Comparison of clinical monocyte count between radiotherapy fractionation schemes for glioblastoma

Committee/Faculty

Presenting Author(s)

LG

Lindsey K. Greenlund, n/a

B.S.
University of Minnesota Medical School
Minneapolis, Minnesota, United States

Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.

Co-Author(s)

RS

Ryan Shanley

M.S.
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
KM

Kellen Mulford

B.A.
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
EN

Elizabeth Neil

M.D.
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
JL

Jessica Lawrence

DVM, DACVIM, DACVR, DECVDI
University of Minnesota
St. Paul, Minnesota, United States

Disclosure: Disclosure information not submitted.
SA

Susan Arnold

DVM, DACVIM
University of Minnesota
St. Paul, Minnesota, United States

Disclosure: Disclosure information not submitted.
MO

Michael Olin

Ph.D
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
GP

G. Elizabeth Pluhar

DVM, Ph.D, DAVCS
University of Minnesota
St. Paul, Minnesota, United States

Disclosure: Disclosure information not submitted.
MH

Matthew Hunt

MD, FRCS, FAANS
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
AV

Andrew Venteicher

M.D., Ph.D.
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
CC

Clark Chen

M.D.
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
CF

Clara Ferreira

Ph.D
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
MR

Margaret Reynolds

M.D.
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
CC

Chinsoo Cho

M.D., MS
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
AS

Aika Shoo

M.D.
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
JY

Jianling Yuan

M.D., Ph.D.
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
KD

Kathryn Dusenbery

M.D.
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
Stephanie Terezakis, MD

M.D.
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
CW

Christopher Wilke

M.D., Ph.D.
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.
LK

Lawrence Kleinberg

M.D.
Johns Hopkins
Baltimore, Maryland, United States

Disclosure: Disclosure information not submitted.
LS

Lindsey Sloan

M.D., Ph.D.
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure: Disclosure information not submitted.

Purpose: Glioblastoma (GBM) is a devastating diagnosis with low survival rates. Increase in tumor-supportive myeloid cells in the peripheral blood has been identified as a prognostic outcome factor. Standard treatment for GBM includes resection, temozolomide (TMZ), and radiotherapy (RT)- often 60 Gy in 30 fractions (fx) with conventionally fractionated RT (CF). Hypofractionated RT (HF) schedules, such as 4005 cGy in 15 fx, may also be employed for older patients (pts) or for those with lower performance status. HF is generally considered to promote anti-tumor immunity more than CF, therefore we sought to determine if there was a difference in peripheral blood monocyte counts between CF and HF. We hypothesized that higher absolute monocyte counts (aMC) would be measured following CF compared to HF.

Methodology: We retrospectively reviewed electronic medical records (EMR) from Fairview pts with the medical diagnosis code for GBM between 7/1/2011 and 6/2/2021. We included pts over the age of 18 who received oncologic care at UMMC. Pts who did not complete their initial RT, had prior RT, or were missing lab data for comparison were excluded. aMc, percent monocytes (%M), and absolute white blood cell count (aWBC) were recorded. Values were analyzed using descriptive summary statistics and t-confidence intervals.

Results: An interim analysis examined 32 pts with available WBC counts (27 CF, 5 HF) and 23 (19 CF, 4 HF) with aMC/%M prior to and following RT. The median pt age was 59 yrs (range: 27-87). Per EMR, 27 (63%) were male, 16 (37%) female, and 0 (0%) non-binary. All pts were planned for concurrent TMZ. For aMC prior to and following RT, the mean difference was -0.1 (95% CI -0.2, 0.1) and -0.2 (95% CI -0.6, 0.1) for CF and HF, respectively. The mean difference for %M was 3.3 (95% CI 0.6, 6.1) for CF and -2.4 (95% CI -5.0, 0.2) for HF. In those who received CF (n=27), the mean difference in aWBC prior to and following RT was -4.2 (95% CI -6.1, -2.3), where in HF (n=5) it was -2.1 (95% CI -6.1, 1.9).

Conclusions: Based on interim findings, we observed different effects for %M between CF and HF. The sample size is too low to be conclusive, but this suggests that more research with larger numbers of HF patients would be useful. This study is limited, as pts are from a single institution and the sample size is small. These are important findings to report, as HF approaches continue to gain favor for their distinct biological properties and delivery convenience.

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