Abstract P2-04-13: Difference of immune microenvironment between primary and recurrent tumours in breast cancer patients

Abstract

Abstract Background Immune checkpoint therapy only benefits a fraction of patients, thus huge efforts have been made to develop predictive biomarkers to identify those patients. Immune biomarkers like PD-L1 expression are extremely dynamic and the timing of evaluation, on primary or metastatic disease, may be critical. We have already shown that tumour-infiltrating lymphocytes (TILs) decrease during metastatic progression in triple-negative (TN) and human epidermal growth factor-2 positive (HER2+) breast cancers (Ogiya R, ASCO 2015), suggesting that mechanisms of immune escape contribute and favour the metastatic progression. In this work we aimed to characterize the modulation and changes of specific immune markers during the metastatic spread comparing paired samples from primary and recurrent breast cancers. Methods We retrospectively identified 25 patients with HER2+ (n = 14) and TN (n = 11) early breast cancer diagnosed between 1990 and 2009 at Tokai University Hospital, and who subsequently experienced a first regional or distant recurrence confirmed by tumour biopsy/resection. Haematoxylin and eosin-stained slides of these paired samples were evaluated for stromal TILs. Immunohistochemical staining was performed using primary antibodies against CD4, CD8, Foxp3, PD-L1, PD-L2, and HLA-class I. Results The sites of first recurrence was the skin (n = 7), brain (n = 6), lymph node (n = 4), lung (n = 3), bone (n = 2), and one of each of bone marrow, liver and muscle. Immunohistochemical evaluations could not be performed in 5 primary tumours and 2 recurrent tumours because of the small quantity of the specimens. The percentage of CD8+ T cells staining in the primary tumours was significantly higher (median 16%) than that in recurrent tumours (median 10%) (paired t-test, p = 0.008) Similarly, the percentage of CD4+ T cells staining in the primary tumours was significantly higher (median 40%) than that in recurrent tumours (median 25%) (p = 0.026). The percentage of Foxp3+ T cells was low (<10%) and similar in both primary and recurrent tumours (p = 0.16). PD-L1, PD-L2, and HLA class I antibody expression was not statistically different between primary and recurrent tumours, but conversions from positive to negative and vice versa were observed. PD-L1+ staining (≥1%) was 90% and 85% in primary and metastatic tumours, respectively. Comparison of positivity rate between primary and recurrent tumours for each antibody Primary tumourRecurrent tumourPTotal breast tumours (N)2023 TILs positivity rate, median (%) CD440%25%.03CD816%10%.01Foxp3<10%<10%.16Expression in tumour cells (N) PD-L1 Strong85.46Weak1015 Negative23 PD-L2 Strong69.78Weak1011 Negative43 HLA Strong46.89Weak1415 Negative22 Conclusions Tumours at first metastatic recurrence in HER2+ and TN breast cancers have a lower percentage of both CD8+ and CD4+ T cells compared to primary tumours, confirming a potential role of immune escape in tumour progression. Other immune markers, including PD-L1, were not found to change significantly, but negative/positive conversions were observed. This suggest that an evaluation of disease at the time of immunotherapy administration might be more informative. These findings warrant larger confirmation studies. Citation Format: Ogiya R, Niikura N, Kumaki N, Bianchini G, Kitano S, Iwamoto T, Hayashi N, Yokoyama K, Oshitanai R, Terao M, Morioka T, Tsuda B, Okamura T, Saito Y, Suzuki Y, Tokuda Y. Difference of immune microenvironment between primary and recurrent tumours in breast cancer patients [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-04-13.