Purpose: The role of stereotactic radiosurgery (SRS) alone for patients with gastrointestinal (GI) cancer has yet to be established based on a large patient series. We analyzed post-SRS treatment results and reappraised whether either the GI graded prognostic assessment (GPA) system or modified-recursive partitioning assessment (M-RPA) system was applicable to our 802 SRS-treated patients with GI cancer with brain metastases. Methods and Materials: This was an institutional review board approved retrospective cohort study 2 database comprising 802 patients with GI cancer treated with gamma-knife SRS by 2 experienced neurosurgeons during the 1998 to 2018 period. The Kaplan-Meier method was applied to determine post-SRS survival times, and competing risk analyses were used to estimate cumulative incidences of the secondary endpoints. Results: The median survival time (MST; months) after SRS was 5.7. With the GI GPA system, MSTs were 3.5/6.1/7.7/11.0 in the 4 subgroups, that is, 0 to 1.0/1.5 to 2.0/2.5 to 3.0/3.5 to 4.0, respectively (stratified P < .0001). However, there was no significant MST difference between 2 of the subgroups, GI-GPA 1.5 to 2.0 and 2.5 to 3.0 (P = .073). In contrast, using the M-RPA system, 3 plot lines corresponding to the 3 subgroups showed no overlap and the MST differences between the subgroups with M-RPA were 1 + 2a versus 2b (P < .0001) and 2b versus 2c + 3 (P < .0001). Better Karnofsky performance status score, solitary tumor, well-controlled primary cancer, and the absence of extracerebral metastases were shown by multivariable analysis to be significant predictors of longer survival. The crude and cumulative incidences of neurologic death, neurologic deterioration, local recurrence, salvage whole brain radiation therapy, and SRS-related complications did not differ significantly between the 2 patient groups, with upper and lower GI cancers. Conclusions: This study clearly demonstrated the usefulness of the GI GPA. Patients with GI GPA 1.5 to 2.0 or better or M-RPA 2b or better are considered to be favorable candidates for treatment with SRS alone.
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