The study involved 11,974 patients with various tumor types. All the patients underwent germline genetic testing from 2015 to 2019 at the Memorial Sloan Kettering Cancer Center (MSKCC) in New York, using the next-generation sequencing panel MSK-IMPACT.
This testing showed that 17.1% of patients had variants in cancer predisposition genes, and 7.1%-8.6% had variants that could potentially be targeted.
“Of course, these numbers are not static,” commented lead author Zsofia K. Stadler, MD, a medical oncologist at MSKCC. “And with the emergence of novel targeted treatments with new FDA indications, the therapeutic actionability of germline variants is likely to increase over time.
“Our study demonstrates the first comprehensive assessment of the clinical utility of germline alterations for therapeutic actionability in a population of patients with advanced cancer,” she added.
Dr. Stadler presentedduring a virtual scientific program of the American Society of Clinical Oncology 2020.
Testing for somatic mutations is evolving as the standard of care in many cancer types, and somatic genomic testing is rapidly becoming an integral part of the regimen for patients with advanced disease. Some studies suggest that 9%-11% of patients harbor actionable genetic alterations, as determined on the basis of tumor profiling.
“The take-home message from this is that now, more than ever before, germline testing is indicated for the selection of cancer treatment,” said Erin Wysong Hofstatter, MD, from Yale University, New Haven, Conn., in a Highlights of the Day session.
An emerging indication for germline testing is the selection of treatment in the advanced setting, she noted. “And it is important to know your test. Remember that tumor sequencing is not a substitute for comprehensive germline testing.”
Implications in cancer treatment
For their study, Dr. Stadler and colleagues reviewed the medical records of patients with likely pathogenic/pathogenic germline (LP/P) alterations in genes that had known therapeutic targets so as to identify germline-targeted treatment either in a clinical or research setting.
“Since 2015, patients undergoing MSK-IMPACT may also choose to provide additional consent for secondary germline genetic analysis, wherein up to 88 genes known to be associated with cancer predisposition are analyzed,” she said. “Likely pathogenic and pathogenic germline alterations identified are disclosed to the patient and treating physician via the Clinical Genetic Service.”
A total of 2043 (17.1%) patients who harbored LP/P variants in a cancer predisposition gene were identified. Of these, 11% of patients harbored pathogenic alterations in high or moderate penetrance cancer predisposition genes. When the analysis was limited to genes with targeted therapeutic actionability, or what the authors defined as tier 1 and tier 2 genes, 7.1% of patients (n = 849) harbored a targetable pathogenic germline alteration.
BRCA alterations accounted for half (52%) of the findings, and 20% were associated with Lynch syndrome.
The tier 2 genes, which included PALB2, ATM, RAD51C, and RAD51D, accounted for about a quarter of the findings. Dr. Hofstatter noted that, using strict criteria, 7.1% of patients (n = 849) were found to harbor a pathogenic alteration and a targetable gene. Using less stringent criteria, additional tier 3 genes and additional genes associated with DNA homologous recombination repair brought the number up to 8.6% (n = 1,003).