To investigate the doses given to the kidneys and the small intestines for three radiation therapy techniques [anterior–posterior (APPA) fields, three fields and volumetric-modulated arc therapy (VMAT)] for spinal cord compression (SCC) patients with metastatic disease in the lower thoracic or lumbar spine and to monitor the time spent by clinicians and dose planners.
Radiation therapy is one of the main treatment modalities for SCC. Typical palliative radiation therapy techniques have used APPA fields or a three-field technique.
However, as delivery techniques have evolved dramatically over the past decades, VMAT has gained wide acceptance. VMAT allows for a dose reduction in the organs at risk. Such a dose reduction may result in less toxicity.
The use of the VMAT technique may require more time for contouring and planning compared with the APPA and three-field techniques. Any potential dosimetric benefit of VMAT must not be outweighed by large amounts of extra time spent by clinicians and dose planners.
Materials and methods
For 20 patients treated with radiation therapy for SCC at our hospital, we created a VMAT plan, and the more traditionally used APPA and three-field plans. The mean kidney doses and the volume of bowel, which received 20 Gy, were extracted for each plan. The correlations between parameters for three techniques were determined.
Furthermore, the time required for contouring targets for five patients; and the time required to plan five patients, was recorded.
VMAT lead to the most conformal distributions: the high-dose areas were restricted to the target volume, whereas the healthy tissue, especially the bowel, received a lower dose. In contrast, the APPA plan lead to a larger volume of bowel being irradiated, whereas the three-field technique spared the bowel at the expense of a higher dose to the kidneys.
The average contouring time was 16 minutes, the average planning time was 38 minutes.
Patients treated for SCC in the lower thoracic or lumbar region may benefit from VMAT treatment, as it reduces the dose to the bowel and kidneys compared with APPA or three-field treatments.