Relative thrombocytosis following chemoradiation of patients with glioblastoma to predict survival.

Abstract

e13527 Background: Thrombocytosis is associated with poor survival in several malignancies and is both triggered by and promoting of tumor growth. We hypothesized that an increase in circulating platelets following standard temozolamide (TMZ) CRT and/or adjuvant TMZ would predict for decreased survival in patients with glioblastoma (GBM). Methods: We reviewed data of 122 patients with newly diagnosed, pathological-proven GBM from 2007 to 2016 with documented complete blood counts before the start of CRT, after CRT, before adjuvant TMZ, and after a minimum 2 cycles of adjuvant TMZ. The association between changes in blood count levels and patient survival was analyzed by log-rank test. Multivariate analysis was performed using known prognostic co-variates, including MGMT methylation, patient age, and performance status (PS). Results: The mean change in platelets before and after CRT was -46 k/µl (range -387 to 179 k/µl) and before and after adjuvant TMZ was -25 k/µl (range -408 to 143 k/µl). As a reference, the mean change in lymphocytes was -5.7 k/µl (range -0.7 to 1.3 k/µl) and -0.0 k/µl (range -1.6 to 0.9 k/µl) for CRT and adjuvant TMZ, respectively. Patients were dichotomized based on the relative change in platelets and lymphocytes from baseline (≤30% increase, “low”, n = 101 vs > 30% increase, “high”, n = 12). The median survival of low patients vs. high patients was 30 vs 13 months (p = 0.006). Potential confounders, such as infection or thrombosis, were not associated with the high group. However, no significant survival difference was observed between groups based on platelet changes during adjuvant TMZ. Similarly, changes in lymphocyte counts were not significantly prognostic. In multivariate analysis, extent of resection, MGMT status, PS and the increase in platelets after CRT were significantly associated with survival (HR for platelets 4.0, 95% CI 1.6-10.1). Conclusions: Increased platelet counts after CRT predict for poor survival in patients with GBM. The effect is platelet specific and does not reflect general bone marrow changes, as lymphocyte changes were not significantly prognostic. These results suggest a potential interaction between platelets and tumor aggressiveness.