ESR1 Mutation Analysis, Next-Generation Sequencing, Tumor

Casandra

Casandra Test Code MC17667Version 1 (DRAFT)

Performing Lab

Lab Mayo Clinic LabLab Test ID ESR1TCPT Codes 81479, 88381

ESR1 Mutation Analysis, Next-Generation Sequencing, Tumor

Clinical Use

Use

This test assists in the clinical management of patients with metastatic breast cancer by identifying tumors with evolving resistance to endocrine therapy. It helps in stratifying the prognosis of metastatic breast cancer. The test evaluates somatic mutations within the ESR1 gene to provide insights into the potential mechanisms leading to resistance against endocrine treatments such as selective estrogen receptor modulators and degraders, and aromatase inhibitors. By identifying mutations in the ligand-binding domain of ESR1, the assay aids in determining patient eligibility for targeted therapies like elacestrant (Orserdu), which is indicated for specific patient groups with ESR1 mutations.

Special Instructions

For the assay to be performed, a pathology report containing patient name, block number, tissue collection date, and source of the tissue must accompany the specimen. Specimen fixation must be in 10% neutral buffered formalin. Preferably, submit three specimens if available, or at least two, ensuring tumor area and percentage of tumor nuclei are adequate for testing. Unstained slides will not be returned. Test forms must be completed and sent with the specimen if not ordering electronically.

Limitations

The test cannot differentiate between somatic and germline alterations. A negative result does not preclude the presence of a variant that may be below detection limits or is unaddressed by this assay. Multiexon deletions and duplications are not detected, nor are genomic copy number variants. Analytical sensitivity for sequence-reportable alterations requires at least a 5% mutant allele frequency. Reliable results depend on proper specimen collection and processing, avoiding decalcified tissues. Additional testing may be required to clarify results or if there's a potential hereditary risk.

Test Details

New York Approved