Stereotactic Radiosurgery with the CyberKnife for Pituitary Adenomas

Abstract

Listen

Translate article

J Korean Neurosurg Soc 45 : 157-163, 2009 10.3340/jkns.2009.45.3.157 To the Editor : It was a pleasure to read another of your outstanding issues. I write regarding the following article, "Stereotactic Radiosurgery with the CyberKnife for Pituitary Adenomas" by Cho et al., J Korean Neurosurg Soc 45 : 157-163, 2009. It is always a pleasure to see additional articles that help to define the role of radiosurgery as a primary or adjuvant management strategy for brain tumors such as pituitary adenomas. Cho et al. have presented their experience in 26 patients with an average follow-up of 2.5 years. The authors note endocrinological improvement (undefined) in nine functioning adenoma patients. While such preliminary data is of interest, the benefit of radiosurgery, like microsurgery, must be defined by normalization of hormonal values. The brief report on hormonal function does not define the methodology used to assess endocrine function, or the actual values which will indicate normalization of the hormonal values (noted in four of nine patients). More importantly, the authors espouse their use of CyberKnife, and note in their discussion section several purported disadvantages of another technology, the Gamma Knife. They note that the Gamma Knife requires "Cobalt reload", a feature which is required in order to do. In contrast, the CyberKnife, a photon delivery system using a Linac, frequently requires extensive quality assurance and technical support, necessitating very high cost maintenance agreements for individual sites. It is true that the gamma knife requires a head frame for interface between the imaging and the treatment delivery. This is, in fact, only one means of assuring accuracy, which is based on the ability to do high resolution anatomic imaging with the frame on (MRI in most cases, in contrast to CyberKnife which most commonly uses poor resolution CT scan imaging), but also because of the 0.1 mm. robotic delivery of the target into the intersection of the photon beams generated by the Cobalt sources. It is for this reason that the instrument accuracy is 0.1 mm. The authors state that the Gamma Knife has major drawbacks "when treating patients with multiple, large, or non-spherical tumors". This is completely inaccurate, as in fact the Gamma Knife, especially using the current generation, Perfexion Unit, was specifically re-designed in order to be able to efficiently and effectively treat multiple, large, and non-spherical tumars (which is in fact the rule for virtually all brain tumor patients). Finally, the authors indicate that the Gamma Knife has no real-time imaging capability implying a deficiency in the system. In fact, the CyberKnife has no real time imaging capability either, but it instead is a "point and shoot" technongy, requiring that imaging be done, followed by verification of accuracy, followed by delivery of radiation. The author's paragraph of description seems disingenuous, and simply parrots marketing information widely disseminated by the Accuray Company. It Would be advantageous for the authors to visit a treatment center currently using a Gamma Knife in order to better understand the differences between CyberKnife radiosurgery and Gamma Knife radiosurgery, and the fallacies in their discussion of the purported disadvantages of the Gamma Knife compared to the CyberKnife. I remain with best personal regards.