Upfront Gamma Knife radiosurgery alone for brain metastases: the prognostic value of DS-GPA and RPA.

Anna Likhacheva1, Chelsea Pinnix2, Neil Parikh3, Pamela Allen2, Erik Sulman2, Anita Mahajan2, Daniel Cahill4, Almon Shiu5, Paul Brown2, Eric L. Chang2

1Houston, United States 2Department of Radiation Oncology, UT MDACC, Houston, Texas USA 3Baylor School of Medicine, Houston, Texas USA 4Department of Neurosurgery, UT MDACC, Houston, Texas USA 5Department of Radiation Physics, UT MDACC, Houston, Texas USA

Keywords: grading system, brain metastasis, gamma knife, radiosurgery, outcome

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     Grading systems are valuable for the study of brain metastases outcomes.
     We sought to validate Diagnosis Specific Graded Prognostic Assessment (DS-GPA), a new prognostic index that takes into account histology of the primary, and RTOG Recursive Partitioning Analysis (RPA) system using a single institution database of patients treated with initial radiosurgery (SRS) alone for brain metastases (BM).
     224 patients were treated using Leksell Gamma Knife and 28 using LINAC-based delivery.
     We retrospectively identified adult patients who underwent SRS at our institution for upfront treatment of BM between 2009 and 2010 but excluded those who underwent previous craniotomy and/or WBRT (n=252).  The population was grouped into DS-GPA 0-0.5 (n=19), 1 (n=46), 1.5 (n=52), 2 (n=67), and ?2.5 (n=63). The same patients were also grouped by RPA class: 1 (n=24), 2 (n=212), and 3 (n=10). Most common histologies were non-small cell lung cancer (34%), melanoma (30%), and breast carcinoma (16%). Median number was 2 (range: 1-13) and median total tumor volume was 0.9 cm3 (range 0.3-22.9 cm3). Median dose was 20 Gy (range 15-25 Gy). SRS was used as sole management (62% of patients), or in combination with salvage treatment with SRS (22%), WBRT (13%) or neurosurgery (3%). Median follow-up was 7.5 months.
     Median overall survival (OS) was 11.1 months. Median survival times were 4.0 months for DS-GPA 0–0.5, 5.6 months for DS-GPA 1, 8.1 months for DS-GPA 1.5, 21.5 months for DS-GPA 2, and 30 months for DS-GPA?2.5 (p<0.0001). In the RPA groups, median OS was not reached for class 1, was 10.8 months for class 2, and 2.8 months for class 3 (p<0.0001). Neither RPA, nor DS-GPA was prognostic for local control or new lesion-free survival. Multivariate analysis revealed that age > 60, KPS?80, and uncontrolled primary disease were significant adverse prognostic factors for OS.
     This was a retrospective evaluation.
     When applied to patients treated with upfront SRS for newly diagnosed BM, RPA and DS-GPA indices prove to be valid, splitting patients into prognostically different groups. Application of DS-GPA to patients treated with SRS provides additional prognostic refinement over that provided by the RPA. 
     DS-GPA may allow for selection of treatment modality based on predicted patient outcome.


Project Roles:

A. Likhacheva (), C. Pinnix (), N. Parikh (), P. Allen (), E. Sulman (), A. Mahajan (), D. Cahill (), A. Shiu (), P. Brown (), E. Chang ()