Facilitating shared decision making about somatic tumor testing

Large panel genomic tumor testing (also called somatic testing) is a promising technology that has the potential to improve care for many patients. However, this testing is not the best choice for all patients and some who have testing will not benefit from the results. Shared decision making can help patients make well-informed decisions that are consistent with their preferences and values.

Discussing the option of genomic tumor testing with cancer patients can be complex as this discussion often considers disease progression and current therapeutic options as well as the patient’s readiness to investigate a change in therapy and possibly, research participation.

The goal of this resource is to support clinicians when communicating with patients about the process, benefits, risks, and limitations of genomic tumor testing so they can make informed decisions about whether to undergo testing.

Key messages for communicating about genomic tumor testing

(1) Overview of testing

The primary goal of genomic tumor testing is to identify possible personalized (targeted) treatments for a patient’s cancer type. Genomic tumor testing is used to find DNA changes, or variants, that exist in cancer cells. Some of these variants may play a role in how the cancer grows, spreads, and responds to treatment. Therefore, genomic tumor test results can sometimes help clinicians choose the right medicines to treat a person’s cancer.

Genomic tumor testing (versus germline testing)

  • The goal of genomic tumor testing is to identify genetic variants that are present in tumor cells (somatic).
  • Its primary purpose is not to assess for inherited variants that can be passed from parent to child (germline); however, genomic tumor testing can sometimes identify an inherited variant.
  • Patients with possible inherited variants should receive genetic counseling and possibly germline genetic testing.


  • Access to testing. There are different options for obtaining genomic tumor testing. Testing can be ordered through a commercial lab, and there may be options for obtaining testing through research protocols. Each of these options has advantages and disadvantages--including access to experts, research participation, cost, and time--that should be discussed with the patient to determine the best choice for them.
  • Sample requirements. Discuss the sample requirements for testing, including whether sufficient tumor tissue exists or if a repeat biopsy is necessary. If a liquid biopsy is considered a blood sample is required rather than a tumor sample.
  • Turn-around time. Patients often have questions about the turn-around time for receiving results. It can take up to 2-3 weeks once the lab receives the sample to get results back from tumor testing, depending on a variety of factors, including sample selection and processing. The anticipated timeline should be discussed with the patient in terms of the potential benefits of a newly identified targeted treatment versus the need to potentially delay treatment decision making pending receipt of results.
(2) Benefits of testing

The purpose of tumor testing is to identify possible personalized (targeted) treatments for the patient’s specific cancer. The results of genomic tumor testing may provide information on how a patient’s cancer is expected to act and may help determine how to treat the cancer. Tumor testing may identify treatments that may not be apparent based on existing pathology reports. In some situations, tumor testing can also provide information about prognosis.

Patients may ask how likely it is that tumor testing will identify a targeted treatment. This is a new area of medicine with varying rates of utility reported in different studies. Not all patients who have a variant identified will change management based on test results.

(3) Uncertainties

There are limited data supporting the therapeutic benefit of targeted treatments. Patients may receive a result that is uninformative because there is not a clear recommendation for treatment based on the results. It is important that clinicians discuss this limitation with patients to set realistic expectations.

(4) Potential harms or disadvantages

In general, there are no physical risks of testing (other than those associated with a new biopsy, if indicated). However, due to the limitations discussed above, there is the risk of unrealistic expectations from the patient, resulting in disappointment, anxiety or distress after receiving tumor testing results. This is because the result may:

  • Not be helpful in identifying new treatments
  • Identify genetic variants that have uncertain significance for treatment
  • Identify genetic variants that do not have an associated treatment
  • Show that the patient is eligible for a medicine that their insurance does not cover
  • Show that the patient is eligible for a clinical trial that the patient cannot participate in, due to eligibility criteria or distant location.

Targeted treatments may improve patient outcomes but are unlikely to cure cancer for most patients. Some patients may not respond at all or may respond favorably for a period of time before the tumor develops resistance and stops responding to the treatment.

Tumor testing could also identify a potential inherited genetic variant. In this case, additional evaluation and testing is often indicated. If an inherited genetic variant is found, the patient’s relatives may be at increased risk for cancer or other disease. While some patients may be distressed to learn this information, others may see this as a benefit of testing.

Important patient values in decision making

The personal values and experiences of cancer patients, and those of their family members, may influence decisions about tumor testing.

  • Effects on survival. For some people, pursuing all lines of potential treatment is worthwhile, no matter the time, cost, and emotional burden.
  • Effects on quality of life. The likelihood that genomic testing and a new targeted treatment will improve or worsen their current quality of life is an important consideration for some patients.
  • Current health. An individual in poor health with several comorbidities may not be a candidate for targeted treatments and/or a clinical trial, so testing is less likely to yield useful information for that patient. Additionally, some patients who are physically and emotionally fatigued may be reluctant to initiate a new evaluation with uncertain benefit.
  • Interest in and ability to participate in clinical trials. Genomic tumor testing may identify a targeted treatment available through a clinical trial. Patients have a positive view of research participation or may see this as a less desirable treatment option.
  • Cost. Patients may weigh insurance coverage and the cost of testing and/or downstream targeted therapies in their decisions about testing.
  • Benefiting others through research. Regardless of their desire to undergo tumor testing, patients may be motivated to participate in a research initiative like MCGI. Patients with advanced cancer often perceive participation in research as beneficial to the future of cancer care and value helping others.

Facilitating shared decision making

Communicating with patients about the decision to undergo genomic tumor testing is much like conversations in other areas of cancer care. Patient motivation, expectations and concerns, as well as psychological response to the cancer diagnosis and its treatment, will all play a role in decision making about genomic tumor testing. The provider’s counseling skills can be an effective facilitator of effective patient decision making. It can be helpful to follow the SHARE framework for shared decision making:

Step 1: Seek your patient’s engagement in the discussion about genomic tumor testing.

Step 2: Help your patient explore and compare options about whether or not to test and/or which test is best for the patient.

Step 3: Assess your patient's values and preferences.

Step 4: Reach a decision with your patient.

Step 5: Evaluate your patient's decision.

Learn more

Talking to Cancer Patients about Genetic Testing This video from MedPage today is part of the ASCO Clinical Pearls series.

The SHARE Approach – Essential Steps of Share DecisionmakingThis Guide from AHRQ presents a five-step process for shared decision making that can be applied across health care.

Exploring Cancer Biomarker Testing(CME | CNE). Learn about benefits, limitations, and challenges of using cancer biomarker testing.

Choosing the Best Genomic Tumor Test (CME | CNE). Learn about the benefits and limitations of different genomic tumor test options for patients with cancer and how to determine the best test for each patient.


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This resource was developed as part of the Maine Cancer Genomics Initiative (MCGI) and is supported by The Harold Alfond Foundation and The Jackson Laboratory.

Reviewed May 2023