Somatic (Tumor) Testing

Many companies now provide genetic testing of tumors, looking for somatic mutations with the aim of providing clinicians with information on their patient’s prognosis, alternative therapeutic agents, or potential clinical trials, particularly if all other options for treatment of the tumor have been explored. These tests usually involve sending a sample of the patient’s tumor and sometimes also a blood sample to assess the patient’s germline genetics, as well.

If the testing lab does ask for a blood sample, it is important to know if this information will be used only as a filter to assess for true somatic variants or if the lab will also report underlying hereditary cancer predisposition syndromes identified.

When considering or reviewing somatic testing results, it’s important to keep the following things in mind:

  • Somatic testing, while it is a form of genetic testing, is different from traditional germline testing assessing for underlying hereditary cancer predisposition syndromes.
  • These tests are not designed to report out these kinds of germline genetic changes.
  • Just because there is a BRCA1 gene mutation found on a somatic test mutation report does not mean that the patient has Hereditary Breast and Ovarian Cancer syndrome (HBOC).
  • Conversely, in a patient with a strong personal and family history of breast and ovarian cancer, a clinician should not assume that the patient is “negative” for a BRCA gene mutation just because one is not reported on a somatic test report.
  • All individuals undergoing somatic tumor testing should be assessed for likelihood for an underlying hereditary cancer predisposition syndrome and be referred for separate appropriate germline genetic testing, if indicated.
  • Lab quality is very important. The quality of the data returned depends highly on the quality of tumor sample provided and the quality of the assays the lab uses.

It can be challenging to determine which “actionable” variants reported on a somatic test report may be most beneficial for the patient. The American College of Medical Genetics (ACMG), American Society of Clinical Oncology (ASCO), and Association for Molecular Pathology (AMP) all recommend a multidisciplinary approach to review of somatic test reports with the ordering clinician, bioinformaticists, molecular pathologists, and genetic counselors to “bridge the inevitable gap in knowledge between those closely involved with genomic data interpretation and health care providers who would be hard pressed to keep up with new developments but who need to integrate this information into their medical practice” (AMP, 2012).

UT Southwestern has developed a Molecular Tumor Board that meets monthly so that these cases and somatic test reports can be presented and reviewed with a multidisciplinary approach. For the date, time, and location of the next meeting, or for other questions, please contact TumorGenomics@utsouthwestern.edu.