Abstract P1-10-21: PD-L1 expression of tumor infiltrating immune cells has potential as a biomarker in triple-negative breast cancers

[background] In general, TNBC has a high distant metastasis rate and is highly aggressive. Despite good response to chemotherapy, it has a poorer prognosis compared to other subtypes. There is a need to develop new treatments for the selection of appropriate treatments. At present, treatments using an immune check point blockade are attracting attention, and the evaluations as biomarkers of and, PD-1 / PD-L1 expression on immune cells for therapeutic effects and prognosis in TNBC are controversial. In order to select patients with TNBC for who immunotherapy is likely to be effective, new biomarkers need to be explored. [Purpose] Our aim is to investigate the possibility as a biomarker of PD-L1 expression on immune cells(PD-L1/IC) in TNBC. We also assess the relationship among PD-L1/IC, PD-L1 expression on tumor cells(PD-L1/TC) and TIL. [Methods] This study included 248 patients with primary TNBC who underwent resection without neoadjuvant chemotherapy at Kyushu University Hospital(Fukuoka, Japan) and related hospitals between January 2004 and December 2014. [Results] PD-L1/IC was positive in 129 cases (52.0%) of 248 TNBCs. Although there was no significant difference in RFS and OS between the positive and negative groups, PD-L1/IC-positive and TIL-High group showed the best prognosis, considering the combination whether PD-L1/IC was positive or negative, and TIL was high or low. PD-L1/IC was significantly correlated with PD-L1/TC(p [Conclusion] In TNBC, the relationship between PD-L1/IC and prognosis is still not clear, but in IMpassion130 trial, PD-L1/IC is a predictive marker for the effect of Atezolizumab. PD-L1/IC has potential as an immune biomarker in TNBCs. This study also found that PD-L1/IC was related to the therapeutic effect of anthracycline. PD-L1/IC may be a predictive marker of the efficacy of various treatments. Citation Format: Yurina Harada, Makoto Kubo, Hitomi Mori, Masaya Kai, Mai Yamada, Kanako Kurata, Hitomi Kawaji, Kazuhisa Kaneshiro, Saori Hayashi, Akiko Shimazaki, Takafumi Morisaki, Rin Yamaguchi, Nobuyuki Arima, Reiki Nishimura, Masayuki Okido, Masafumi Nakamura. PD-L1 expression of tumor infiltrating immune cells has potential as a biomarker in triple-negative breast cancers [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-10-21.