What is Decipher Test for Prostate Cancer?
Decipher test is a transformative genomic test that evaluates the activity of genes in prostate cancer that has a high chance of progressing to advanced prostate cancer. It looks at certain genes to predict how aggressive is the cancer and its chances of metastasis.
A small tissue sample from the prostatectomy tissue is analyzed and the expression levels of RNA biomarkers are determined.
Decipher test is helpful in deciding the course of treatment for men after they undergo surgery for prostate cancer. In one study recommendations to undergo radiation therapy were reduced by 50%, based on Decipher test. Other studies using Decipher test reclassified 60% of men as lower risk category from higher risk. Out of these, 98.5% of patients did not develop metastasis with 5 years of radical prostatectomy.
The classification of the patients in high, low and average risk of developing metastasis is based on the validation in over 2,000 patients in clinical studies. The test accurately predicts the probability of metastasis after surgery. It is an independent assessment of tumor aggressiveness and this information is distinct from that provided by Gleason score or PSA.
What is Prostatectomy?
The prostate gland is an exocrine gland in the male reproductive system that secretes a slightly alkaline fluid that serves as a medium for the semen to flow. Prostate-specific antigen, or PSA, is a protein produced by the cells of prostate gland and released into the blood. The level of PSA in the blood is one of the indicators that help in the diagnosis and management of prostate cancer in men.
Prostate cancer starts with formation of small clumps of cancer cells that are confined to prostate glands. These cancer cells then begin to multiply and spread within the prostate tissue to form a tumor. The tumor may grow and invade surrounding organs like rectum or seminal vesicles. The tumor cells may also travel via the bloodstream or the lymphatic system and invade other parts of the body.
Prostatectomy is the surgical removal of prostate gland and the surrounding organs, and is done for benign or malignant prostate cancer. Simple prostatectomy refers to the surgical procedure in which only part of the prostate is removed. Radical prostatectomy is the removal of entire prostate gland, seminal vesicles and the vas deferens.
Why Decipher Test for Prostate Cancer?
So far the natural history of prostate cancer has been unknown as some of the cancers are indolent whereas others can be aggressive. More patients die with prostate cancer rather than die of prostate cancer. The Decipher Test is the first test which will allow clinicians to do risk stratification for prostate cancer.
Decipher test is now recommended for men who have undergone radical prostatectomy and are faced with post-surgical treatment decisions. The surgeon can evaluate the risk of progression and metastasis and provide the best treatment for prostate cancer.
After undergoing a radical prostatectomy, about 50% of men will show signs of recurrence. Though the pathology may point to high risk, about 90% are not likely to develop metastasis or die of prostate cancer.
The patients who are not likely to develop metastasis may not benefit from the post-surgical treatment and prostate cancer medications. The unnecessary radiation and chemotherapy for prostate cancer may also cause other unwanted side-effects.
Decipher test gives more accurate account of the probability of metastasis that may occur after prostatectomy than information provided by the Gleason score or PSA.
Indications for Decipher Test for Prostate Cancer
A patient is recommended to have a decipher test done if at least one of the following prostate cancer risk factors is present, apart from the advanced prostate cancer symptoms.
- Patients who have had a radical prostatectomy need to be tested further to determine the risk of developing metastasis.
- Positive surgical margins – tumor cells touching the inked edge of the specimen removed surgically.
- Extra-prostatic extension – the extension of tumor beyond the confines of the prostate gland. Also called pT3 disease.
- Invasion of the cancer cells into seminal vesicle.
- Lymph node involvement
- Invasion of neck of urinary bladder
- Perineural or lymphovascular invasion
- High Gleason score of 8 to 10 or tertiary Gleason score of 5.
- Prostate-specific antigen – Pre-surgery PSA more than or equal to 20ng/mL or rise of PSA level after prostatectomy.
Specimen of the Prostate Tumor for Decipher Test
The sample of the tumor removed surgically during prostatectomy has to be collected and stored in the following manner.
Choosing the tissue block:
- The biggest block of tumor tissue that has at least 0.5cm2 of tumor cells.
- A block that shows seminal vesicle invasion or extraprostatic invasion of more than 2 mm.
- The area that shows the highest Gleason grade of tumor.
The tissue block must be formalin-fixed, paraffin embedded, that is, a procedure that involves fixing the tumor tissue block with paraformaldehyde and embedding in paraffin. This is a standard method for preserving and investigating the structure and pathology of clinical tissue material.
Decipher Test Procedure
A sample of tissue taken from the tumor after the surgery is analyzed and subject to Decipher test.
Decipher test measures the expression levels of 22 RNA biomarkers that are involved in multiple biological pathways across the genome associated with aggressive prostate cancer.
Using the measure of expressions of RNA biomarkers, Decipher test helps to calculate the probability of clinical metastasis:
- Within 5 years of radical prostatectomy
- Within 3 years of successive PSA rise
The genomic risk score obtained in the Decipher test is used to predict the probability of the risk of the tumor developing into cancer within 5 years after surgery or 3 years of biochemical recurrence.
Decipher Test Results
Based in the genomic risk score, the patients are classified as being hhigh, average or low risk of probability of developing metastasis.
Patients classified as high risk group may be recommended for radiation therapy. There has been an 80% reduction in metastasis risk in patients who receive adjuvant radiation after being classified as Decipher high-risk.
Patients classified as low risk group may be managed with observation and regular monitoring of PSA levels. Low risk patients have excellent prognosis with salvage radiation therapy and can avoid hormonal therapy.
- Proteomic Sample Preparation from Formalin Fixed and Paraffin Embedded Tissue - (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3857359/)
- Contemporary Role of the Decipher® Test in Prostate Cancer Management: Current Practice and Future Perspectives.Deepansh Dalela, Björn Löppenberg, Akshay Sood, Jesse Sammon, Firas Abdollah Rev Urol. 2016; 18(1): 1–9.
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