Diagnosed With Cancer? Why You Should Consider Genetic Testing, and How to Ask for It

By Amanda Shrewsbury, MS, CGC

Many people assume that if genetic testing applied to their cancer diagnosis, someone on their care team would have already brought it up, but the reality is that genetic testing is sometimes not offered at the time of a diagnosis, even when it's recommended by current guidelines.

This gap matters more than most people realize. Genetic testing after a cancer diagnosis is not only about understanding hereditary risk for the future. It can sometimes directly shape treatment decisions, influence surgical choices, and provide information that protects the health of an entire family. When genetic testing is not done, an opportunity that could change the course of care can be missed.

This post is written for anyone who has recently been diagnosed with cancer, or who loves someone who has. It explains why genetic testing matters after a diagnosis, why it is sometimes not offered even when it should be, how current guidelines have expanded to include far more people, and how to advocate for yourself so that this important step does not get overlooked.

Why genetic testing matters after a cancer diagnosis

When most people think about genetic testing for cancer, they think about prevention. But for someone who has already been diagnosed, genetic testing can serve additional and immediate purposes.

It can shape your treatment. Certain genetic test results open the door to specific therapies. For example, cancers associated with BRCA1, BRCA2, and PALB2 variants may respond to a class of drugs called PARP inhibitors, which are used in certain breast, ovarian, pancreatic, and prostate cancers. These drugs work by exploiting a weakness in cancer cells that cannot repair their DNA properly. Similarly, cancers associated with Lynch syndrome can be what is called mismatch repair deficient, and these tumors frequently respond well to immunotherapy. A genetic test result can be the piece of information that points toward one of these targeted treatment paths.

It can inform surgical and management decisions. Knowing that a cancer is hereditary can change decisions about surgery, because a person with a hereditary predisposition may face an elevated risk of a second, separate cancer in the future. For example, if someone diagnosed with breast cancer tests positive for a variant that increases the risk of contralateral breast cancer (a second, new breast cancer in the other breast in the future), they may want to consider a more extensive surgery, such as a bilateral mastectomy, rather than a lumpectomy. That knowledge can influence the scope of surgery a person chooses and the screening they pursue afterward.

It can protect your family. A hereditary cancer result is rarely just about one person. It can be life-changing information for relatives, who may have inherited the same variant and who could benefit from earlier screening and prevention. This process, called cascade testing, is one of the most powerful tools in hereditary cancer care. Our post on cascade testing explains how it works.

Why testing is sometimes not offered, even when it should be

If genetic testing is this valuable, why is the option to test sometimes not discussed at diagnosis? The reasons are understandable, and they are not usually about any single person failing to do their job.

Oncology visits after a new diagnosis are full. There is an enormous amount to cover in a short time, and the immediate focus is often on staging and starting treatment. Genetic testing can get crowded out. On top of that, genetic testing guidelines have expanded rapidly in recent years, and awareness of the newest recommendations is not always uniform across every practice. Many clinics also do not have a genetic counselor on site, which can make it harder to fold testing into the flow of care. And historically, testing was often reserved for people with a striking family history, an approach that current guidelines have moved well beyond.

None of this is a reason for blame. It is, however, a reason to understand the current guidelines yourself, so that you can raise the topic if it has not come up.

Guidelines now recommend testing for far more people than before

The bar for who should be offered genetic testing after a cancer diagnosis has moved significantly, and in most cases it has moved toward testing more people, not fewer. Here are some of the most important recent expansions.

Breast cancer. The American Society of Clinical Oncology (ASCO) and the Society of Surgical Oncology (SSO) now recommend that everyone diagnosed with breast cancer at age 65 or younger be offered genetic testing. This 2024 recommendation represents a major expansion, moving away from older approaches that relied heavily on family history or younger age cutoffs.

Colorectal, endometrial, and gastric cancer. The National Comprehensive Cancer Network (NCCN), in its 2026 guidelines, now recommends genetic testing to evaluate for Lynch syndrome for everyone diagnosed with colorectal, endometrial, or gastric cancer, regardless of age at diagnosis. It is worth noting that this is a category 2B recommendation, meaning it is considered appropriate by the panel but is based on lower-level evidence without uniform consensus. Even so, it reflects a clear direction: these cancers can be hereditary at any age, and testing is increasingly recommended across the board.

Pancreatic cancer. NCCN recommends genetic testing for everyone diagnosed with pancreatic cancer, regardless of family history, reflecting how frequently a hereditary factor is involved. Our post on pancreatic cancer and genetic testing covers this in more detail.

Prostate cancer. NCCN recommends germline genetic testing for men with high-risk, very-high-risk, regional, or metastatic prostate cancer, regardless of family history.

The through-line across all of these is the same. Many people diagnosed with cancer today qualify for genetic testing under current guidelines, even without a dramatic family history, and the trend continues to move toward broader testing.

That said, not every cancer has a strong hereditary link, and a genetic counselor can tell you whether testing is likely to be informative for your specific diagnosis.

A note on the kind of testing that is done

When genetic testing is pursued after a diagnosis, it is generally done as a multigene panel, which examines many cancer-related genes at once, rather than testing a single gene in isolation. This matters because hereditary cancer risk can involve a wide range of genes. A panel gives a fuller picture, and it is the approach most consistent with how hereditary cancer is understood today. Our post on the cancers that can be hereditary shows just how many genes and cancers can be involved.

What genetic testing results can tell you

A genetic test after a diagnosis generally returns one of a few kinds of results. A positive result means a pathogenic variant was found, which may inform treatment, surgery, and family testing. A negative result means no variant was found, though depending on the situation this may not fully rule out hereditary risk. A variant of uncertain significance (VUS) means a change was found whose meaning is not yet known, and medical decisions are not based on a VUS alone. A genetic counselor helps interpret whatever the result turns out to be. Our post on understanding a variant of uncertain significance explains that result in more detail.

How to advocate for yourself

If you have been diagnosed with cancer and genetic testing has not come up, you do not have to wait for someone to offer it. Here are concrete ways to raise it.

Ask directly. A simple question works: "Based on current guidelines, do I qualify for genetic testing?" You can also ask specifically whether the NCCN or ASCO guidelines for your cancer type recommend testing in your situation.

Ask about a referral to a genetic counselor. A genetic counselor is the specialist who can review your personal and family history, determine whether testing is appropriate, recommend the right panel, and interpret the results. You can request a referral, and you can also seek genetic counseling independently rather than waiting for one to be arranged.

Frame it around treatment, not just family history. Because a genetic result can affect treatment options, mentioning that can sometimes reframe the urgency of testing. This is not only about future prevention; it can be relevant to the care you are receiving right now.

Pay attention to timing. Genetic testing is most useful when it can still inform decisions, so raising it sooner rather than later is worthwhile. If a result could influence treatment or surgical choices, having it in hand earlier is better.

What to do next

If you or someone you love has been diagnosed with cancer and genetic testing has not been discussed, a genetic counselor can help. A genetic counselor can review your situation, tell you whether you qualify under current guidelines, recommend appropriate testing, and coordinate with your care team so that the results are put to use.

A few resources from our blog that may help:

Being newly diagnosed with cancer is one of the most overwhelming experiences a person can face, and asking about genetic testing may be the last thing on your mind, but it is a question worth raising, because the answer can shape your treatment, your future, and the health of the people you love.

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Talk with a ClearPath Genetic Counselor

If you have been diagnosed with cancer and want to know whether genetic testing is right for you, we can help you understand your options and advocate for your care.

Have a Question? Text or call us at (720) 799-0730 or email us at hello@clearpathgenetics.com.

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References

Bedrosian, I., Somerfield, M. R., Achatz, M. I., Boughey, J. C., Curigliano, G., Friedman, S., Kohlmann, W., Kurian, A. W., Laronga, C., Lynce, F., Norquist, B. S., Plichta, J. K., Rodriguez, P., Shah, P. D., Tung, N., Yao, K., & Robson, M. E. (2024). Germline testing in patients with breast cancer: ASCO–Society of Surgical Oncology guideline. Journal of Clinical Oncology, 42(5), 584–604.

National Comprehensive Cancer Network. (2026). NCCN clinical practice guidelines in oncology: Genetic/familial high-risk assessment — Colorectal, endometrial, and gastric (Version 1.2026). https://www.nccn.org/

National Comprehensive Cancer Network. (2026). NCCN clinical practice guidelines in oncology: Genetic/familial high-risk assessment — Breast, ovarian, and pancreatic (Version 3.2026). https://www.nccn.org/

National Comprehensive Cancer Network. (2025). NCCN clinical practice guidelines in oncology: Prostate cancer (Version 1.2025). https://www.nccn.org/

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This blog post is for educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always seek the advice of your physician, genetic counselor, or other qualified healthcare provider with any questions you may have regarding a medical condition or your individual health needs.