What Is Nadir?
Nadir means low point. Nadir in PSA (prostate-specific antigen) indicates the lowest PSA level achieved after every treatment like chemotherapy, radiotherapy, and surgery. But it acts as an important prognostic tool in Androgen deprivation therapy (chemotherapy) in prostate cancer.
What Is PSA?
PSA, also called prostate-specific antigen present in the blood, is produced by cancerous and non-cancerous tissue in the prostate gland (a part male reproductive system). It is also found in semen. A small amount circulates in the blood. Higher PSA levels are usually seen in the following:
-
Other common prostate problems like infection and swelling (in elders).
-
Benign prostatic hyperplasia (enlarged prostate gland).
-
Certain medicines.
How Is the PSA Test Done?
A small blood sample is collected from the patient and sent to the lab for detecting PSA levels. Precautions such as avoiding sex and masturbation must be strictly followed for 24 hours before undergoing the test. It is mainly done as a screening test for prostate cancer; cancer screening means looking for cancer signs before symptoms are caused.
Prostate cancer screening is advised mainly because of the following reasons:
-
Cancer grows slowly.
-
Cancer does not spread beyond the prostate gland.
-
It cannot cause any other health problems.
-
A person with prostate cancer can lead a long life before it is diagnosed.
What Are the Drawbacks of PSA Tests?
Challenges in using the PSA test include:
-
PSA tests cannot differentiate between the cancerous and non-cancerous conditions of the prostate. In raised PSA levels, a prostate biopsy is the only way to diagnose the cancer condition, and this biopsy involves the potential risk of prostate.
-
PSA levels help to treat prostate cancer which never affects health. Therefore PSA cannot detect slow-growing cancer from that fast-growing prostate cancer. This is of serious concern in elderly people, where unnecessary intervention could lead to problems such as:
-
Loss of bladder control.
-
Loss of control over bowel movements.
-
Confusing test results: Increased PSA levels do not mean the presence of cancer; a person with low PSA levels can also have cancer.
How Are the PSA Levels Measured?
PSA is measured in nanograms per milliliter of blood (ng/ml). There is no specific set reference range for the PSA test, but many doctors consider 4.0 ng/ml or less than that as normal.
-
4.0 ng/ml: Considered normal.
-
4.0 to 10.0 ng/dl - Increases the chances of prostate cancer.
-
Above 10.0 ng/dl - Indicates the presence of prostate cancer.
PSA Levels at Various Phases of Treatment:
-
After Surgery: After orchiectomy (surgical removal of the prostate), PSA levels drop down to a very low and undetectable level in the blood, but some PSA remains in the blood; hence it is advised to wait for six to eight weeks after surgery to check for PSA levels in the blood. If PSA levels rise after surgery, the doctor will check how fast they rise. A fast increase in PSA levels is a sign of prostate cancer.
PSA Doubling Time: It is the time over which the PSA levels in men double. The prognosis is poor when the PSA level doubles in less than three months.
-
After Radiation Therapy: The fall of PSA levels is much different in radiation therapy when compared to surgery, in surgery sudden fall in PSA levels is noted because of the removal of the prostate gland, whereas in radiation therapy, the cancer cells in the prostate gland shrink in size; hence PSA levels tend to decrease slowly over a period of time. A continuous rise in PSA levels of 2 ng/ml in consecutive tests may indicate further treatment.
PSA Bounce Back: This is seen in both external and internal radiation, where the PSA levels slightly go up for the first two years after the radiation and then drop down eventually.
-
In The Active Surveillance Phase of Prostate Cancer:
PSA levels should be observed very carefully during the patient's observation period. For this, PSA levels before the treatment and immediately after the treatment must be taken into consideration. A quick rise in PSA levels is an alert for emergency treatment. But a rise in PSA levels is not the sole indicator of treatment; this rise in PSA should be matched with prostate biopsy for planning the treatment.
-
In Advanced Prostate Cancer: Advanced prostate cancers are treated either in chemotherapy, radiotherapy, or immunotherapy or in combination. These PSA test levels act as a guide to tell how well the treatment is working.
What Are the Recent Advances in PSA Tests?
Many improvements are made in PSA tests to detect and differentiate between slow, fast-growing, cancerous, and non-cancerous conditions of the prostate gland. Some of the recent advances in PSA tests include the following:
-
Urinary Biomarkers: Prostate cancer antigen three (PCA3) and TMPRSS2-ERG gene are the biomarkers that detect prostate cancer in urine samples.
-
PSA Density: PSA in the blood divided by prostate gland volume; this gives more accuracy in prostate cancer.
-
Free and Total PSA: The total amount of PSA in the blood that is free, which means PSA that is not bound to other proteins, is divided by the total amount of PSA. The lower the free PSA, the more aggressive cancer.
-
PSA Velocity and Doubling Time: PSA velocity is the rate of change in PSA levels over a period of time, and PSA doubling is the time period over which a person's PSA doubles. Both are more useful after surgery and radiation therapy.
-
4K Score: This test takes into consideration different prostate markers like free PSA, total PSA, intact PSA, and human kallikrein2. Along with this age, DRE( direct rectal examination), and biopsy reports assess the risk and aggressiveness of cancer in patients whose screening results are not normal.
Conclusion:
PSA test levels act as monitoring agents after surgery, radiotherapy, and chemotherapy to check prostate cancer recurrence. A rise in PSA levels must be coordinated with other tests, such as biopsy, and imaging tests, for planning the treatment of prostate cancer.
