City of Hope Comprehensive Cancer Center Duarte, CA
A. Kassardjian1, Q. Feng1, Z. Huang2, A. Tam1, N. J. Eustace1, R. S. Davis3, C. J. Ladbury1, J. R. Liu1, and Y. R. Li1; 1Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA, 2City of Hope National Medical Center, Duarte, CA, 3City of Hope Comprehensive Cancer Center, Duarte, CA
Purpose/Objective(s): Leukopenia is a common hematologic toxicity observed after radiation therapy (RT). These conditions are characterized by reduced levels of absolute lymphocyte count (ALC) and absolute neutrophil count (ANC), which may impact patients’ overall health, immune function, and risk of comorbid infections. This study examines the impact of pelvic RT on ALC and ANC and incidence of respiratory viral infections. Materials/
Methods: We examined prostate cancer patients at a single comprehensive cancer center treated with curative-intent pelvic RT between 2010 and 2023. Patients were identified based on whether they received prostate and pelvic nodal RT of at least 25 fractions. Laboratory values including ALC and ANC were collected. Time to leukopenia was defined from RT start date up to 1 year after RT end date. Lymphopenia and neutropenia were defined using laboratory standard reference range cutoffs of ALC less than 0.70 thousand cells (K) per microliter (µL) and ANC less than 1.40 K/µL, respectively. Statistical analysis and comparison between groups were performed using Kaplan-Meier competing risk survival analyses. Results: We identified 322 patients who received pelvic RT for prostate cancer between 2010 and 2023. The median age was 73.5 years [range 54.0-93.1 years], and most patients were non-Hispanic white (62.1%). The median duration of RT was 55 calendar days. While 150 patients (46.6%) developed lymphopenia, only 14 patients (4.3%) developed neutropenia within 1 year of completing RT. Moreover, 4 patients (1.2%) developed clinically significant neutropenia (ANC<1.0), whereby RT is typically held. The median ALC nadir was 0.50 K/µL [range 0.17-0.66 K/µL], and the median time to ALC nadir was 74.5 days [range 17-425 days] after starting RT. The median ANC nadir was 1.06 K/µL [range 0.7-1.0 K/µL], and the median time to ANC nadir was 147 days [range 26-413 days] after starting RT. 90 patients (60.0%) with lymphopenia recovered to normal laboratory values within 1 year of completing RT, and median duration of recovery was 91.5 days [range 5-364 days]. Additionally, 8 patients (57.1%) with neutropenia recovered to normal laboratory values within 1 year, and median duration of recovery was 66 days [range 4-167 days]. Finally, there were 16 patients (10.7%) with lymphopenia who developed respiratory virus and/or COVID-19 infection within 1 year of completing pelvic RT. Conclusion: Pelvic RT results in significant and sustained leukopenia in men with prostate cancer. Consistent with prior studies, we showed that more patients developed lymphopenia versus neutropenia. Most patients recovered to standard reference values within 3 months. Additional studies are required to further identify predictors of leukopenia, such as dosimetric considerations of bone marrow, and whether patients with lymphopenia are at increased risk of respiratory infections. These results may guide clinical intervention of patients at highest risk for toxicity.
