Abstract PO2-12-08: Increased burden of genetic variants in idiopathic cardiomyopathy genes is associated with cancer therapy-related cardiomyopathy
Authors: Norton Nadine , Nguyen Thien , Reddy Joseph , Harvey Jinky , Weidner Morgan , Arnold Amanda , Evans Lily , Vallow Laura , Advani Pooja 
Published: May 2024

Abstract
Background: Breast cancer (BC) patients are at significant risk of therapy-related cardiotoxicity, but prediction of which patients will experience cardiotoxicity and the severity of the outcome are lacking. We hypothesized that germline genetic variants are potential risk factors for cancer treatment-related cardiomyopathy (CTRC) and in this study, we focused on rare non-synonymous variants within 57 genes deemed causative of familial and sporadic forms of idiopathic cardiomyopathies.
Methods: We developed a clinical database and biorepository for patients receiving any potentially cardiotoxic cancer therapy at Mayo Clinic Florida. Enrollment is ongoing and includes consent to access external records. Patient data is extracted from records at baseline, completion of treatment and then once per year. The clinical database includes the following datasets: demographics, pathology, chemotherapy, radiation, echocardiography, cardiac MRI, PET/CT scan, blood pressure, BMI, labs, treatment complications. Treatment complications includes pre-existing conditions (smoking, alcohol and drug use history, hypertension, diabetes, coronary artery disease, hyperlipidemia, prior stroke or myocardial infarction, peripheral vascular disease, renal failure); cardiac medications at baseline; cardiac side-effects; time to cardiotoxicity; cardiotoxicity interventions and outcomes.
Exome sequencing was performed by the Mayo Clinic NGS core on the first 86 patients in the registry, average of ~120x read depth following Illumina’s standard protocol for the NovaSeq 6000 and S4 flow cell. Genomic variants were extracted for 57 genes known to be causative of dilated, hypertrophic and arrhythmogenic right ventricular cardiomyopathies and channelopathies. Putative risk variants in known cardiomyopathy genes were defined as non-synonymous variants with a frequency of &lt; 0.0004 in the GnomAD database. We compared the number of patients with putative risk variants in those groups with and without CTRC.
Results: 84/86 patients had BC diagnosis. Key characteristics are described in the table below. 60/86 (70%) patients had at least one putative risk variant in one of 31 genes (there were no risk variants identified in 27/57 genes). The average number of putative risk variants per patient within the CTRC group was higher than that observed in patients without CTRC (2.06 vs 1.62). Post-hoc analysis suggested this difference is largely from patients with &gt;2 risk variants in the group who experienced CTRC (N=7/17, 41%) compared to those who did not (N=14/69, 20%), p=0.023.
Conclusions: Rare missense variants in the causative genes of idiopathic cardiomyopathies are potential risk factors for CTRC and risk may be increased in patients with a higher burden of variants. Analysis of the genetic data from patients that continue to be accrued in this study, including effects of additional clinical risk factors will be undertaken to improve prediction of cardiotoxicity.
Table 1
Distribution of putative cardiomyopathy genetic variants in 86 cancer patients with and without treatment-related cardiomyopathy, separated by treatment regimen
Citation Format: Nadine Norton, Thien Nguyen, Joseph Reddy, Jinky Harvey, Morgan Weidner, Amanda Arnold, Lily Evans, Laura Vallow, Pooja Advani. Increased burden of genetic variants in idiopathic cardiomyopathy genes is associated with cancer therapy-related cardiomyopathy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-12-08.