What is Genomic Testing for Prostate Cancer?
Men with high-risk localized prostate cancer require intensive treatment of their cancer in order to diminish the risk of dying of prostate cancer. Over the last five to 10 years, genomic testing has evolved to try and “personalize” the treatment of prostate cancer.
Genomic testing takes on two forms:
(1) looking at the genes you were born with, that are found in every cell in your body (i.e., your DNA, or “what makes you who you are”), or
(2) looking at cancer genes in the prostate tumor itself. The first type of testing is called “germline testing” and the second type is called “somatic testing.” Germline testing is typically done from a blood test or a saliva sample, whereas somatic testing is done from biopsy tissue from the prostate or from one of the sites that prostate cancer has spread to (i.e., the bones, liver, lungs, lymph nodes). One of the most common germline genomic tests is the FoundationOne Liquid CDX test, which is an FDA-approved test that analyzes genes from a simple blood test, in addition to being the only approved blood test to analyze over 300 genes.
Genomic testing helps doctors see how DNA and genes work within the cell and can suggest a path to better treat your cancer. Furthermore, genomic testing may be able to answer other questions, such as:
- Will your cancer grow slowly or will it get worse quickly?
- Is your cancer likely to spread?
- What types of treatment should we use to treat your prostate cancer?
In other articles, we discuss how genomics makes up the basis for pre- and post-prostate biopsy biomarkers. In this article, we focus on genomic testing that identifies certain genes that may provide further information for cancer aggressiveness and for guiding treatment. It is important to understand who is most likely to benefit from either germline or somatic genomic testing. The National Comprehensive Cancer Network (NCCN) suggests that all of the following men with prostate cancer should be considered for genomic testing:
- A family history of prostate cancer
- High and very high risk localized prostate cancer
- Locally advanced and metastatic prostate cancer
- Ashkenazi Jewish ancestry
- Intraductal or cribriform (particularly aggressive cells on microscopic examination on prostate biopsy tissue) prostate cancer
Furthermore, it is important to understand how genomic testing may guide treatment plans. For men who have had surgery, it may help with understanding their risk of recurrence in the future. This may be important to guide the early use of subsequent treatments (like radiation or hormone therapy). For men with advanced prostate cancer (specifically metastatic castration-resistant prostate cancer (mCRPC), medications called PARP inhibitors (specifically called olaparib and rucaparib) are FDA-approved for those patients who have certain genetic mutations in genes that repair damaged DNA, including mutations in BRCA1 and BRCA2. These genetic mutations may sound familiar, as they are famously known for their association with aggressive breast and ovarian cancer. They also are associated with aggressive prostate cancer. For men with MSI-high mutations in their prostate tumor (which is quite rare, with only ~3% of prostate cancers having this mutation), the immunotherapy agent pembrolizumab is approved for these patients, which is typically associated with the mCRPC disease state.
In conclusion, men with high risk-localized prostate cancer should discuss with their cancer doctors the utility of genomic testing. Based on real-world studies, unfortunately, genomic testing of a patient’s blood or their tumors has not had the uptake that would be expected, thus it is important for patients to specifically ask their doctor if genomic testing is appropriate for them. As highlighted above, genomic testing may be important for personalizing treatment, particularly for men with advanced prostate cancer.