Stereotactic radiotherapy of central nervous system and head and neck lesions, using a conformal intensity-modulated radiotherapy system (Peacock (TM) system)

The objective of this article is to evaluate single-fraction or fractionate d stereotactic radiotherapy of central nervous system (CNS) and head and ne ck lesions using intensity-modulated radiotherapy (IMRT) with a commerciall y available system (Peacock(TM), Nomos Corporation, Sewickley, PA). This sy stem allows tomotherapeutic delivery of intensity-modulated radiation, that is, the slice-by-slice treatment of the volume of interest with an intensi ty-modulated beam, making the delivery of highly conformal radiation to the target possible in both single or multiple fractions mode. During an 18-mo nth period, 43 (21 males and 22 females) patients were treated, using a rem ovable cranial screw-fixation device. Ages ranged from 10 to 77 years (mean , 52.2; median, 53.5). Intra- and extra-axial lesions, including head and n eck malignancies and spine metastases, were treated. Clinical target volume ranged from 0.77 to 195 cm(3) (mean, 47.8; median, 29.90). The dose distri bution was normalized to the maximum and was prescribed, in most cases, at the 80% or 90% isodose line (range, 65 to 96%; median, 85%; mean, 83.4%) an d ranged from 14 to 80 Gy (mean, 48; median, 50). The number of fractions r anged from 1 to 40 (mean, 23; median, 25). In all but one patient, 90% of t he prescription isodose line covered 100% of the clinical target volume. Th e heterogeneity index (the ratio between the maximum radiation dose and the prescribed dose) ranged between 1.0 and 1.50, whereas the conformity index (the ratio between the volume encompassed by the prescription isodose line and the clinical target volume) ranged between 1.0 and 4.5. There were no complications related to the radiation treatment. With a median followup of 6 months, more than 70% of our patients showed decreased lesion size. Ster eotactic IMRT of CNS and head and neck lesions can be delivered safely and accurately. The Peacock system delivers stereotactic radiation in single or multiple fractions and has no volume limitations. It has been used to trea t intracranial, head and neck, and spinal lesions. The option of fractionat ion, the lack of volume constraint, and the capability of treating intracra nial, head and neck, and spinal pathology make stereotactic IMRT a valuable adjunct to established stereotactic radiotherapy systems delivering conver gent-beam irradiation using the Linac or Gamma Knife. In a clinical setting that offers Linac, Gamma Knife radiosurgery, and conformal stereotactic ra diotherapy, the latter may have advantages for treating large (> 25-cm(3)) and irregular lesions, especially when fractionation is considered useful.