2886 - Impact of Post-Treatment Lymphopenia on Clinical Outcomes in Locally Advanced Cervical Cancer

Purpose/Objective(s): Lymphopenia has inferior clinical outcomes in a variety of cancer subtypes. The purpose of this study is to evaluate the association between post-treatment lymphopenia and clinical outcomes in patients with locally advanced cervical cancer (LACC) treated with definitive chemoradiation (CRT).

Materials/Methods: Patients with LACC receiving definitive CRT at a single institution from 2006 – 2024 with available blood count and dosimetry data were retrospectively reviewed. Patient, tumor, and treatment characteristics were collected, including age, stage, lymph node involvement, systemic therapy, radiotherapy dose/fractionation, technique, volume, and clinical outcomes. Volumes receiving x=0.5-50 Gy (VxGy[cc]) were computed from archived planned dose distributions. Post-treatment lymphopenia defined by absolute lymphocyte count (ALC) within 60 days and was graded according to CTCAE v5.0, with severe lymphopenia defined as = Grade 4 (ALC <200). Overall survival (OS), progression free survival (PFS), and local failure (LF) were calculated from start of treatment to date of last follow-up. Continuous variables were compared using the Wilcoxon Rank Sum test when normality assumptions were not met. Categorical variables were analyzed using the Chi-square test or Fisher’s exact test. OS and PFS were calculated using Kaplan-Meier Curve and log-rank test. LF was evaluated using the competing risks cumulative incidence function and tested with Gray's test.

Results: 93 patients met study inclusion criteria with stage IB – IVB disease (13 stage I, 22 stage II, 52 stage III, 6 stage IV) and a median follow up of 2.6 years (range 0.3-10.8 years). Median age was 50.4 years old (range 25.9-77.3 years), and median EBRT was 45.0 Gy (range: 43.2-57.5 Gy). The median OS was 10.0 years, with a 5-year OS, PFS, and LF of 73.0% (95% CI 60.7-87.6%), 57.7% (95% CI 46.2-72.2%), and 12.7% (95% CI 6.4-21.1%), respectively. Grade = 4 post-treatment ALC occurred in 13% of patients. Comparing patients with and without = grade 4 lymphopenia revealed a 5-year OS of 62.3% (95% CI 38.9-99.9%) versus 73.8% (95% CI 59.8-90.9%) (p=0.140), PFS of 41.7% (95% CI 19.2-90.3%) versus 61.5% (95% CI 49.5-76.3%) (p=0.250), and LF of 35.8% (95% CI 9.7-63.6%) versus 9.0% (95% CI 3.6-17.5%) (p=0.010). 10-year OS was 0% versus 64.6% (95% CI 46.2-90.3%), respectively, p=0.023. Treatment factors that correlated with severe post-treatment lymphopenia on univariate analysis included EBRT dose (p=0.002), number of EBRT fractions (p=0.002), total duration of treatment (p=0.011), V50 Gy (p=0.021), and histology (p=0.002).

Conclusion: In this single institution experience of LACC, we found that post-treatment severe lymphopenia correlated with inferior OS and LF. Patients with severe post-treatment lymphopenia may represent a population with less robust immune systems, producing less favorable responses to treatment.