Abstract P4-08-13: Prognostic significance of CD8+ tumor-infiltrating lymphocytes (TILs) in patients with early breast cancer (EBC) treated with dose-dense sequential adjuvant chemotherapy (dds-CT). An observational study (ACTRN12616001043426)

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Abstract Background - aim: Information on the prognostic role of cytotoxic CD8+ T cells in the era of modern adjuvant CT is limited. The primary objective of the present report is to assess the prognostic impact of CD8+ cells in patients with intermediate or high-risk EBC (T1-3N1-2M0) treated with dds-CT. Secondary endpoints are safety, disease-free survival (DFS) and overall survival (OS). Patients and Methods: Patients (N=1,000) were treated with 4 cycles of Epirubicin, 75mg/m2, and Cyclophophamide, 600mg/m2 every 2 weeks followed by 4 cycles of Docetaxel (D), 100mg/m2 every 3 weeks with G-CSF support in all cycles. Trastuzumab was initiated concurrently with D and continued for a total of 1 year. Hormonal and radiation therapy were given post CT, as indicated. Formalin-fixed paraffin-embedded tumors were available for 642 patients (64.2%) and were centrally assessed for immunohistochemical subtypes (IHC4; N=526), stromal TILs density by morphology (N=636), as well as stromal and intratumoral cytotoxic CD8+ T cell numbers (N=554). TILs and CD8+ were assessed as continuous variables for associations and as 10% increments for outcome. Results: In total, 901/1,000 pts (90.1%) completed 8 cycles of CT. Severe (gradeIII-IV) toxicitiesincludedneutropenia (5.6%), leucopenia (3.6%), lymphopenia (2.1%), hand-footsyndrome (2.1%), and hepatotoxicity (1.8%). Febrileneutropenia occurred in 1.6% of the patients. The 5-year DFS and OS rates were 89.5% and 93.1%, respectively. Luminal A tumors were classified in 26.2%, Luminal B in 35.2%, luminal HER2 in 9.5%; HER2-enriched in 7.2%; and, triple-negative (TNBC) in 21.9% of informative patients. Among subtypes, stromal TILs density was higher in HER2-enriched and TNBC (p<0.001); intratumoral CD8+ values were higher in TNBC (p<0.001); and, stromal CD8+ were higher in HER2-enriched (p=0.034). In all patients, TILs density and intratumoral CD8+ cell numbers were not associated with DFS and OS, while increased stromal CD8+ were marginally associated with prolonged DFS (HR=0.98, 95%CI 0.96-1.00, p=0.066).Adjusted for histological grade, menopausal, ER/PgR and nodal status, higher stromal CD8+ were associated with prolonged DFS (HR=0.98, 95% CI 0.96-1.00, p=0.043). In TNBC, higher stromal TILs density conferred prolonged DFS (HR=0.97, 95%CI 0.94-0.99, p=0.029), which retained its prognostic significance in multivariate analysis (HR=0.97, 95% CI 0.94-1.00, p=0.049). Conclusions: In this study, dds-CT was well tolerated and active in patients with EBC. We confirm the presence of morphologically assessed higher TILs density, and of higher cytotoxic CD8+ T cell numbers in hormone receptor negative EBC, as well as the favorable prognostic impact of higher stromal TILs density in TNBC. In comparison to stromal TILs density, higher stromal CD8+ may confer favorable prognosis irrespectively of EBC subtype. Stromal CD8+ seems to be a marker worth further standardizing for reporting on immune cell infiltrates in EBC. Citation Format: Kourea HP, Koletsa T, Kotoula V, Koliou G-A, Batistatou A, Pentheroudakis G, Arapantoni-Dadioti P, Zagouri F, Bobos M, Sotiropoulou M, Papoudou-Bai A, Chrisafi S, Efstratiou I, Aravantinos G, Nicolaou I, Gogas H, Visvikis A, Christodoulou C, Petraki C, Koutras A, Psyrri A, Pectasides D, Fountzilas G. Prognostic significance of CD8+ tumor-infiltrating lymphocytes (TILs) in patients with early breast cancer (EBC) treated with dose-dense sequential adjuvant chemotherapy (dds-CT). An observational study (ACTRN12616001043426) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-08-13.

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