Background:

Characterization of the immunological microenvironment has been demonstrated to be associated with prognosis and the effect of chemotherapy of various cancers. Then it has been shown by their role several studies in 5-FU-based neoadjuvant chemoradiotherapy for rectal cancer. However, their role in neoadjuvant chemotherapy (NAC) for rectal cancer remains unknown. The objective of this study was to examine the relationship between immune reactions and the pathological response to induction oxaliplatin-based NAC in patients with advanced rectal cancer.

Methods:

A total of 65 patients with advanced rectal cancer who underwent induction oxaliplatin-based NAC followed by surgical resection were enrolled. The resected tumor specimens were counted positive cell of tumor infiltrating lymphocytes (TILs) and macrophages by using immunohistochemical staining for CD3, CD8, Foxp3, CD86, CD206. We analyzed for the relationship between the numbers of TILs or macrophages at the stroma in resected specimens and the pathological response to induction oxaliplatin-based NAC.

Results:

The numbers of Foxp3+ TILs in resected specimens were strongly correlated with pathological response. Patients with higher number of Foxp3+ TILs showed poor pathological response (p<0.001). There were no statistically significant differences between the number of CD3+, CD8+ TILs and pathological response, but patients with higher ratio of CD8+/FOXP3+ TILs was associated with good pathological response (p = 0.023). No associations were observed between the numbers of CD86+, CD206+ macrophages and pathological response.

Conclusions:

In rectal cancer patients, T lymphocyte-mediated immune reactions significantly correlated with pathological response of oxaliplatin-based NAC for advanced rectal cancer. These were similar to the T lymphocyte-mediated immune responses in the neoadjuvant radiation therapy for rectal cancer.

Citation Format: Kentaro Sekizawa, Yasushi Ichikawa, Atsushi Ishibe, Hirokazu Suwa, Masashi Momiyama, Ikuma Kato, Mitsuyoshi Ota, Itaru Endo. Relationship of characterization of the immunological microenvironment and pathological response in advanced rectal cancer after oxaliplatin-based neoadjuvant chemotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4894.