Effect of Radiation Treatment Volume Reduction on Lymphopenia in Patients Receiving Chemoradiotherapy for Glioblastoma
Menée auprès de 210 patients atteints d'un glioblastome supratentoriel non métastatique traité entre 2007 et 2016 par radiothérapie en combinaison avec le témozolomide, cette étude évalue la possibilité, sans affecter la survie sans progression et la survie globale, de réduire le volume tissulaire ciblé pour diminuer le risque de lymphopénie aiguë sévère liée au traitement
Objective : Acute severe lymphopenia (ASL) in glioblastoma (GBM) patients after radiation therapy (RT) and concurrent temozolomide (TMZ) predicts for poorer overall survival (OS). This study aims to evaluate whether reduction in radiation treatment volume can reduce risk of ASL. Methods : A total of 210 patients with supratentorial/non-metastatic GBM were treated with RT+TMZ from 2007-2016 and had laboratory data on total lymphocyte counts (TLC). Before 2015, 164 patients were treated with standard-field RT (SFRT), and limited-field RT (LFRT) was implemented thereafter for 46 patients to reduce treatment volume. TLCs were evaluated at baseline, during RT, and at approximately week 12 from initiating RT. ASL was defined as any TLC<500 cells/
μL within 3 months (by week 12) of initiating RT. Multivariate analysis (MVA) for OS was performed with Cox regression and with logistic regression for ASL. Propensity-score matching was performed to adjust for variability between cohorts. ASL, progression-free survival (PFS), and OS were compared using Kaplan-Meier method. Results
:
LFRT patients had higher gross tumor volume (GTV) than SFRT patients yet lower brain dose-volume parameters including volume receiving 25Gy (V25Gy: 41% vs 53%, respectively, P<0.01). TLC at week 12 was significantly higher for LFRT than SFRT (median: 1100 cells/μL vs. 900 cells/μL, respectively, P=0.02). On MVA, ASL was an independent predictor of OS, and brain V25Gy was an independent predictor of ASL. ASL rate at 3 months was 15.5% for LFRT and 33.8% for SFRT (P=0.12). In a propensity-matched comparison of 45 pairs of LFRT and SFRT patients, PFS (median: 5.9 vs 6.2 months, respectively, P=0.58) and OS (median: 16.2 vs 13.9 months, respectively, P=0.69) were not significantly different. Conclusion
:
LFRT is associated with less lymphopenia after RT+TMZ and does not adversely affect PFS or OS. Brain V25Gy is confirmed as an important dosimetric predictor for ASL.