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Defining The Effects of Hypofractionated Radioablation of Renal Cell Carcinoma in a Mouse Model
Anna L. Dowdle, BS, Rupal Bhatt, MD, Elizabeth Genega, MD, Salvatore LaRosa, MS, Irving Kaplan, MD, Xing-Qi Lu, PhD, Nahum Goldberg, MD, Liang Zhang, MD, Xiaoen Wang, MD, Ivan Pedrosa, MD, David Alsop, PhD, Andrew A. Wagner, MD.
Beth Israel Deaconess Medical Center, Boston, MA, USA.

BACKGROUND: Hypofractionated radioablation (HR) of renal tumors has exhibited promising results in a pilot study of non-operative candidates. Despite its use in clinical settings, there is little animal data supporting the treatment of renal cell carcinoma (RCC). We used a nude mouse model to evaluate the effects of the HR against RCC.
METHODS: Nude-beige mice were injected with 786-0 human RCC cell line. Tumors were allowed to grow to approximately 12mm in size prior to treatment. HR was delivered using a Cyberknife® system, with each animal receiving either 15Gy (n=2) or 30Gy (n=4) in a single fraction, while untreated animals served as controls (n=4). Mice were weighed weekly and tumor volume measured every other day for one month or until a predetermined sacrifice time point. Histological evaluation of tumors was completed at 7, 14, 21, and 30-days.
RESULTS: HR resulted in marked reduction in tumor volume after 30Gy and cessation of growth after 15Gy compared to control tumors. Growth curves are displayed in figure 1. Pathological review confirmed viable tumor in all specimens. Tumor necrosis, ranging from 10-25%, was visualized in two tumors, both treated with 30Gy, after 14 and 21 days.
CONCLUSIONS: HR using a single fraction of 30Gy to a mouse RCC model causes reduction in tumor size. Significant amounts of viable tumor remain after 3 weeks. Early signs of cell death support continued investigation of this minimally invasive technology.


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