ESMO expert consensus statements (ECS) on the definition, diagnosis, and management of HER2-low breast cancer

Human epidermal growth factor receptor 2 (HER2)-low breast cancer has recently emerged as a targetable subset of breast tumors, based on the evidence from clinical trials of novel anti-HER2 antibody-drug conjugates. This evolution has raised several biological and clinical questions, warranting the establishment of consensus to optimally treat patients with HER2-low breast tumors. Between 2022 and 2023, the European Society for Medical Oncology (ESMO) held a virtual consensus-building process focused on HER2-low breast cancer. The consensus included a multidisciplinary panel of 32 leading experts in the management of breast cancer from nine different countries. The aim of the consensus was to develop statements on topics that are not covered in detail in the current ESMO Clinical Practice Guideline. The main topics identified for discussion were (i) biology of HER2-low breast cancer; (ii) pathologic diagnosis of HER2-low breast cancer; (iii) clinical management of HER2-low metastatic breast cancer; and (iv) clinical trial design for HER2-low breast cancer. The expert panel was divided into four working groups to address questions relating to one of the four topics outlined above. A review of the relevant scientific literature was conducted in advance. Consensus statements were developed by the working groups and then presented to the entire panel for further discussion and amendment before voting. This article presents the developed statements, including findings from the expert panel discussions, expert opinion, and a summary of evidence supporting each statement.

Liquid Biopsies for Circulating Tumor DNA Detection May Reveal Occult Hematologic Malignancies in Patients With Solid Tumors

PURPOSE

High-risk clonal hematopoiesis (CH) is frequently incidentally found in patients with solid tumors undergoing plasma cell-free DNA sequencing. Here, we aimed to determine if the incidental detection of high-risk CH by liquid biopsy may reveal occult hematologic malignancies in patients with solid tumors.

MATERIALS AND METHODS

Adult patients with advanced solid cancers enrolled in the Gustave Roussy Cancer Profiling study (ClinicalTrials.gov identifier: NCT04932525) underwent at least one liquid biopsy (FoundationOne Liquid CDx). Molecular reports were discussed within the Gustave Roussy Molecular Tumor Board (MTB). Potential CH alterations were observed, and patients referred to hematology consultation in the case of pathogenic mutations in JAK2, MPL, or MYD88, irrespective of the variant allele frequency (VAF), or in DNMT3A, TET2, ASXL1, IDH1, IDH2, SF3B1, or U2AF1 with VAF ≥ 10%, while also considering patient cancer-related prognosis. TP53 mutations were discussed case-by-case.

RESULTS

Between March and October 2021, 1,416 patients were included. One hundred ten patients (7.7%) carried at least one high-risk CH mutation: DNMT3A (n = 32), JAK2 (n = 28), TET2 (n = 19), ASXL1 (n = 18), SF3B1 (n = 5), IDH1 (n = 4), IDH2 (n = 3), MPL (n = 3), and U2AF1 (n = 2). The MTB advised for hematologic consultation in 45 patients. Overall, 9 patients of 18 actually addressed had confirmed hematologic malignancies that were occult in six patients: two patients had myelodysplastic syndrome, two essential thrombocythemia, one a marginal lymphoma, and one a Waldenström macroglobulinemia. The other three patients were already followed up in hematology.

CONCLUSION

The incidental findings of high-risk CH through liquid biopsy may trigger diagnostic hematologic tests and reveal an occult hematologic malignancy. Patients should have a multidisciplinary case-by-case evaluation.

Abstract PD8-02: Trastuzumab deruxtecan (T-DXd) for advanced breast cancer patients (ABC), regardless HER2 status: A phase II study with biomarkers analysis (DAISY)

Background: The HER2-targeted antibody-drug conjugate (ADC) trastuzumab deruxtecan (T-DXd) demonstrated efficacy in heavily pretreated HER2-over- and HER2-low expressing ABC (1, 2). We aimed to assess the activity of T-DXd in HER2-over-, HER2-low and HER2-nul expressing ABC, to describe the drug mechanisms of action in the 3 cohorts and to identify biomarkers associated to drug response or resistance. Study Description: DAISY is a multicenter, open-label phase II trial designed to assess the efficacy of single agent T-DXd at 5.4 mg/kg dose in ABC with extensive biomarkers analysis. Three cohorts of patients were included: Cohort 1 (HER2 over-expressing: HER2 3+ on immunohistochemistry (IHC) or HER2 IHC2+/in situ hybridization [ISH]+), Cohort 2 (HER2 low-expressing: IHC1+ or IHC2+/ISH-) and cohort 3 (HER2-nul: IHC0+). Biopsy of metastatic sites was performed: at baseline, on treatment (mandatory for cohort 1, optional for cohort 2/3) and at tumor progression; blood samples for ctDNA were collected at baseline. The primary endpoint was the Best Overall Response (BOR) in each cohort, according to the investigator assessment. Secondary endpoints were BOR by central assessment, clinical benefit rate, duration of response (DOR), progression-free (PFS), overall survival (OS) and safety. Results:185 women and 1 man were enrolled between November 2019 and March 2021. Among the patients enrolled in the safety population (see Table 1), median (range) age was 55 (24-82) years, all received at least one prior line of therapy and 12 patients were TN. Table 2 shows investigator-reported T-Dxd activity in the 3 cohorts at a median follow-up of 10.1 months [95%CI: 9.2-11.1]. A total of 170 patients (95%) had at least one treatment-related toxicity. Key grade ≥3 treatment-related toxicities included neutropenia (10.6% of patients), fatigue (5.6%), leucopenia (4.5%), vomiting (4.5%) and anemia (3.4%). A total of 4 patients had drug-related interstitial lung disease or pneumonitis (grade 1 in 3 patients and grade 2 in 1 patient), 11 patients discontinued treatment due to treatment-related adverse events. No drug-related deaths occurred. Conclusions: T-DXd showed clinically meaningful activity in patients with HER2-overexpressing ABC and interestingly also in those with HER2low and HER2-nul ABC. Safety profile was consistent with previous reports. 1.Modi S et al N Engl J Med 2020 2.Mosi S et al J Clin Oncol 2020

Table 1.Analysis populationsTotalCohort 1 (HER2 over-expressing)Cohort 2 (HER2 low-expressing)Cohort 3 (HER2 non-detected)Enrolled population186727440Safety population*179687338 (including 12 TN)Full analysis Set**176687236TN: Triple Negative. *: safety population = enrolled population except 7 patients who did not receive at least one dose of study drug. **: Full Analysis Set = safety population except 3 patients (2 who did not have a valid first post-baseline assessment of disease status or who did not have progressive disease and 1 who did not have at least one radiologically measurable lesion according to RECIST v1.1)

Table 2.T-DXd activity in the three cohorts according to investigator assessmentTotalCohort 1Cohort 2Cohort 3BOR confirmedn/N82/176 (46.6%)47/68 (69.1%)24/72 (33.3%)11/36 (30.6%)[95%CI][39.1; 54.2][56.7; 79.8][22.7; 45.4]16.3; 48.1]Median DORmonths7.69.97.66.8[95%CI][6.2; 9.7][5.4; NR][4.4; 8.7][2.8; 8.3]Median PFSmonths6.911.16.74.2[95%CI][6.7; 8.7][8.4; NR][4.6; 8.5][2.1; 6.9]NR: Not Reached

Citation Format: Véronique Diéras, Elise Deluche, Amélie Lusque, Barbara Pistilli, Thomas Bachelot, Jean-Yves Pierga, Frédéric Viret, Christelle Levy, Laura Salabert, Fanny Le Du, Florence Dalenc, Christelle Jouannaud, Laurence Venat-Bouvet, Jean-Philippe Jacquin, Xavier Durando, Thierry Petit, Céline Mahier - Aït Oukhatar, Thomas Filleron, Maria Fernanda Mosele, Magali Lacroix-Triki, Agnès Ducoulombier, Fabrice André. Trastuzumab deruxtecan (T-DXd) for advanced breast cancer patients (ABC), regardless HER2 status: A phase II study with biomarkers analysis (DAISY) [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 PD8-02.