Approaches to radiotherapy in metastatic spinal cord compression.

Metastatic spinal cord compression is caused by the progression of metastatic lesions within the vicinity of the spinal cord. The consequences are very severe with loss of neurological function and severe pain. The standard treatment is surgical intervention followed by radiotherapy or radiotherapy alone. However, the majority of patients are treated with radiotherapy only due to contraindications to surgery and technical inoperability. Stereotactic body radiotherapy is a technology to deliver higher radiation dose to the radiotherapy target with the use of spatial coordinates. This modality has shown positive results in treating lesions in brain and lungs. Hence, it could prove beneficial in metastatic spinal cord compression. We designed and planned a trial to investigate this method in patients with metastatic spinal cord compression. The method was usable but the trial was stopped prematurely due to low accrual that made comparison with surgery impossible. Low accrual is a known problem for trials evaluating new approaches in radiotherapy. Target definition in radiotherapy of metastatic spinal cord compression is defined by patient history, examination and imaging. Functional imaging could provide information to guide target definition with the sparring of normal tissue e.g. spinal cord and hematopoietic tissue of the bone marrow. In future trials this may be used for dose escalation of spinal metastases. The trial showed that PET/MRI was feasible in this group of patients but did not change the radiotherapy target in the included patients. Neurological outcome is similar irrespective of course length and therefore single fraction radiotherapy is recommended for the majority of patients. In-field recurrence is a risk factor of both short and long fractionation schemes and re-irradiation have the potential risk of radiation-induced myelopathy. In a retrospective study of re-irradiation, we investigated the incidence of radiation-induced myelopathy. In our study population, we found a higher number of patients experiencing vertebral fractures than the number of patient developing myelopathy. Patients with diabetes had an increased risk of toxicity compared to the remaining patients. Stereotactic body radiotherapy is effective in treating metastatic spinal cord compression but the efficacy cannot be determined due low accrual. The use of PET/MRI did not spare normal tissue in radiotherapy planning of spinal metastases. The incidence of toxicity after re-irradiation of the spine and spinal cord was low. For patients with in-field recurrence, re-irradiation is safe and has a low incidence of toxicity.