Intensity-modulated stereotactic radiotherapy of paraspinal tumors: a preliminary report

Radioresistant paraspinal tumors may benefit from conformal treatment techniques such as intensity-modulated radiotherapy (IMRT). Local tumor control and long-term palliation for both primary and metastatic tumors may be achieved with IMRT while reducing the risk of spinal cord toxicity associated with conventional radiotherapy techniques. In this article, we report our initial clinical experience in treating 16 paraspinal tumors with IMRT in which the planning target volume was 2 mm or greater from the spinal cord.

IMRT was administered by using a linear accelerator mounted with a multileaf collimator. Two immobilization body frames developed at Memorial Sloan-Kettering Cancer Center were used for patients with and without spinal implants. During a 30-month period, 16 patients underwent IMRT for metastatic and primary tumors. Eleven patients were treated for symptomatic recurrences after undergoing surgery and prior external beam radiotherapy, and one patient was treated after undergoing radiotherapy for a metastatic pancreatic gastrinoma with overlapping ports to the spine. Four patients with primary tumors were treated after primary resection that resulted in positive histological margins. Twelve patients were symptomatic with pain, functional radiculopathy, or both. Tumoral doses were determined on the basis of the relative radiosensitivity of tumors. Patients with metastatic tumors were administered a median tumoral dose of 20 Gy in four to five fractions and a spinal cord maximum dose of 6.0 Gy in addition to the full tolerance dose administered in previous radiation treatments. The primary tumors were delivered a median dose of 70 Gy in 33 to 37 fractions and a spinal cord maximum dose of 16 Gy. The median tumoral volume was 7.8 cm(3).

Of the 15 patients who underwent radiographic follow-up, 13 demonstrated either no interval growth or a reduction in tumor size in a median follow-up period of 12 months (range, 2-23 mo). Two patients, one with a thoracic chondrosarcoma and one with a chordoma, showed tumor progression 1 year after undergoing IMRT. Pain symptoms improved in 11 of 11 patients, and 4 of 4 patients had significant improvement in their functionally significant radiculopathy and/or plexopathy. Pain relief was durable in all patients except the two with tumor progression. No patient showed signs or symptoms of radiation-induced myelopathy, radiculopathy, or plexopathy, including 12 patients with a median follow-up of 18 months.

IMRT was effective for treating pain and improving functional radiculopathy in patients with metastatic and primary tumors. Although long-term tumor control is not established in this study, high-dose tumoral irradiation can be performed without causing radiation myelopathy in more than 1 year of follow-up.