Infiltrating stromal immune cells in inflammatory breast cancer are associated with an improved outcome and increased PD-L1 expression

Background

Inflammatory breast cancer (IBC) is a rare and rapidly progressive form of invasive breast cancer. The aim of this study was to explore the clinical evolution, stromal tumour-infiltrating lymphocytes (sTIL) infiltration and programmed death-ligand 1 (PD-L1) expression in a large IBC cohort.

Patients and methods

Data were collected prospectively from patients with IBC as part of an international collaborative effort since 1996. In total, 143 patients with IBC starting treatment between June 1996 and December 2016 were included. Clinicopathological variables were collected, and sTIL were scored by two pathologists on standard H&E stained sections. PD-L1 expression was assessed using a validated PD-L1 (SP142) assay. A validation cohort of 64 patients with IBC was used to test our findings.

Results

Survival outcomes of IBC remained poor with a 5-year overall survival (OS) of 45.6%. OS was significantly better in patients with primary non-metastatic disease who received taxane-containing (neo)adjuvant therapy (P = 0.01), had a hormone receptor-positive tumour (P = 0.001) and had lower cN stage at diagnosis (P = 0.001). PD-L1 positivity on immune cells (42.9%) was higher in IBC than in non-IBC in both our patient samples and the validation cohort. Furthermore, PD-L1 expression predicted pCR (P = 0.002) and correlated with sTIL infiltration (P < 0.001). sTIL infiltration of more than 10% of the stroma was a significant predictor of improved OS (HR 0.47, 95% CI 0.27–0.81, P = 0.006) in a multivariate model.

Conclusions

IBC is characterised by poor survival and high PD-L1 immunoreactivity on sTIL. This suggests a role for PD1/PD-L1 inhibitors in the treatment of IBC. Furthermore, we showed that PD-L1 expression predicts response to neo-adjuvant therapy and that sTIL have prognostic significance in IBC.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1108-1) contains supplementary material, which is available to authorized users.

Abstract P2-04-09: The prognostic and predictive effect of tumor infiltrating lymphocytes is not determined by B-cells or PD-L1 expression in inflammatory breast cancer

Background

The tumor stroma with tumor infiltrating lymphocytes (TILs) plays a crucial role in the aggressive inflammatory breast cancer (IBC) phenotype and a gene signature enriched for immunity-related genes showed that response to neo-adjuvant chemotherapy was associated with immunity related processes in IBC. In both IBC and non-inflammatory breast cancer (nIBC), tumors are infiltrated by B-cells, but their role in regulating anti-tumor immunity is not well understood. In this study we looked at the prognostic and predictive effect of B-cells in the immune infiltrate of 178 IBC and 247 nIBC patients.

Methods

TIL scoring was done on standard H&E stained sections of formalin-fixed paraffin-embedded pre-treatment tumor tissue according to international guidelines (Salgado et al., 2015). B-cells in the immune infiltrate were defined as CD79α (clone JCB117) positive cells and scoring was done semi-quantitatively, both intra- and peritumorally. Slides, stained with a validated PD-L1 assay (clone SP142) were scored on immune cells (IC) according to Herbst et al., 2014.

Results

Most of our IBC patients presented with a grade 3 (67.7%), ductal (91.1%) carcinoma. A quarter of the patients (25.7%) with initially localized disease (71.6%) achieved complete pathological response (pCR) after neo-adjuvant chemotherapy.The mean TIL score was 18.02% (1.0 – 80.0) and 67 out of 156 patients (42,9%) were PD-L1 positive. Categorical scores of the immune infiltrate are summarized in the table.

 Category 1 (&lt; 10%)Category 2 (≥ 10, &lt; 40%)Category 3 (≥ 40 %)TIL score (n=178)34.73% (n= 61)53.4% (n= 95)12.4% (n=22)Intratumoral CD79α score (n= 175)69.1% (n= 121)22.3% (n= 175)8.6 % (n= 15)Peritumoral CD79α score (n= 171)48.5 % (n= 83)38.0 % (n= 65)13.5 % (n= 23)

TILs were significantly higher in oestrogen receptor negative (ER-) groups compared to ER+ groups (21.26% vs. 15.58%, p= 0.017). In IBC, univariate analysis showed that achieving pCR was significantly associated with more TIL infiltration (p&lt; 0.001), PD-L1 IC expression (p= 0.013) and intratumoral CD79α scores (p= 0.036). However, in multivariate analysis the effect of PD-L1 and CD79α positive cells was lost. When corrected for different molecular subtypes the predictive effect of TILs was only present in ER- groups. Survival analysis showed a significant beneficial effect of TILs (p= 0.014) but only in the ER+ groups, while PD-L1, intra- and peritumoral CD79α scores were not significant. Intratumoral CD79α scores correlated with both TIL score (p= 0.024) and PD-L1 expression (p= 0.007) in multivariate analysis.

When comparing IBC to nIBC, TILs were significantly higher in IBC patients (15.58 % vs. 11.29%, p= 0.009) in the ER+ group, while in the ER- group they were significantly lower (21.27% vs. 37.19%, p &lt; 0.001). This was also seen for CD79α peritumoral positivity, but logistic regression revealed that this was a TILs effect.

Conclusion

A high TIL score correlates with a better OS and pCR in IBC, depending on the ER status. B-cells and PD-L1 expressing IC appear not to contribute to this effect, but do correlate independently with each other. Further research is needed to unravel the driving and targetable components of the immune responses in IBC.

Citation Format: Van Berckelaer C, Parizel M, Van Dam P, Dirix L, Rypens C, Bertucci F, Schats KA, Kockx MM, Van Laere S, Colpaert C. The prognostic and predictive effect of tumor infiltrating lymphocytes is not determined by B-cells or PD-L1 expression in inflammatory breast cancer [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 P2-04-09.

PDL1 expression in inflammatory breast cancer is frequent and predicts for the pathological response to chemotherapy

We retrospectively analyzed PDL1 mRNA expression in 306 breast cancer samples, including 112 samples of an aggressive form, inflammatory breast cancer (IBC). PDL1 expression was heterogeneous, but was higher in IBC than in non-IBC. Compared to normal breast samples, PDL1 was overexpressed in 38% of IBC. In IBC, PDL1 overexpression was associated with estrogen receptor-negative status, basal and ERBB2-enriched aggressive subtypes, and clinico-biological signs of anti-tumor T-cell cytotoxic response. PDL1 overexpression was associated with better pathological response to chemotherapy, independently of histo-clinical variables and predictive gene expression signatures. No correlation was found with metastasis-free and overall specific survivals. In conclusion, PDL1 overexpression in IBC correlated with better response to chemotherapy. This seemingly counterintuitive correlation between expression of an immunosuppressive molecule and improved therapeutic response may be resolved if PDL1 expression is viewed as a surrogate marker of a strong antitumor immune response among patients treated with immunogenic chemotherapy. In such patients, PDL1 inhibition could protect activated T-cells or reactivate inhibited T-cells and improve the therapeutic response, notably when associated with immunogenic chemotherapy.