How Does Lymphocyte Depletion Affect Rectal Cancer Radiotherapy Outcomes?

Area of Science:

• Oncology
• Radiation Oncology
• Immunology

Background:

• Pelvic radiotherapy for rectal cancer damages bone marrow, causing radiation-induced lymphopenia (RIL).
• RIL impacts immune function, tumor control, and patient survival.
• The correlation between RIL and treatment outcomes requires further investigation.

Purpose of the Study:

• To analyze lymphocyte variations during pelvic radiotherapy in rectal cancer patients.
• To assess the relationship between RIL, measured by delta lymphocyte count (ΔL), and treatment outcomes.
• To evaluate RIL as a predictor of pathological response, progression-free survival, and treatment toxicity.

Main Methods:

• Retrospective analysis of 97 rectal cancer patients receiving pelvic radiotherapy and chemotherapy.
• Measurement of ΔL as the difference between highest and lowest lymphocyte counts during treatment.
• Kaplan-Meier analysis and multivariate analysis to assess the association between ΔL and outcomes.

Main Results:

• 25.21% of patients experienced grade 3-4 lymphopenia, with a mean ΔL of 350.6 cells.
• Higher radiation doses correlated with greater lymphocyte reduction (Spearman correlation = 0.45, p=0.03).
• Lower ΔL (≤300 cells) was associated with significantly better progression-free survival (HR=0.65, p=0.0013).

Conclusions:

• Delta lymphocyte count (ΔL) is a reliable biomarker for radiation-induced immune suppression in rectal cancer patients.
• ΔL is a significant predictor of pathological response and progression-free survival.
• Immune preservation strategies, including marrow-sparing techniques, are crucial for improving radiotherapy efficacy and reducing toxicity.