Supine linac treatment versus tomo-therapy in craniospinal irradiation: Planning comparison and dosimetric evaluation

Craniospinal irradiation (CSI) is the standard treatment of primary intracranial tumour with risk of leptomeningeal dissemination. However, supine setup field-in-field technique does not need inter-fractional junction shift. Recently, the studies of CSI with tomo-therapy showed excellent target coverage and tolerable normal organ dose in paediatric patients. The planning comparison and dosimetric difference between conventional radiotherapy and tomo-therapy are presented. Three patients with central nervous system germinoma received supine CSI treatment. Normal tissue complication probability calculation was performed for parotid gland, kidney, lens, small bowel, ovary and testis. Homogenous vertebral body coverage for tomo-therapy compared with conformal radiotherapy was found. The mean dose to each parotid gland decreased by 7.3 and 10 Gy, respectively, with tomo-therapy. The volume of oesophagus and small bowel receiving >10 Gy was significantly lower. The V2, V5, V10 and V20 of the lungs are 81.6, 12.4, 2.3 and 0 % with tomo-therapy. Tomo-therapy showed excellent homogenous dose distribution through the craniospinal axis (PTV) and higher conformity index. (authors)