Abstract
Advancement in systemic therapy has increased the importance of local control (LC) of bone metastatic sites treated with radiotherapy in intermediate-term survivors (surviving ≥1 year). To establish individualized radiotherapy for bone metastases, factors affecting LC of bone metastases treated with traditional fractionated moderate dose palliative radiotherapy (FMRT) in intermediate-term survivors were evaluated. Between January 2010 and December 2019, 317 lesions in 240 patients treated with FMRT for bone metastases surviving for at least 1 year and followed-up with CT for at least 6 months were reviewed retrospectively. The median survival and radiographic follow-up times were 24 months (range, 12-123 months) and 20 months (range, 1-119 months), respectively. The median FMRT dose [biologically effective dose (BED)10] was 39.0 Gy (range, 28.0-71.7 Gy). Multivariate analysis revealed that age (≥70 years), non-vertebral bone metastasis, bone metastasis from moderate and unfavorable primary tumor sites (esophageal, colorectal, hepatobiliary/pancreatic, kidney/ureter and sarcoma/melanoma cancers), and no administration of post-FMRT bone-modifying agents (BMAs) were unfavorable factors for LC of bone metastasis. The 2-year LC rates for FMRT doses (BED10) ≤39.0 Gy and >39.0 Gy were 90 and 87%, respectively. The 2-year LC rates of patients administered and not administered post-FMRT antineoplastic agents (ATs) were 91 and 78%, respectively. The sites of bone metastasis and primary tumors, and post-FMRT BMAs were factors associated with LC of bone metastasis in long-term survivors. However, a FMRT dose (BED10) ≥39.0 Gy and post-FMRT ATs were not significant factors.