Analysis of long-term outcome of image-guided volumetric modulated arc therapy (VMAT) for primary malignant tumor of the cervical spine.

Objective: Retrospective analysis of the long-term clinical outcome and acute toxicity of the primary malignant tumor of cervical spine receiving CBCT image-guided VMAT.

Methods: Thirty patients with primary malignant tumor of the cervical spine included in our center, from December 2013 to January 2016, 28 patients were retrospectively studied. The prescription dosage 95% PTV volume dose was 44 Gy, 2.0 Gy/fraction, and a total of 22 times. The median PGTV synchronized volume dose was 60 Gy (45-62.1 Gy), median 2.5 Gy (2-2.7 Gy)/fraction. In volumetric modulated, two arc volumetric modulated arc therapy (VMAT) was used, with spinal cord dosage D< 45 Gy. Early response rate and acute toxicities were analyzed.

Result: The follow-up duration was 6-76 months (median 53 months). At the end of follow-up of June 1, 2019, 78.6% (22/28) patients were still alive. 3 and 5-y local control rates were 67.3% and 56.5% while 3 and 5-y OS were both 78.6% in the whole group of patients, respectively. Fourteen patients with chordoma 5-y local control rates and OS were 57.1% and 85.7%, respectively. Nine patients with giant-cell tumor of bone had a 5-y local control rate and OS were 77.8% and 85.7%, respectively. The response rate for moderate pain or above was 80% (8/10). Eleven patients (39.3%) suffered from grade 1 acute skin toxicity. Twenty-four patients (85.7%) had grade 1/2 mucositis. No radiation-induced spinal cord injury was found.

Conclusion: The image-guided VMAT for primary malignant tumor of the cervical spine provided a satisfactory long-term local control rate.