• Gamma Knife Radiosurgery for Metastases ≥ 2cm: Outcomes and Prognostic Factors

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    Mahmoud Aly Abbassy MD; Alireza M. Mohammadi MD; Symeon Missios MD; Samuel T. Chao MD; John H. Suh MD; Gene H. Barnett MD; Michael A. Vogelbaum MD, PhD; Biji Bahuleyan MBBS, MCh; Gennady Neyman; Lilyana Angelov MD

    Study Design:

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2015 Annual Meeting

    Introduction: Gamma Knife radiosurgery(GK-RS) has been recognized as an effective modality for treatment of brain metastases(BM). We are reporting our series of patients with large brain metastases, >2 cm in diameter, who received GK-RS according to RTOG90-05 dosing as a part of their treatment, focusing on factors affecting the progression-free survival(PFS), overall survival(OS) and radiation necrosis(RN).

    Methods: 273 patients with >2 cm BM were treated with GK-RS at our institution (2000-2012) and their data are maintained in as IRB-approved database. Multivariate analysis was used to determine the prognostic factors affecting the PFS, OS and RN.

    Results: 273 patients with 303 BM >2 cm were included. Median age was 61y(19-92). Primary cancers were non-small cell lung cancer 116 (42%), renal 36 (13%), breast 36 (13%), colon 20 (7%), small cell lung cancer 17 (6%) and others 48 (18%). Median OS was 9 mo. The estimated local control at 1 year in patients who had at least 1 post GK-RS MRI was 83±3%(based on uncensored patients) with median PFS of 7.1 mo. Factors that were significantly decreased the PFS included: presence of extracranial(ECM) metastases, Karnofsky performance score(KPS) =70 and history of whole brain radiotherapy(p-value= <0.001, 0.001 and 0.02 respectively). Factors adversely affecting the OS included: presence of ECM, KPS=70 and =6 mo interval between the diagnosis of the primary and the appearance of BM (p-values <0.0001, 0.003, 0.05, respectively). Maximum diameter of =3cm was the only factor adversely affecting RN risk (p-value=0.05). Type of primary and history of surgical excision did not affect any of the studied outcomes.

    Conclusions: Using the prescription doses suggested by the RTOG 90-05; factors that adversely affected the PFS included ECM, KPS=70 and in addition to those factors, =6 mo as an interval between the diagnosis of the primary and the appearance of BM was recognized as a poor prognostic factor.

    Patient Care: Patients need to know and understand the prognostic factors regarding their GK treatment. The local control reseults emphesize the role of the GK as tool in the treatment of the large brain metastasis.

    Learning Objectives: - Various prognostic factors that are governing the outcome in patients with brain metastasis treated by Gamma knife Radiosurgery.


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