Fractionated Helical Tomotherapy as an alternative to radiosurgery in patients unwilling to undergo additional radiosurgery for recurrent brain metastases

Our clinic routinely treats brain metastases with stereotactic radiosurgery using a 6 megavoltage (MV) linear accelerator, cones, and a surgically attached head frame. Four patients declined repeat radiosurgery for new lesions due to their previous discomfort and a fifth patient could not complete radiosurgery because of uncontrolled nausea. Instead patients were treated with Helical Tomotherapy (HT). This report discusses the spatial dose distribution of HT as measured in a head phantom and the clinical course of these five patients. The planning target volume (PTV) was a 3 mm geometric expansion of the gross tumour volume (GTV). The prescribed dose to the PTV was 27 Gy in five daily fractions with the distribution optimised to deliver 30 Gy to the GTV. Patients were immobilised with a mask and the lesions were targeted by MV computerised tomography, an inherent feature of the system. One patient died six weeks later from systemic disease; the remaining patients survived eight to 16 months. No patient experienced an exacerbation of neurological symptoms following Helical Tomotherapy. These results suggest that fractionated Helical Tomotherapy for brain metastases may be a viable alternative to radiosurgery in patients unable or unwilling to undergo that procedure.