Effect of Radiation Treatment Volume Reduction on Lymphopenia in Patients Receiving Chemoradiotherapy for Glioblastoma

Publication date: Available online 1 February 2018
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Soumon Rudra, Caressa Hui, Yuan Rao, Pamela Samson, Alexander Lin, Xiao Chang, Christina Tsien, Sandra Fergus, Dan Mullen, Deshan Yang, Dinesh Thotala, Dennis Hallahan, Jian Li Campian, Jiayi Huang
ObjectiveAcute 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.MethodsA 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.ResultsLFRT 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.ConclusionLFRT 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.



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