Pembrolizumab in Lymphopenic Metastatic Breast Cancer Patients Treated with Metronomic Cyclophosphamide: A Clinical and Translational Prospective Study

Abstract

Purpose

Metastatic endocrine-resistant breast cancer (MBC) is a disease with poor prognosis and few treatment options. Low lymphocyte count is associated with limited overall survival. In a prospective cohort of lymphopenic patients with HER-2 negative MBC, we assessed the clinical and biological impact of pembrolizumab combined with metronomic cyclophosphamide.

Experimental Design

This multicenter Phase II study evaluated the safety and clinical activity of pembrolizumab (intravenous (IV), 200mg, every 3 weeks) combined with metronomic cyclophosphamide (50mg/day, per os) in lymphopenic adult patients with HER2-negative MBC previously treated by at least one line of chemotherapy in this setting according to a Simon’s minimax two-stage design. Blood and tumor samples were collected to assess the impact of the combined treatment on circulating immune cells and the tumor immune microenvironment through multiparametric flow cytometry and multiplex immunofluorescence analyses. Primary endpoint was the clinical benefit rate at 6 months of treatment (CBR-6M). Secondary endpoints were objective response rate (ORR), duration of response, progression free survival (PFS), and overall survival (OS).

Results

Two out of the twenty treated patients presented clinical benefit (one Tumor Mutational Burden (TMB)-high patient with complete response (CR) and one patient with objective response (OR) per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST V1.1) associated with a strong increase of cytokine-producing and proliferating CD4⁺ T cells and higher CD8⁺ T cells to macrophage ratios in the tumor. This impact on CD4⁺ and CD8⁺ T cell polyfunctionality was still observed more than one year for the patient with CR. A decreased in their absolute number of CD4⁺ and CD8⁺ memory T cells was observed in other patients.

Conclusion

Pembrolizumab combined with metronomic cyclophosphamide was well tolerated, and displayed limited anti-tumoral activity in lymphopenic MBC. Correlative translational data of our trial advocates for additional studies with other chemotherapy combinations.

Keywords:

• metastatic breast cancer
• lymphopenia
• immunotherapy
• chemotherapy
• immunomonitoring

Data Sharing Statement

The data sets generated during the current study are available from the corresponding author on reasonable request.

Ethical Approval

This study was conducted in accordance with the Declaration of Helsinki, International Conference on Harmonization-and Good Clinical Practice. All patients provided written informed consent and ethics approval for this study was approved by the Ethics Committee of the Leon Berard Cancer Center. Consent to publish was also approved.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

Benoîte Mery and Christine Ménétrier-Caux are co-first authors for this study. Bertrand Dubois and Olivier Trédan are co-last authors for this study. Dr Pierre-Etienne Heudel reports personal fees, non-financial support from PFIZER, GILEAD, NOVARTIS, SEAGEN, LILLY; personal fees from MSD, during the conduct of the study. Professor Isabelle Ray-Coquard reports grants, personal fees from MSD and BMS; personal fees from Astra ZENECA, GSK, CLOVIS, ROCHE, DAICHI, MERSANA, Immunogen, Pharmamar, during the conduct of the study. Dr Thomas Bachelot reports grants, personal fees, non-financial support from Novartis, AstraZeneca, Daiichi, Pfizer; grants, personal fees from SeaGen, outside the submitted work. Dr Paule Augereau reports personal fees, non-financial support from AstraZeneca, GSK, Seagen; personal fees from Novartis, outside the submitted work. Dr David Perol reports personal fees, travel funding from ROCHE, personal fees from TAKEDA, ASTRAZENECA, BAYER, BOEHRINGHER-INGELHEIM, BRISTOL-MYERS SQUIBB, DAIICHI-SANKYO, ELI-LILLY, IPSEN, NOVARTIS, MERCK SHARP AND DOHME, JANSSEN, PFIZER, outside the submitted work. Dr Olivier Trédan reports grants, personal fees from MSD, during the conduct of the study. The authors report no other conflicts of interest in this work.

Additional information

Funding

This work was an investigator-initiated trial (no grant number is applicable). CLB was the legal sponsor. MSD provided the investigational agent and funding, but had no role in the study design, data collection, analysis, interpretation, writing of the report, or decision to publish this report. The database is held by CLB, and CLB statisticians carried out the analysis. Research grants were perceived from “INCa” (PRT-K INCA 2009-113 (BreastImmun), Transla13-097 (Camel), Transla13-061 (TNBT)), “Lyrican” (LYRICAN INCa-DGOS-Inserm_12563), “Ruban Rose” for the blood immuno-monitoring and “Région Rhône-Alpes” (IRICE project) for the development of multiplex immunofluorescence staining.