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Safe Treatment of the Maximum Tolerable Brain Metastases with Gamma Knife in Single Patient Clinical Findings

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Y Chen

Y Chen1*, C Li2 , C Yang3 , (1) Monmouth Medical Center, Long Branch, NJ, (2) Chongqing Tumor Hospital, Chongqing, Chongqing, (3) Monmouth Medical Center, Long Branch, NJ


SU-F-T-603 (Sunday, July 31, 2016) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose:Safe treatment of the maximum tolerable brain metastases with GK in single patient–clinical findings

Methods:A patient diagnosed with stage IV NSCLC has received 6 courses of Gamma Knife radiosurgery (GKRS) treatments. The plans were generated with GammaPlan (version 10.1.1), six courses of treatment were administered in 2.5 years. A total of 53 metastases were treated with retreatment foci (n = 5) and planned on newly identified lesions (n = 48). Individual prescription dose varied from 12 Gy to 24 Gy.The homogeneity index (HI) was evaluated as the ratio of maximum dose to prescription dose (HI = (D2% - D98% ) /DRx). The gradient index (GI) was evaluated as the ratio of prescription isodose volume (PIV) at half of the prescription isodose line to PIV (GI = PIV1/2 / PIV). Composite dose of brain from all six courses was generated on Velocity AI (version 3.0.1). All V5, V10, and V12 of brain were estimated.

Results:Mean target volume was 0.39 ± 0.96 cm³ (range from 0.047 to 6.55 cm³). The mean volume of half of prescribed dose was 1.08 ± 2.46 cm³. HI and GI were calculated as 1.37 ± 0.32 and 2.98 ± 0.52, respectively. The patient had no new neurologic symptoms. V₅, V₁₀, and V₁₂ of brain were 820, 118, and 71.94 cc, respectively.All doses were delivered with focused and sharp dose gradients, with superior indexes compared to LINAC based delivery.

Conclusion:With exceptional steep dose gradients, GKRS is ideal to treat multiple metastases in continuous courses. The hot spots were observed in the overlapped area for the given high prescription dose with no side effects.GKRS has advantages of treating multiple brain metastases from NSCLC with low whole brain dose. Our data presented conclusions of excellent local control of large numbers of metastases being treated on GKRS with superior clinical outcome.

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