Conventionally neoadjuvant radiotherapy regimens for rectal cancer are long-course radiotherapy in combination with chemotherapy (LCRT) and short-course radiotherapy (SCRT). We aimed to compare the different immune microenvironment in patients between two the different radiotherapy regimens.
The expression of LAG-3, CD8 and CD3 was detected by immunohistochemistry on specimen of 76 rectal cancer patients following neoadjuvant treatment. The expression of proteins was assessed as the percentage of positive cells (PP). The variation of proteins expression was compared by Mann-Whitney U test analysis.
LCRT was given in 40 (52.6%) patients and the rest 36 (47.4%) patients were SCRT. The median PP of immune cells LAG-3 expression was 15% (range, 0% - 80%) in all patients. The expression of CD8 and CD3 were 10% (range, 0 - 80%) and 30% (range, 0 - 90%), respectively. The LAG-3 expression was high in patients with SCRT compared to LCRT (22.5% vs. 8.0%, P = 0.0440). On the contrary, CD8+ cells were high in LCRT (15% vs. 8%, P = 0.0146). No difference was observed in CD3+ cells.
Tumor microenvironment might be modified by different fractions and dose. Immune cells LAG-3 expression were high with respect to SCRT. The diverse expression pattern of LAG-3 between SCRT and LCRT supporting the different combination strategies of immune checkpoint blockade and neoadjuvant radiotherapy.
Clinical trial identification
Legal entity responsible for the study
National Clinical Key Specialty Construction Program, The Fujian Province Natural Science Foundation (2017J01260).
All authors have declared no conflicts of interest.