Changes in tumor-infiltrating lymphocytes and inflammatory blood factors during CRT in rectal cancer.

Background: Multidisciplinary treatments for advanced rectal cancer are diverse. Neoadjuvant chemoradiation therapy (nCRT) is a total neoadjuvant therapy treatment option. Some studies have reported that tumor-infiltrating lymphocytes (TILs) and inflammatory blood factors [(neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), and systemic immune inflammatory index (SII)] are predictors of nCRT efficacy. However, the relationship between changes in TILs and inflammatory blood factors during nCRT and the resulting tumor regression grade (TRG) remains unclear. In this study, we investigated whether changes in TILs and inflammatory blood factors during nCRT were related to TRG.

Methods: We retrospectively studied 196 patients with rectal cancer who underwent curative resection after nCRT for advanced rectal cancer. Immunohistochemical staining of lymphocyte surface markers, including CD3, CD4, and CD8, was performed on biopsy specimens before and during nCRT. Inflammatory blood factors were assessed using blood samples collected before treatment and seven days after the initiation of nCRT.

Results: Changes in CD4 levels were related to TRG. NLR and SII during nCRT were associated with TRG. TRG tended to be better in patients with values below the cut-off. The NLR during nCRT and changes in NLR, PLR, and SII were associated with the tumor shrinkage rate. Changes in PLR were related to TRG. There was no relationship between TIL, peripheral blood changes, and recurrence rate.

Conclusions: It was suggested that changes in CD4+ TILs immediately after treatment initiation and changes in inflammatory blood factors during treatment may be useful for predicting the reduction rate and TRG. These changes begin early during treatment and may be useful in predicting efficacy.