Who Should Get Genetic Testing After a Cancer Diagnosis?

Limiting inherited genetic testing to younger people with cancer would have missed most of those who carry a cancer-risk gene change, according to a study of 39,184 people with solid tumors published Oct. 8, 2026, in Cancer Discovery. Researchers at Memorial Sloan Kettering Cancer Center (MSK) in New York found that if testing had been offered only to people diagnosed before age 50, 4,601 carriers, or 72% of all carriers in the study, would have gone unidentified.

What Is Inherited (Germline) Genetic Testing?

Germline genetic testing looks for gene changes you were born with and can pass to your children. These are different from changes found only in the tumor itself. A harmful inherited change is called a pathogenic variant. Well-known examples include changes in the BRCA1 and BRCA2 genes and in the genes linked to Lynch syndrome, an inherited condition that raises the risk of colorectal, uterine and other cancers.

The test usually uses a blood or saliva sample.

What the Study Looked At

All 39,184 patients, who had 32 different types of solid tumors, were tested at MSK regardless of age or family history. Their average age was 59. The team used MSK-IMPACT, a test that compares tumor DNA with normal DNA from blood or saliva, and checked for inherited variants across 94 genes.

For each cancer type, researchers grouped patients as early-onset, average-onset or late-onset, based on how their age at diagnosis compared with the typical age for that cancer. They also asked how many carriers a strict under-50 rule would have missed.

What It Found

• About 1 in 6 patients (16.3%) carried at least one inherited pathogenic variant.
• Carriers were found in every age group: 18.4% of early-onset patients, 15.6% of average-onset patients and 12.3% of late-onset patients.
• Variants in high-penetrance genes, which raise cancer risk the most, were found in 9.1% of early-onset, 5.5% of average-onset and 2.6% of late-onset patients. Moderate-penetrance variants were found in 3.3%, 3.4% and 2.5%, respectively.
• About 9.7% of all patients carried a high- or moderate-penetrance variant.

“Hereditary cancer can occur at any age,” said co-corresponding author Dr. Luis A. Diaz Jr., head of MSK’s Division of Solid Tumor Oncology, in a statement from the AACR.

Why Testing Matters for Treatment and for Your Family

An inherited finding can shape care. Tumors in people with BRCA variants often respond to a class of drugs called PARP inhibitors, and people with Lynch syndrome are more likely to respond to immune checkpoint inhibitors, a type of immunotherapy, MSK noted. Carriers can also be offered closer screening for other cancers.

Results matter for relatives, too. When someone tests positive, parents, siblings and children can be offered testing for that same variant, a process called cascade testing. Co-corresponding author Dr. Zsofia K. Stadler called cascade testing “one of the most underused opportunities in cancer prevention.”

What Current Guidelines Say

This study does not change guidelines on its own. Today, recommendations depend on cancer type. A guideline from the American Society of Clinical Oncology (ASCO) and the Society of Surgical Oncology published in January 2024 says BRCA1/2 testing should be offered to everyone newly diagnosed with breast cancer at age 65 or younger, and considered for older patients who meet certain criteria, such as being a candidate for a PARP inhibitor or having triple-negative breast cancer. Since 2019, the National Comprehensive Cancer Network (NCCN) has recommended germline testing for everyone with pancreatic adenocarcinoma. An ASCO guideline published in May 2024 says all adults with cancer should have a family history taken and that multigene panel testing should be offered when more than one gene is relevant. CURE has also covered what patients with breast cancer can learn from germline testing and the case for universal testing in colon cancer.

Insurance and Cost Basics

Coverage usually depends on whether you meet guideline criteria for your cancer type, so ask your care team or a genetic counselor to check with your insurer before testing. Relatives are typically covered under their own insurance. The federal Genetic Information Nondiscrimination Act (GINA) bars health insurers and most employers from discriminating based on genetic information, but it does not cover life, disability or long-term care insurance, and its job protections generally do not apply to employers with fewer than 15 workers.

What’s Still Unknown

This was an observational analysis from a single cancer center, so it shows how often carriers appear at different ages, not whether testing everyone improves survival. Patients treated at a large referral center may differ from the general population, and the study did not include blood cancers. Not every variant found carries the same level of risk or leads to a change in treatment.

Questions to Ask Your Care Team

• Do I qualify for inherited (germline) genetic testing, and would my results change my treatment?
• Was the testing on my tumor also checked against my normal DNA, or do I need a separate test?
• Can I meet with a genetic counselor before and after testing?
• Will my insurance cover the test, and how should I share results with my relatives?

References

1. "Universal Germline Genetic Testing After a Cancer Diagnosis" (full title to confirm). Stadler ZK, Diaz LA Jr, et al. Cancer Discovery. Oct. 8, 2026.
2. "Study Suggests All Patients Diagnosed With Cancer, Regardless of Age, Should Receive Genetic Testing." American Association for Cancer Research. Oct. 8, 2026.
3. "Study Suggests Every Cancer Patient Should Be Tested for Inherited Cancer Mutations." Memorial Sloan Kettering Cancer Center. Oct. 8, 2026.
4. "Germline Testing in Patients With Breast Cancer: ASCO-Society of Surgical Oncology Guideline." Bedrosian I, et al. Journal of Clinical Oncology. Jan. 4, 2024.
5. "Selection of Germline Genetic Testing Panels in Patients With Cancer: ASCO Guideline." Tung N, et al. Journal of Clinical Oncology. May 17, 2024.
6. "NCCN Clinical Practice Guidelines in Oncology: Pancreatic Adenocarcinoma." National Comprehensive Cancer Network. 2019 update and later versions.
7. "Genetic Information Nondiscrimination Act of 2008." U.S. Congress. May 21, 2008