-related adverse events. Pain was evaluated by using a numerical rating scale (NRS) from 0 to 10. <h3>Results</h3> Two hundred thirty-two patients were registered; 224 patients and 302 lesions were fully analyzed. Primary sites were lung (36% of patients), breast (15%), and other (49%). ECOG-performance status (PS) was 0 in 23%, 1 in 38%, 2 in 22%, 3 in 13%, and 4 in 4%; 59% of patients had spinal metastases and 84% had painful lesions (at least NRS 2). The biologically effective dose (BED) assuming α/β=10 was <20 Gy (in 27%), 20 to <30 Gy (24%), 30 to <40 Gy (36%), and ≥40 Gy (13%); 9% of patients were treated by stereotactic body radiotherapy (SBRT). For ECOG-PS 3 or 4, 61% of patients were treated with a low BED (<30 Gy); 41% of those with ECOG-PS 0 or 1 were treated with a low BED (<30 Gy). Grade 3 adverse events occurred in 4% and no grade 4 or 5 toxicity was reported. Pain relief was achieved in 52% at 2 months and 58% at 6 months. Use of systemic chemotherapy or hormonal therapy was significantly related to good pain response at 2 months (<i>P</i> = 0.006), but no other factor was associated with pain response. Cumulative incidence of SREs was 6.5% (95% CI 3.1–9.9) at 6 months; no factor was significantly associated with SREs. Among 132 patients with spinal lesions, 10% were classified as Bilsky grade 3; 18% of patients were not ambulatory at baseline; 50% of evaluable patients in this group were able to walk at 2 months. The 6-month overall survival rate was 70.2% (95% CI 64.2–76.9). Good ECOG-PS, ambulatory status at baseline, no other bone metastases, high BED, and SBRT use were significantly related to better overall survival. <h3>Conclusion</h3> We report real-world details of radiotherapy in bone metastasis. BED is not related to pain relief or SRE incidence, but high BED or SBRT were selected for long survivors.