Fiducial-free CyberKnife stereotactic body radiation therapy (SBRT) for single vertebral body metastases: acceptable local control and normal tissue tolerance with 5 fraction approach

Abstract

This retrospective analysis examines the local control and toxicity of five-fraction fiducial-free CyberKnife stereotactic body radiation therapy (SBRT) for single vertebral body (VB) metastases. All patients had favorable performance status (ECOG 0–1), oligometastatic disease, and no prior spine irradiation. A prescribed dose of 30–35 Gy was delivered in five fractions to the planning target volume (PTV) using the CyberKnife with X-sight spine tracking. Suggested maximum spinal cord and esophagus point doses were 30 and 40 Gy, respectively. A median 30 Gy (IQR, 30–35 Gy) dose was delivered to a median prescription isodose line of 70% (IQR, 65–77%) to 20 patients. At 34 months median follow-up (IQR, 25–40 months) for surviving patients, the 1- and 2-year Kaplan–Meier local control estimates were 80 and 73%, respectively. Two of the five local failures were infield in patients who had received irradiation to the gross tumor volume and three were paravertebral failures just outside the PTV in patients with prior corpectomy. No local failures occurred in patients who completed VB radiation alone. The 1- and 2-year Kaplan–Meier overall survival estimates were 80 and 57%, respectively. Most deaths were attributed to metastatic disease; one death was attributed to local recurrence. The mean maximum point doses were 26.4 Gy (SD, 5.1 Gy) to the spinal cord and 29.1 Gy (SD, 8.9 Gy) to the esophagus. Patients receiving maximum esophagus point doses greater than 35 Gy experienced acute dysphagia (Grade I/II). No spinal cord toxicity was documented. Five-fraction fiducial-free CyberKnife SBRT is an acceptable treatment option for newly diagnosed VB metastases with promising local control rates and minimal toxicity despite the close proximity of such tumors to the spinal cord and esophagus. A prospective study aimed at further enhancing local control by targeting the intact VB and escalating the total dose is planned.

Clinical outcomes of multileaf collimator-based CyberKnife for spine stereotactic body radiation therapy

“…Several SBRT series with CK reported LC rates between 80 and 95%. [22][23][24][25][26][27] We observed a comparable 1 year LC rate of 78%, with no difference between CK-M and CK-F. In addition, treatment of multiple spine levels was correlated with worse LC in accordance with previous study from Balagamwala et al 28 Multilevel disease might inherently be more resistant to treatment and there could be a chance of missing micrometastasis paraspinal region owing to high-conformity of spine SBRT.…”

Stereotactic Body Radiation Therapy: A Review of Applications and Outcomes

“…Radiation to the thoracic cavity may result in any number of side effects including difficulty swallowing, shortness of breath, cough, fever, bone fracture, and radiation pneumonitis. In follow up visits with 36 patients who had undergone chest SBRT for 38 lesions, Turzer et al reported that 34 of the patients had grade 1 pneumonitis, 1 patient had grade 2 pneumonitis and 1 patient had grade 3 pneumonitis [38]. In the same study 16 of the 36 patients presented with temporary chest pain related to the radiation field and all symptoms of inflammation and paid reduced after three months treatment with corticosteroids, NSAIDS, and morphine [38].…”

“…In follow up visits with 36 patients who had undergone chest SBRT for 38 lesions, Turzer et al reported that 34 of the patients had grade 1 pneumonitis, 1 patient had grade 2 pneumonitis and 1 patient had grade 3 pneumonitis [38]. In the same study 16 of the 36 patients presented with temporary chest pain related to the radiation field and all symptoms of inflammation and paid reduced after three months treatment with corticosteroids, NSAIDS, and morphine [38]. Radiation therapy to the abdominal cavity most commonly resulted in diarrhea, nausea, and vomiting and is treated as stated above.…”

Stereotactic Ablative Body Radiotherapy for the Treatment of Spinal Oligometastases

“…One of the few such studies by Gill et al performed was a retrospective review of 20 patients with single vertebral body oligometastases treated with SABR [20]. The most common primary histology was sarcoma, comprising 35% of treated patients.…”