3643 - Quantification of Temporal Cytopenic Changes during Concurrent Head and Neck Chemoradiation

S. Ebrahimi¹, M. Weng², E. Y. Liu¹, P. T. Courtney¹, J. E. Juarez Casillas³, M. L. Steinberg¹, D. J. Wong⁴, W. Chai-Ho⁴, R. K. Chin¹, and R. R. Savjani¹; ¹Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA, ²UCLA David Geffen School of Medicine, Los Angeles, CA, ³Department of Radiation Oncology, University of California Los Angeles, Los Angeles, CA, ⁴David Geffen School of Medicine at UCLA, Dept of Medicine, Division of Hematology/Oncology, Los Angeles, CA

Purpose/Objective(s): Among patients receiving RT for non-hematological malignancies, grade 3+ neutropenia, lymphocytopenia, anemia, and thrombocytopenia have been reported in 9.7%, 44.6%, 8.3%, and 3.1% of cases, respectively. Concurrent head and neck chemoradiation (CCRT) can significantly impact hematological balance - the blood flow through the carotid arteries is 3.6-10 L/min and the region contains around 400 lymph nodes. Our study quantifies the temporal changes in blood cell counts during CCRT. Materials/

Methods: EHR data at our institution was queried for patients diagnosed with head and neck malignancies. Custom Python scripts were used to identify patients who had at least four weeks of radiation. Complete blood count (CBC) data were collected from up to two weeks prior to radiation start to two weeks after radiation completion. CBC data for each patient were then collated into a Pandas data frame and exported and analyzed with RStudio.
Results: Our study included 814 patients (34% female, median age 64 years, 95% CI 63-65) undergoing chemoradiation for head and neck cancers from March 2013 to March 2023. Racial composition was 51% Caucasian, 31% unknown/other, 10% Asian, 3% Black, 2% Middle Eastern, 2% multiple races and <1% AI/AN or NH/PI. Staging data, available for 50-61% of the cohort, revealed 22% had advanced T4 disease, 69% had nodal involvement, and 7% presented with metastatic disease. CBCs were tracked from two weeks pre-treatment to 95 days after, with patients having a median of 6 lab draws (IQR 2-8). Initial median values for key CBC components were as follows: white blood cell (WBC) count at 6.49 (95% CI 6.32-6.7), hemoglobin at 12.1 (11.9-12.3), absolute neutrophil count (ANC) at 4.29 (4.07-4.51), absolute lymphocyte count (ALC) at 1.36 (1.28-1.43), and platelet count at 231 (225-235). Notably, 90% of the data was gathered within 50 days of treatment start and during this time there was a significant daily decrease in WBC (correlation coefficient ? = -0.008 ± 5.2 x 10^-4), hemoglobin (? = -0.002 ± 1.3 x 10^-4), ANC (? = -0.008 ± 5.4 x 10^-4), and ALC (? = -0.013 ± 8.5 x 10^-4), with p-values < 2.2 × 10^-16 and R² values ranging from 0.78 to 0.86. There was no significant difference in the rate of lymphocyte decline when comparing by age (=64 vs. older) or sex. The decline in platelet counts followed a U-shaped trajectory, with a significant decline during the first 25 days (? = -0.005 ± 5.4 x 10^-4, p = 1.4 x 10^-11, R²= 0.70), followed by a gradual increase thereafter (? = 0.009 ± 0.003, p = 0.01, R²= 0.26).
Conclusion: Our study profiles the hematologic changes in 814 patients undergoing CCRT for head and neck cancer, revealing a notable decline, 0.8% and 1.3% per day in WBC/ANC and ALC respectively, alongside a U-shaped trajectory in platelet counts. These findings underscore the critical impact of H&N chemoradiation on hematologic parameters and the potential need for tailored management strategies in this patient population.