Prostate cancer: How to read your blood tests?

What is the prostate?

The prostate is a walnut-sized gland in the male reproductive system. Its size increases with age. It is located under the bladder, in front of the rectum and surrounds the anterior part of the canal that evacuates sperm and urine. The prostate plays a role in the making of semen by producing and storing prostatic fluid (a sub-constituent of semen produced by the seminal vesicles), which mixes with sperm is ejaculated as semen.

How does prostate cancer manifest itself?

The cancer

Prostate cancer refers to the uncontrolled multiplication of prostate cells to form a mass called a malignant tumour. Most often, prostate cancer develops undetected. There are rarely any physical symptoms and it is often discovered during routine examinations, by chance.

Clinical signs

Indeed, the cancerous cells initially develop on the periphery of the gland, so they do not interfere with the passage of urine or sperm. 

Micturition problems (difficulty urinating, burning, frequent need to urinate) or the presence of blood in the urine are symptoms frequently found in patients with prostate cancer. The same is true for disorders related to ejaculation or the presence of blood in the semen. Be careful not to be alarmed to quickly, as there are other, more frequent conditions that give rise to the same clinical symptoms, such as benign prostatic hyperplasia (BPH or prostate gland enlargement) or prostatitis (painful prostate inflammation, caused by infection or not).

Investigating an inflammatory response: Excluding prostatitis

Prostatitis, a differential diagnosis of prostate cancer with BPH, is an inflammation of the prostate often due to infection. Most of the time, the infection is of bacterial origin. Thus, investigating for inflammatory response (inflammation is the body's natural response infection) can help guide the diagnosis.

Standard values:

CRP (C-reactive protein)
< 5mg/L

ESR (Erythrocyte sedimentation rate): the time it takes red blood cells to fall to the bottom of a test tube
Normal rate for females 17-69 years: <20 mm/hr
Normal rate for females >70 years: <35 mm/hr
Normal rate for males 17-69 years: <14 mm/hr
Normal rate for males >70 years: <30 mm/hr

Why this test?

The CRP and ESR are increased during inflammation, presumably caused by infection. It is not uncommon to have to rule out differential diagnoses, especially since prostate cancer is rare before the age of 50: the average age at diagnosis is around 70.

Blood tests for prostate cancer

Discovery

Prostate cancer screening is not systematic either in the UK or elsewhere and is done on a voluntary basis or is proposed by the patient's GP who has noticed potential risk factors. Indeed, there is no standardised procedure for responding to the results of these examinations as they are not 100% reliable. It should be noted that almost half of prostate cancers are not "aggressive": some are slow-growing (over 10-15 years) and have no repercussions on the lives of the men affected. Therefore, treating them is not necessarily beneficial. On the other hand, "aggressive" prostate cancers can often metastasise and are rapidly progressing. 

Generally, the doctor's examination is directed towards the presence of clinical symptoms or the presence of a family medical history. Depending on the situation, the clinical examination is based on a digital rectal examination (DRE) designed to detect a clinical abnormality related to the size, consistency and texture of the prostate gland. Then, a PSA test is conducted to confirm or rule out the diagnosis.

PSA levels in the blood

Standard values:

PSA 
< 3 ng/mL

Why this test? What is PSA?

PSA is the acronym for Prostatic Specific Antigen. It is a protein produced by the prostate and is mainly found in the semen, but a small quantity passes into the bloodstream. Thus, in a healthy individual, PSA is found in small quantities in the blood. It is important to be aware that sexual intercourse or rectal examinations should be avoided in the 48 hours before the PSA test, as they can cause PSA levels to rise and interfere with the test results.

Results of this test:

Abnormally high levels may indicate the presence of prostate cancer. If the rate is higher than the standard value, the diagnostic process requires additional tests. However, an elevated level in the blood can also be explained by age (the older you are, the higher the PSA level is likely to be) or by a benign adenoma or prostatitis. Moreover, a normal PSA level does not mean that cancer cannot be ruled out.

Follow-up

A clear distinction must be made between discovery and follow-up when measuring PSA levels. Indeed, the purpose of follow-up is to monitor the evolution of the cancer: after treatment is initiated, low PSA levels are expected, though an increase in PSA does not necessarily mean there is a recurrence. In short, the PSA level serves as a warning sign in the monitoring of prostate cancer.

Routine blood tests

Complete blood profile: FBC (Full blood count):

Standard values:

WBC (White blood cell count)
Female normal range: 4.0-11.0 x 10⁹/L
Male normal range: 4.0-11.0 x 10⁹/L

RBC (Red blood cell count)
Female normal range: 3.8-4.8 x 10¹²/L
Male normal range: 4.4-5.5 x 10¹²/L

Haemoglobin (Hb)
Female normal range: 120-150 g/L
Male normal range: 130-170 g/L

Haematocrit (Hct)
Female normal range: 0.40-0.50 g/L
Male normal range: 0.36-0.46 g/L

Platelet Count (PLT)
150-400 x 10⁹/L

Why this test?

A full blood count is essential to monitor for several types of conditions, and to assess the patient's general state of health, especially to rule out anaemia (abnormally low red blood cell count). These test results will also be used to determine the precautions to be considered when starting prostate cancer treatment.

Renal panel

Standard values:

Urea
2.5-7.5 mmol/L

Why this test?

A renal panel is used to help monitor and diagnose conditions affecting kidney function, notably kidney failure, which could aggravate the cancer. Levels of urea increase in cases of kidney failure (called uraemia). High levels of urea are not unique to kidney failure and can also occur in the case of high protein diets, dehydration or infection.

Standard values:

Creatinine
Female normal range: 45-84 µmol/L
Male normal range: 59-104 µmol/L

Why this test?

Creatinine levels reflect kidney function. Creatinine is a product of skeletal muscle breakdown. It is mainly eliminated by the kidneys (by glomerular filtration, but also by tubular secretion). Kidney function can be estimated from the renal clearance of creatinine or from its concentration in the blood using formulas for estimating the glomerular filtration rate (GFR).

Electrolytes

Standard values:

Calcium
2.1-2.6 mmol/L

Why monitor calcium levels?

Calcium the main cellular mediator responsible for muscle contraction and is therefore physiologically present in the blood. However, hypercalcaemia (excess levels of calcium in the blood) can occur, particularly in advanced metastatic cancers. Indeed, bone metastasis ("bone mets"), or when cancer cells spread from their original site to a bone, is the cause of increased and irreversible degradation of bone cells. This is why the calcium level is a factor to be closely monitored in cancers. It should be noted that calcium levels are interpreted by taking into account the patient's state of nutrition and hydration.

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