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Pre- and Mid-Treatment Predictors of Lymphocyte Counts Post-Proton and Photon Radiotherapy in Patient with Low Grade Gliomas

C Zhu1*, R Mohan2 , S McGovern3 , J Dinh4 , W Cao5 , A Liu6 , G Jun7 , X Bai8 , D Grosshans9 , (1) UT MD Anderson Cancer Center, Houston, TX, (2) UT MD Anderson Cancer Center, Houston, TX, (3) UT MD Anderson Cancer Center,Houston,TX,(4) Baylor College of Medicine,Houston,TX ,(5) UT MD Anderson Cancer Center, Houston, TX, (6)UT MD Anderson Cancer Center, Houston, TX, (7) UT Health Science Center at Houston, Houston,TX ,(8) University of Houston, Houston,TX ,(9)UT MD Anderson Cancer Center, Houston, TX


(Tuesday, 7/16/2019) 3:45 PM - 4:15 PM

Room: Exhibit Hall | Forum 2

Purpose: To explore the effects of pre-treatment and mid-treatment factors on the absolute lymphocyte counts (ALC, K/μL) after proton and photon radiotherapy of glioma patients.

Methods: The study cohort consisted of 65 photon and 34 proton patients. The study’s primary endpoint is the ALC one month post radiotherapy (RT), the time point when the most significant gap in ALC was observed between the two modalities. The primary predictors included RT modality, Whole Brain Mean Dose (WBMD cGy) and one of preselected Whole Brain (WB) V2, V5 and V10 which were negatively correlated with 1-month post RT ALC (p<0.05). Linear regression model was implemented to predict post RT ALC at one month based on the primary predictors and a set of baseline clinical profiles selected by elastic-net regression using 10-fold cross validation.

Results: Two treatment cohorts had similar baseline ALC levels (photons 1.8, protons 1.71). Average ALC for photon patients declined to 1.31 one month post RT and maintained at a relatively constant level until one year. In contrast, the proton group had a slightly elevated average ALC level until a drop to 1.17 during 3-6 months post RT. A moderate recovery (1.44) was observed by the end of 12 months. The final model included radiation modality, baseline ALC, gender, WB V10, Body Mass Index (BMI) and WBMD. Baseline ALC and BMI demonstrated protective effect on the primary endpoint (coefficient: 0.39, p<0.001; 0.025, p=0.038). WB V10 was negatively associated with the primary endpoint, though not significant statistically (coefficient: -0.0279, p=0.062).

Conclusion: Post RT ALC levels at 1-month were positively correlated with protons, baseline ALC and BMI. There was a negative association between WB V10 and post RT ALC though it was not statistically significant; however, further research is warranted to study this effect for a larger cohort.


Radiation Therapy, Dose Volume Histograms


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