Association between unintentional splenic radiation and lymphopenia and high neutrophil/lymphocyte ratio after radiotherapy in patients with esophageal cancer

BACKGROUND: Unintentional irradiation of the spleen may reduce absolute lymphocyte count (ALC), which can affect tumor immunity. Therefore, in the present study, we evaluated spleen dose-volume parameters associated with ALC and neutrophil/lymphocyte ratio (NLR) in patients with esophageal cancer. METHODS: This retrospective study evaluated patients who were diagnosed with stage I–IV esophageal cancer and who received radiotherapy at Nihon University Itabashi Hospital between January 2015 and March 2020. Spleen V5, V10, V20, and V30 and mean spleen dose, which are dose-volume histogram parameters correlated with ALC and NLR, were analyzed. RESULTS: In total, 89 esophageal cancer patients with a median age of 72 years (range, 51–92 years) were included in this research. Results showed that spleen V5, V10, and V20 and mean splenic dose were significantly correlated with a low ALC. Meanwhile, a significant association was observed between spleen V5 and V10 and a high NLR (P<0.05). In the linear regression analysis, spleen V5 and V10 were remarkably associated with a low ALC (P=0.006 and 0.008). Further, a correlation was noted between spleen V5 and a high NLR (P=0.019). Spleen V5 and V10 were remarkably associated with greater than grade 3 lymphopenia (P=0.024 and P=0.031). CONCLUSIONS: A correlation was observed between the irradiated volume of the spleen and ALC and NLR in patients with esophageal cancer. Furthermore, the spleen should be regarded as a high-risk organ, and the use of techniques in reducing spleen V5, V10 for the preservation of tumor immunity may be beneficial.