Abstract P5-02-44: Efficacy analysis of CDK4/6 inhibitors in combination with endocrine therapy treatment in HR+/HER2- breast cancer according to PAM50 intrinsic subtype: primary results of SOLTI-1801_CDK-PREDICT study

Background: First-line treatment with cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) plus endocrine therapy (ET) has demonstrated efficacy in improving progression-free survival (PFS), overall response rate (ORR) and, more recently, ribociclib was also improve overall survival (OS) in hormone receptor-positive/HER2-negative (HR+/HER2-) advanced breast cancer (aBC). Unfortunately, most patients eventually progress and develop secondary or primary endocrine resistance. To date, no clinical or molecular markers have shown clinical utility in this setting. However, data from retrospective analysis suggest that intrinsic subtypes (IS) are prognostic and predict benefit from CDK4/6i+ET (Finn SABCS 2017, Prat. JCO 2021). Here, we have evaluated the impact of IS in PFS and ORR.

Methods: This study prospectively evaluated patients with HR+/HER2- aBC treated in the first-line setting with CDK4/6i + ET from February 2015 to January 2022 across 5 hospitals in Spain. Tumor biopsies had been performed within 90 days prior the patient started the CDK4/6i + ET. RNA from FFPE tumors was analyzed at the nCounter® (Nanostring Technologies) using a 72 custom gene panel including the PAM50 genes. The primary objective is to correlate the baseline PAM50 IS with PFS. The Kaplan-Meier method and multivariable cox model PFS analyses were performed adjusting for previous endocrine sensitivity, visceral disease, and metastatic onset disease. Secondary objectives were to estimate the ORR based on RECIST1.1 and its association with IS and the development of a prognostic algorithm that includes clinical and genomic data.

Results: From May 2020 to May 2022, 113 patients with PAM50 results who met all eligibility criteria, including sample quality, were included. IS distribution was 42.5% Luminal A, 46.9% luminal B, 7.1% HER2-enriched, 0.9% basal-like and 2.6% Normal-like (89.4% luminal vs 10.6% non-luminal). Baseline patient characteristics are shown in table 1. The median follow-up for PFS was 18.5 m (interquartile range 10.0 – 31.7m). Median PFS for Luminal vs no-luminal subtypes was 26.8 m (95% CI: 18.9 - 43.8 m) and 10.0 m (95% CI: 5.8 - 26.0 m) (adjusted hazard ratio [aHR]= 2.44 95% IC: 1.17 - 5.07). Median PFS by all IS was not reached (NR) for Luminal A (95% CI: 23.0 – NR); 19.5 m luminal B (95% CI: 15.7 - 27.3 m, aHR vs Luminal A= 1.98 95% IC: 1.09 - 3.62), 10.0 m HER2-E (95% CI: 4.4 - NR, aHR vs Luminal A= 2.75 95% IC: 1.05 - 7.18), 12.4 m Normal-like (95% CI: 5.8 - NR, aHR vs Luminal A= 19.35 95% IC: 2.32 - 160.89) and not estimable for basal-like (aHR vs Luminal A= 5.44 95% IC: 1.44 - 20.60). ORR was not significantly higher in Luminal B (55.1%) and HER2-E (57.1%) subtype versus luminal A (46.3%) (p=0.677). OS follow-up is still immature.

Conclusions: We confirmed the independent prognostic value of the PAM50 IS in first-line HR+/HER2- breast cancer treated with CDK4/6i+ET. Further gene expression analysis and development of a prognostic composite score is ongoing and will be presented at the conference.

This project has received a research grant from “Instituto de Salud Carlos III (ISCIII), Ministerio de Economía y Competitividad” (Spain) awarded within the National Research Program with reference PI 18/01408, co-funded with European Union ERDF funds.

Baseline patient characteristics

Citation Format: Pablo Tolosa, Tomás Pascual, Cristina Hernando, Sonia Servitja, Adela Fernández, Fara Brasó-Maristany, Javier Benitez, Laura Lema, Yolanda Ruano, Lucia Parrilla, Ana María Roncero, Rodrigo Sánchez-Bayona, Manuel Alva, Guillermo Villacampa, María Rocío Moreno-Villa, Jordi Canes, Fernando Salvador, Aleix Prat, Eva Ciruelos. Efficacy analysis of CDK4/6 inhibitors in combination with endocrine therapy treatment in HR+/HER2- breast cancer according to PAM50 intrinsic subtype: primary results of SOLTI-1801_CDK-PREDICT study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-44.

Abstract OT2-19-03: Solti-1801. Analysis of the efficacy of CDK4/6 inhibitors in combination with hormonal treatment in luminal breast cancer in relation to the intrinsic subtype and markers of immunity (CDK-predict)

Introduction. The incorporation of cyclin-dependent kinase inhibitors 4 and 6 (CDK4/6 inhibitors) with endocrine therapy in patients with hormone receptor-positive/HER2-negative (HR+/HER2-) advanced breast cancer has demonstrated its efficacy improving progression-free survival (PFS), overall response rate (ORR) and, more recently, overall survival (OS). However, patients eventually progress due to resistance to treatment. To date, no clinical or molecular markers defining the HR+/HER2- patient population that obtains the greatest benefit from these drugs have been found, apart from estrogen receptor positivity. However, data from multiple retrospective analysis suggest that within HR+/HER2- disease, the non-luminal intrinsic subtypes (20-30% of these patients) have a worse prognosis and may not benefit equally from every CDK4/6 inhibitor (Finn SABCS 2017, Prat. JCO 2021). Furthermore, the prognostic impact of tumor infiltrating lymphocytes (TILs) and gene expression related to the immune response in the context of HR+/HER2- advanced breast cancer have not been deeply investigated. Design. CDK-PREDICT is an observational, non-interventional, multicenter study that will include 114 patients with advanced breast cancer treated in first-line with CDK4/6 inhibitors + hormone therapy. The primary objective is to correlate the baseline intrinsic subtypes (defined by PAM50) with the efficacy (measured as PFS) of CDK4/6 inhibitors + hormone therapy. As secondary objectives, the correlation of the intrinsic subtypes with ORR and with the histopathological characteristics of the tumor will be analyzed. In addition, the expression of immune response and cell cycle genes, as well as the presence of TILs, will be correlated with the intrinsic subtypes and with PFS and ORR. Formalin-fixed paraffin-embedded (FFPE) tumor tissue samples will be hematoxylin and eosin (H&E) stained and percentage of TILs will be determined. RNA will be purified and analyzed at the nCounter (Nanostring Technologies) using a panel of 72 genes including the PAM50 genes and immune genes such as PD1, PDL1, CD8 or CD4. Overall, we aim to develop a predictive score combining clinical, genomic, and immune expression data integrating tumor biology and microenvironment. For inclusion in the study, a metastatic sample taken within 100 days prior to CDK4/6 inhibitors treatment is required. Once this sample has been collected, registered, and assessed for quality, patients will be followed up every 6 months until disease progression, death or withdrawal from the study. As of July 2021, 80 patients have been included at 5 sites in Spain. This study is included within the Biomarker program of SOLTI. Recruitment of this study started in June 2020. Acknowledgements.This project has received a research grant from “Instituto de Salud Carlos III (ISCIII), Ministerio de Economía y Competitividad” (Spain) awarded within the National Research Program with reference PI 18/01408, co-funded with European Union ERDF funds (European Regional Development Fund).

Citation Format: Pablo Tolosa, Tomás Pascual, Cristina Hernando, Sonia Servitja, María Fernández Abad, Fara Brasó-Maristany, Javier Benítez, Laura Lema, Mario Martínez, Yolanda Ruano, Lucía Parrilla, Alejandra Bernardini, Ana María Roncero, Laia Paré, Jordi Canes, Patricia Villagrasa, Fernando Salvador, Aleix Prat, Eva Ciruelos. Solti-1801. Analysis of the efficacy of CDK4/6 inhibitors in combination with hormonal treatment in luminal breast cancer in relation to the intrinsic subtype and markers of immunity (CDK-predict) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-19-03.

Abstract OT-26-04: Solti-1801. Analysis of the efficacy of CDK4/6 inhibitors in combination with hormonal treatment in luminal breast cancer in relation to the intrinsic subtype and markers of immunity (CDK-PREDICT)

Introduction. The incorporation of cyclin-dependent kinase inhibitors 4 and 6 (CDK4/6 inhibitors) with endocrine therapy in patients with advanced hormone receptor-positive (HR+) breast cancer and without overexpression of the HER2 (HER2-) oncogene has demonstrated its efficacy improving progression-free survival (PFS), overall response rate (ORR) and, more recently, overall survival (OS). However, patients eventually progress due to resistance to treatment. To date, no clinical or molecular markers defining the HR +/HER2- patient population that obtains the greatest benefit from these drugs have been found, apart from estrogen receptor positivity. However, there are data from multiple retrospective analysis suggesting that within HR+/ HER2- disease, the non-luminal intrinsic subtypes (20-30% of these patients) have a worse prognosis and may not benefit from CDK4/6 inhibitors. Furthermore, the prognostic impact of tumor infiltrating lymphocytes (TILs) and gene expression related to the immune response in the context of HR + / HER2- advanced breast cancer have not been deeply investigated.

Design. CDK-PREDICT is an observational, non-interventional, multicenter study that will include 114 patients with advanced breast cancer who have received, are receiving or are going to receive endocrine therapy plus a CDK4/6 inhibitor for, at least, 8 weeks as first-line treatment. The primary objective is to correlate the intrinsic subtypes (defined by PAM50) with the efficacy (measured as PFS) of CDK4/6 inhibitors + hormone therapy. As secondary objectives, the correlation of the intrinsic subtypes with ORR and with the histopathological characteristics of the tumor will be analyzed. In addition, the expression of immune response and cell cycle genes, as well as the presence of TILs, will be correlated with the intrinsic subtypes and with PFS and ORR. Overall, we aim to develop a predictive score combining clinical, genomic and immune expression data integrating tumor biology and microenvironment. For inclusion in the study, a metastatic sample taken within 90 days prior to CDK4/6 inhibitors treatment will be required. Once this sample has been collected, registered and assessed for quality, patients will be followed up every 6 months until disease progression, death or withdrawal from the study.

This project has received a research grant from “Instituto de Salud Carlos III (ISCIII), Ministerio de Economía y Competitividad” (Spain) awarded within the National Research Program with reference PI 18/01408, co-funded with European Union ERDF funds (European Regional Development Fund). This study is included within the Biomarker program of SOLTI. Recruitment of this study started in June 2020.

Citation Format: Pablo Tolosa, Tomás Pascual, Cristina Hernando, Sonia Servitja, María Fernández Abad, Rafael Villanueva, Fernando Henao, Javier Benítez, Laura Lema, Mario Martínez, Yolanda Ruano, Lucía Parrilla, Alejandra Bernardini, Ana María Roncero, Laia Paré, Jordi Canes, Fernando Salvador, Patricia Villagrasa, Aleix Prat, Eva Ciruelos. Solti-1801. Analysis of the efficacy of CDK4/6 inhibitors in combination with hormonal treatment in luminal breast cancer in relation to the intrinsic subtype and markers of immunity (CDK-PREDICT) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-26-04.

Contribution of JAK2 mutations to T-cell lymphoblastic lymphoma development

The JAK-STAT pathway has a substantial role in lymphoid precursor cell proliferation, survival and differentiation. Nonetheless, the contribution of JAK2 to T-cell lymphoblastic lymphoma (T-LBL) development remains poorly understood. We have identified one activating TEL-JAK2 translocation and four missense mutations accumulated in 2 out of 16 T-LBL samples. Two of them are novel JAK2 mutations and the other two are reported for the first time in T-LBL. Notably, R683G and I682T might have arisen owing to RNA editing. Mutated samples showed different mutated transcripts suggesting sub-clonal heterogeneity. Functional approaches revealed that two JAK2 mutations (H574R and R683G) constitutively activate JAK-STAT signaling in γ2A cells and can drive the proliferation of BaF3-EpoR cytokine-dependent cell line. In addition, aberrant hypermethylation of SOCS3 might contribute to enhance the activation of JAK-STAT signaling. Of utmost interest is that primary T-LBL samples harboring JAK2 mutations exhibited increased expression of LMO2, suggesting a mechanistic link between JAK2 mutations and the expression of LMO2, which was confirmed for the four missense mutations in transfected γ2A cells. We therefore propose that active JAK2 contribute to T-LBL development by two different mechanisms, and that the use of pan-JAK inhibitors in combination with epigenetic drugs should be considered in future treatments.

The stromal gene encoding the CD274 antigen as a genetic modifier controlling survival of mice with γ-radiation-induced T-cell lymphoblastic lymphomas

Using an inter-specific subcongenic strain, Nested Recombinant Haplotype 3 (NRH3), generated between two mouse strains showing extreme differences in γ-radiation-induced thymic lymphoma susceptibility (SEG/Pas and C57BL/6J), we have identified a critical region on chromosome 19 that regulates survival of mice suffering from T-cell lymphoblastic lymphomas. Mapped on this region, the gene encoding the Cd274 ligand is able to trigger an inhibitory effect that modulates T-cell receptor (TCR) signalling and affects thymocyte maturation. Interestingly, this gene shows differential expression between thymic stromal cells from both strains in early response to a single sublethal γ-ray dose, but is inhibited in T-cell lymphoblastic lymphomas. Furthermore, we have identified several polymorphisms in the complementary DNA sequence of this gene that affect the affinity for its Cd279 receptor and are able to induce a differential rate of thymocyte apoptosis. Taken together, our data are consistent with Cd274 acting as a genetic modifier that influences the survival of γ-radiation-induced T-cell lymphoma-bearing mice. The data similarly support the idea of a co-evolution of tumour cells and associated stromal cells to generate a favourable microenvironment for T-cell lymphoma growth.