The relationship between splenic dose and radiation-induced lymphopenia

Area of Science:

• Radiation Oncology
• Medical Physics
• Immunology

Background:

• Lymphocytes are crucial for anti-tumor immunity and sensitive to radiation.
• Radiation-induced lymphopenia is linked to adverse outcomes in cancer patients.
• The spleen, a major lymphoid organ, is not officially recognized as an organ at risk in radiation therapy protocols.

Purpose of the Study:

• To investigate the association between spleen irradiation and radiation-induced lymphopenia in gastric cancer patients.
• To establish evidence-based spleen radiation dosage limits.
• To identify predictors of lymphopenia and their impact on survival outcomes.

Main Methods:

• Retrospective analysis of 96 locally advanced gastric cancer patients undergoing postoperative chemoradiotherapy (CRT).
• Collection and analysis of complete blood counts (CBC) before, during, and after CRT.
• Development of a predictive model for minimum absolute lymphocyte count (Min ALC) and investigation of spleen dosimetric variables (e.g., spleen V5) and their correlation with Min ALC.

Main Results:

• Spleen V5 (dose delivered to 5% of spleen volume) and primary tumor location were significant predictors of Min ALC.
• Higher spleen radiation doses were associated with an increased risk of severe lymphopenia.
• Changes in absolute lymphocyte count (ΔALC) during therapy independently predicted overall survival (OS) and disease-free survival (DFS).

Conclusions:

• Spleen irradiation dose is a critical factor in radiation-induced lymphopenia.
• Restricting spleen radiation dose (e.g., spleen V5) is recommended in clinical practice.
• ΔALC serves as a valuable prognostic indicator for patients receiving adjuvant radiotherapy for gastric cancer.