Abstract 426P
Background
Preoperative chemoradiotherapy can enhance antitumor immunity through increasing T-cell activation and tumor infiltration. These effects could potentially sensitize tumors to immunotherapies, including checkpoint inhibitors. We explored whether preoperative therapy for locally advanced rectal cancer induces immunologic changes.
Methods
We analyzed by immunohistochemistry 55 locally advanced rectal cancers from the STAR-01 cohort. Paired pre- and post-operative specimens were available for 25 out of 55 patients. The multicenter STAR-01 study enrolled patients treated with preoperative chemoradiation with or without oxaliplatin. The immunoistochemical analysis was performed with a panel of immune cells and associated factors as CD3, CD20, CD4/CD8, PD1 and FoxP3. The pattern of tumor infiltrating lymphocytes (TILs) and related infiltrating lymphocytes (RILs) was also evaluated. Response to preoperative chemoradiotherapy was assessed according to tumor regression grade (TRG sec. Ryan –AJCC Eight ed.).
Results
The expression level of CD3+, CD20+, FoxP3+ and PD1+ cells were not significantly different after therapy. The TILs and RILs immunosuppressive cells were higher in better responder (TRG0), although we did not find any statistical significance given the small sample size. Decreasing CD4/CD8 ratio on post-operative samples was significantly associate with TRG 0 (p <0.01). The increase of lymphocyte CD8+ was related to a good pathological response after chemoradiotherapy.
Conclusions
Our data suggest that chemoradiotherapy may induce an enrichment of CD8+ T lymphocytes in good responders. The new frontier of best treatment could be the use of specific immune cells (T lymphocytes) to activate the system's response immune against disease.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Azienda Ospedaliero-Universitaria di Parma.
Funding
SNUPI OdV.
Disclosure
All authors have declared no conflicts of interest.