Long term outcomes following upfront stereotactic body radiotherapy alone for spinal metastases

Although stereotactic body radiotherapy (SBRT) has radically transformed the treatment paradigm for spinal metastases, long-term outcomes of upfront SBRT in patients with spinal metastases remain underreported.

A cohort of 100 patients (131 treatments) with spinal metastases treated with upfront SBRT alone from 2001 to 2024 was analyzed. Patients with prior lesion-specific surgery or radiotherapy, or less than 6 months of follow-up, were excluded. The median single- and multi-fraction prescription doses were 16-Gy (IQR: 16-18) and 24-Gy (IQR: 24-27), respectively.

The median follow-up was 21 months (IQR: 12-57). The 1- and 2-year local tumor control (LTC) rates were 86% (95%CI: 80-92%) and 81% (95%CI: 73-88%), respectively. On multivariable analysis, tumor volume > 23 cc (HR: 3.20, 95%CI: 1.02-10.1, p = 0.047) was significantly associated with worsened LTC. Patient-reported pain improved or remained stable in 89% and 87% of cases at 6- months and 12-months following SBRT. The median overall survival (OS) was 33 months (IQR: 13-57), with polymetastatic disease (HR: 1.80, 95%CI: 1.05-3.09, p = 0.032) being significantly associated with worsened OS. There were 19 (15%) vertebral compression fractures (VCFs) that developed following SBRT. On multivariable analysis, lumbar lesions (HR: 2.61, 95%CI: 1.01-6.76, p = 0.048) and baseline VCFs (HR: 2.80, 95%CI: 1.10-7.09, p = 0.030) were predictive of VCF development following SBRT.

Upfront SBRT alone provides durable long-term local tumor control and sustained pain relief, with minimal toxicity. These findings support the integration of SBRT as a definitive, minimally invasive treatment option for appropriately selected patients, which may obviate the need for future open surgical intervention.