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Gamma knife stereotactic radiosurgery for renal cell carcinoma and melanoma brain metastases—comparison of dose response
Hong-Yiou Lin, Yoichi Watanabe, L. Chinsoo Cho, Jianling Yuan, Matthew A. Hunt, Paul W. Sperduto, Aviva Abosch, Charles R. Watts, and Chung K. Lee

Background: Metastatic melanoma appears to have inferior local control (LC) than renal cell carcinoma (RCC) after stereotactic radiosurgery (SRS) to the brain..

Objective: To retrospectively examine RCC vs. melanoma LC dose response.

Methods: Follow-up data were available for 88 patients (RCC=38; melanoma=50) with 235 tumors (RCC=92; melanoma=143) treated with Gamma Knife SRS between Dec. 2005 to Aug. 2012. LC was compared among RCC vs. melanoma and then at each margin dose (≤18Gy, 20Gy, 22Gy, and 24Gy). Patient survival and toxicity were analyzed. Median follow-up was 9.8 months (RCC) and 5.4 months (melanoma).

Results: Patient characteristics were similar between RCC vs. melanoma with respect to gender, age, KPS, GPA, lesions per patient, and tumor volume. For all margin doses, LC at 6 months was 98.6% (RCC) vs. 79.2% (melanoma). When broken down by margin dose, at ≤18 Gy (P<0.0001) and 20 Gy (P=0.02), RCC had better LC compared to melanoma. At 22 Gy, LC were similar between the two histologies (P=0.19). At 24 Gy, melanoma had better LC than RCC (P=0.02). Tumor volumes were similar between RCC vs. melanoma at each margin dose (P>0.05). Small melanoma tumors (<4ml) exhibited LC dose dependence. Median survival was 16.1 months (RCC) and 9.6 months (melanoma). Toxicity was not significantly different between the two histologies and margin doses.

Conclusion: RCC has significantly better LC than melanoma after SRS. Higher doses could be used for melanoma tumors

Keywords: Radiosurgery; melanoma; renal cell carcinoma; local control

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