Change in platelet levels during radiotherapy with concurrent and adjuvant temozolomide for the treatment of glioblastoma: a novel prognostic factor for survival.

Background: Radiotherapy plus concomitant and adjuvant temozolomide (RCAT) is now standard treatment for grade IV glioblastoma (GBM). We report the results from our 7 years experience of using RCAT, and the potential role of a change in platelet count as a prognostic factor.
Methods: We identified all patients with biopsy-proven GBM who received RCAT at the Royal Free Hospital between 2002 and 2009. We extracted data on demographic, tumour and treatment variables and overall survival and conducted univariate analyses on the association of the baseline factors with survival, and included those that were significant in a multivariate model. We then conducted exploratory analyses on the impact of changes in haematological parameters and overall survival.
Results: A total of eighty-four patients were included in the final analysis. Median overall survival in our study was 17.6 months. Overall survival rate at 1 year and 2 years were 70 and 36 %, respectively. Platelet counts were seen to fall when measured from baseline to beginning of week 6. A decrease in platelet count from baseline to week 6 was associated with longer survival (p = 0.006), and this remains significant when adjusted for known prognostic factors.
Conclusion: Our study shows the survival benefit seen in the phase III trial is reproducible in clinical practice. In addition, decreased platelet count during concurrent radiotherapy and temozolomide appears to correlate with prolonged survival, a finding that warrants further investigation.