Abstract 5701: Verification of the methodology for evaluating tumor-infiltrating lymphocytes in colorectal cancer

Abstract

Abstract Background: The density of tumor-infiltrating lymphocytes (TILs) have been reported to reflect antitumor immune response and correlate with prognosis in malignancy. However, the methodology for evaluating the density of TILs by an immunohistochemical analysis differs among reports. The aim of this study was to verify the methodology for evaluating the density of TILs by immunohistochemical analysis and thereby identify the optimum methodology in clinical setting. Methods: Three-hundred-thirteen patients who underwent curative operation for stage II/III colorectal cancer were enrolled. We retrospectively examined the density of TILs using immunohistochemical staining according to each method as follows: 1) subset of lymphocytes (i.e. CD4+/CD8+), 2) selected fields (i.e. at random or focusing on hot spots), 3) location in low-power field (i.e. the invasive margin [TILsIM] or the center of the tumor [TILsCT] or the surface of the tumor [TILsST]), and 4) location in high-power field (i.e. in tumor stroma [sTILs] or intra-tumor cells [iTILs] or total TILs [tTILs: sTILs+iTILs]). We then assessed the prognostic value of the density of TILsIM evaluated as described above. We also evaluated the correlation between the density of TILsIM and that of TILsCT/TILsST. Results: In randomly selected fields, the densities of CD8+sTILsIM and CD8+tTILsIM were significantly associated with the survival. However, the densities of TILs evaluated via other methods were not associated with the survival. Furthermore, the density of CD8+TILsIM was significantly associated with that of CD8+TILsCT and CD8+TILsST. Conclusions: We concluded that best and easiest way to evaluate the density of TILs in the clinical setting may be to assess the density of total CD8+TILs at the invasive margin in randomly selected fields. Citation Format: Shinji Matsutani, Masatsune Shibutani, Kiyoshi Maeda, Hisashi Nagahara, Tatsunari Fukuoka, Tatsuro Tamura, Go Ohira, Sadaaki Yamazoe, Kenjiro Kimura, Takahiro Toyokawa, Ryosuke Amano, Hiroaki Tanaka, Kazuya Muguruma, Kosei Hirakawa, Masaichi Ohira. Verification of the methodology for evaluating tumor-infiltrating lymphocytes in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5701.