ACT-05 PREDICTIVE FACTORS RELATING TO OUTCOME AFTER RESECTION OF LOW-GRADE GLIOMAS WITHOUT CHEMOTHERAPY OR RADIOTHERAPY

BACKGROUND: There are several treatment options, including observation, after surgical removal of low-grade gliomas (LGG). If postoperative chemotherapy and/or radiotherapy are not provided, resection-alone approach will probably be alternative to a natural course of LGG under observation. The objective of this study was evaluation of prognostic factors associated with overall survival (OS) of patients with LGG treated with surgery alone. METHODS: A consecutive series of 236 adult patients who underwent surgery for LGG without adjuvant therapy was analyzed retrospectively. In 193 cases (82%) histopathology of the tumor was re-classified based on evaluation of IDH1 mutational status and 1p/19q co-deletion according to criteria of WHO classification 2016. Cox proportional hazards model was used for statistical analysis. RESULTS: Median extent of resection (EOR) was 95% (range, 1–100%) and in 210 cases (89%) EOR was >=90%. During postoperative follow-up tumor progression was noted in 106 patients, and 30 patients died of disease. Overall, 10-year OS rate was 82.0%. There was statistically significant difference (P <0.001) in OS among molecularly re-classified tumors, with 10-year OS rates of 90%, 79%, and 75% in cases of OD, DA IDH1-mutant, and DA IDH1-wild, respectively. In patients with EOR >=90% 10-year OS rate was 75%. Multivariate analysis revealed that only EOR >=90% (RR, 0.23; 95% CI, 0.09–0.66; P<0.007) and presence of 1p/19q co-deletion (RR, 0.41; 95% CI, 0.16–0.97; P = 0.042) are independently associated with OS. In patients with EOR >=90% such factors as type of disease manifestation, time interval between onset of symptoms and surgery, and molecular subtype of the tumor did not show significant associations with OS. CONCLUSION: Survival outcome in patients with LGG who underwent surgical resection alone may be predicted by EOR and presence of 1p/19q co-deletion. In cases with EOR >=90% molecular subtype of the neoplasm does not impact OS.