Portal de Periódicos da CAPES

In Reply

2015; Lippincott Williams & Wilkins; Volume: 77; Issue: 2 Linguagem: Inglês

10.1227/neu.0000000000000797

1524-4040

Evan Thomas, Richard A. Popple, James M. Markert, John B. Fiveash,

Radiopharmaceutical Chemistry and Applications

We thank Dr Fiorentino and colleagues for their interest in our article comparing plan quality and delivery time between RapidArc and gamma knife (GK) for multiple metastasis radiosurgery.1 They raise several important considerations with respect to a comparison of the 2 modalities for multiple metastases radiosurgery. We believe that the authors are correct in their assertion that the importance of low-dose spill in brain metastasis patients is not commensurate with the fervor with which it has been debated in the radiosurgery literature. Although an increasing number of cases of long-term survival in multiple metastases patients are being reported, particularly as newer and more effective therapies become available for extracranial systemic disease, the median overall survival in brain metastasis patients is still short compared with the time at which adverse effects associated with low-dose spill would be expected to manifest. The primary intent of our work was to establish that in a very large proportion of patients with an indication for multiple-target radiosurgery, single-isocenter VMAT is a comparable dosimetric surrogate for GK. We included the low-dose comparison of GK with RapidArc principally for the purpose of establishing the latter's ability to produce comparable dosimetry across all metrics of interest. We would like to take the opportunity to reiterate and underscore for anyone engaged in inverse planning–based treatment that any parameters of interest must be accounted for within the planner's cost function. In conclusion, we agree with the authors that a variety of factors, clinical as well as dosimetric, must be appropriately evaluated before judgment of one technique's superiority over another. We make no such contention here, but do believe that our work establishes that for a substantial majority of multiple brain metastases patients, clinically equivalent dosimetry between VMAT and GK can be achieved. Disclosures Drs Thomas, Popple, and Fiveash have received honoraria from Varian Medical Systems for discussion of the implementation of RapidArc radiosurgery at UAB. The authors have no other personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.