Prostate Cancer Staging and Gleason Score Explained

Prostate cancer staging and the Gleason score together decide treatment. The Gleason score, read from biopsy tissue, grades how aggressive the cancer looks on a scale from 6 to 10 and is reported in five Grade Groups. Staging by the TNM system combines rectal examination, biopsy and imaging, ending with a PSMA PET scan or bone scan, to show how far the disease has spread.

Every treatment decision in prostate cancer rests on three numbers and one picture: the PSA (prostate-specific antigen) level, the Gleason score, the stage, and the imaging that defines how far the disease has travelled. The diagnostic pathway of Dr. Amit Goel, Senior Director & Unit Head - Urology, Kidney Transplant, Uro-oncology, Robotic Surgery, Max Hospital, Gurugram, India, is built to produce each of these reliably, from the first blood test in clinic to the PSMA PET scan that precedes treatment. Errors early in the chain, a missed nodule or a poorly sampled biopsy, propagate into every decision downstream. Who is at risk and how the disease presents are covered in the complete guide to prostate cancer symptoms and risk factors.

Who gets a PSA test in Dr. Goel's clinic?

Any man aged 55 or over who walks into Dr. Goel's urology clinic has a PSA test, whatever brought him there, and is told that the test is being done. The reason is that most men with prostate cancer have no symptoms when the disease is found. If the level comes back raised, prostate cancer becomes a working suspicion and further examination and tests follow.

The logic is straightforward. Because early disease is silent, a clinic that tests only symptomatic men will find mostly advanced disease. Routine testing in the at-risk age group is what moves detection to the organ-confined stage, which is now where most cancers are found.

Why a hard nodule on rectal examination means biopsy

A hard prostate nodule found on digital rectal examination proves to be cancer often enough that, in Dr. Goel's practice, it always leads to biopsy.

Dr. Goel examines every male patient who comes to the clinic with a urinary problem. The digital rectal examination is simple: with a gloved, lubricated finger introduced into the rectum, the clinician palpates the prostate. What the finger reaches is the peripheral zone, which is also the zone most susceptible to cancer.

The finding that matters is a hard nodule or hard nodularity. In Dr. Goel's figures, a hard nodule on rectal examination proves to be prostate cancer in roughly 50 to 55 percent of cases. That rate is high enough that his rule is simple: any patient with a palpable nodule on digital rectal examination undergoes biopsy.

The examination therefore works as an independent trigger alongside PSA. A raised PSA or a hard nodule, either one alone, is an indication for tissue diagnosis.

Prostate biopsy: TRUS, MRI fusion and transperineal

A prostate biopsy can be taken through the rectum under ultrasound guidance, with MRI images fused to the ultrasound to target a suspicious area, or through the skin of the perineum. Each route takes small cores of tissue for the pathologist to grade.

Transrectal ultrasound-guided biopsy

Dr. Goel described transrectal ultrasound-guided (TRUS) biopsy as the standard of care for a man with a raised PSA or a hard nodule. Current EAU guidance favours an MRI before biopsy and a transperineal rather than transrectal route. An ultrasound probe is placed in the rectum, the prostate is visualised in real time, and a needle passed through a channel on the probe takes tissue cores from the gland under direct vision.

Dr. Goel's routine is a 12-core biopsy, with cores taken from the base, the mid-gland and the apex. The standard 12-core template samples both sides of the gland at each of these three levels, so that the whole peripheral zone is represented. Where the ultrasound shows a suspicious region, he takes additional targeted cores from it.

One feature of his practice is worth noting. Dr. Goel performs the biopsies himself for all of his patients. His reasoning is accuracy, with the cores targeted precisely wherever a lesion is seen on ultrasound.

MRI-ultrasound fusion biopsy

A newer refinement is the MRI fusion biopsy. A multiparametric MRI of the prostate, a specialised protocol that combines several types of MRI image, is performed first. If it shows a suspicious region, that MRI image is fused with the live ultrasound image during the biopsy, so the needle can be steered precisely into the area the MRI flagged. The approach combines the anatomical detail of MRI with the real-time guidance of ultrasound.

Transperineal biopsy

The third route avoids the rectum altogether. In a transperineal biopsy, the needle passes through the skin of the perineum, the area between the scrotum and the anus, directly into the prostate. Dr. Goel noted that this route needs anaesthesia. It has traditionally been done under general anaesthesia, and it is now also widely performed under local anaesthesia.

What is the Gleason score?

The Gleason score grades how aggressive prostate cancer looks under the microscope by adding together its two most common growth patterns; in biopsy reports it ranges from 6 to 10.

The pathologist's report delivers a number central to treatment planning. The Gleason score describes how aggressive the cancer looks under the microscope, and Dr. Goel was emphatic that it is of paramount importance: treatment is decided substantially on how high the Gleason score is.

How the Gleason score is calculated

Gleason grading describes the architecture of the cancerous glands. At the lower grades the glands are well-defined and orderly. As the grade rises towards 5, the arrangement becomes progressively more poorly differentiated, with less and less resemblance to normal prostatic tissue.

Because a single tumour usually contains more than one pattern, the score combines two. The pathologist identifies the most common pattern (the primary) and the second most common (the secondary) and adds them together. A tumour that is mostly pattern 4 with some pattern 5 scores 4 + 5. One that is mostly pattern 5 with some pattern 4 scores 5 + 4. Both total 9, but the order records which pattern dominates.

The result is a score out of 10. In biopsy reports, the scores encountered range from 6 to 10. Patterns 1 and 2 are, in modern practice, essentially no longer assigned on biopsy, so pattern 3 is the lowest grade of cancer reported and 3 + 3 = 6 is the lowest score.

Gleason Grade Groups 1 to 5

The combined score is reported in five Grade Groups:

• Grade Group 1: a score of 6 or lower.
• Grade Group 2: 3 + 4, a total of 7.
• Grade Group 3: 4 + 3, also a total of 7.
• Grade Group 4: a total of 8 (4 + 4, 3 + 5 or 5 + 3).
• Grade Group 5: a total of 9 or 10 (4 + 5, 5 + 4 or 5 + 5).

The distinction between Grade Groups 2 and 3 shows why the order of the patterns matters. Both total 7, but in Grade Group 2 the less aggressive pattern 3 predominates, while in Grade Group 3 the more aggressive pattern 4 does. Because treatment is decided on the grade, the distinction is recorded rather than collapsed into a single number.

Imaging for prostate cancer: MRI, PSMA PET and bone scan

MRI gives a fairly good indication of whether and where the prostate harbours cancer, and a PSMA PET scan or bone scan shows, once cancer is confirmed, whether it has spread.

Multiparametric MRI

The prostate MRI gives a fairly good indication of whether the gland harbours cancer and where. Dr. Goel was clear, however, that MRI does not replace tissue: a biopsy must be done before any form of treatment begins. MRI's role is to raise or lower suspicion and, through fusion biopsy, to direct the needle.

PSMA PET and bone scan

Once cancer is confirmed, the question becomes whether it has spread beyond the prostate. For final staging, Dr. Goel uses either a PSMA PET scan or a bone scan.

PSMA stands for prostate-specific membrane antigen, and the scan is very specific for prostate cancer. It shows whether there is distant metastasis, and it is performed before treatment is finalised. The same antigen gives its name to lutetium-177 PSMA therapy for advanced disease, discussed in the treatment article.

Prostate cancer staging: the TNM system

Prostate cancer is staged with the TNM system, which describes the primary tumour (T), the regional lymph nodes (N) and distant metastasis (M). Staging integrates the examination, the biopsy and the imaging into a standard description of the disease across these three axes.

T: the primary tumour

• T1: a tumour that cannot be felt on examination.
• T1a: cancer found incidentally in 5% or less of the tissue removed at a transurethral resection of the prostate (TURP) done for benign enlargement.
• T1c: cancer found on a biopsy done because of an elevated PSA.
• T2: a tumour that can be felt on examination and remains within the gland.
• T2a: involves one half of one side of the gland or less.
• T2b: involves more than one half of one side, but not both sides.
• T2c: involves both sides of the gland.
• T3: the tumour has breached the prostatic capsule.
• T4: the tumour has invaded adjacent structures, such as the bladder neck, the external sphincter or the rectum.

T1c is worth singling out, because it is the category created by PSA testing: a cancer with no palpable abnormality, found only because the blood test led to a biopsy. It is the stage at which routine PSA testing in men over 55 aims to catch the disease.

N: regional lymph nodes

• N0: no regional lymph nodes involved.
• N1: involvement of the regional lymph nodes.

M: distant metastasis

• M0: no distant spread.
• M1a: spread to lymph nodes beyond the regional pelvic nodes.
• M1b: spread to bone.
• M1c: spread to other distant organs.

Bone is the most common site of metastasis, which is why M1b disease is the commonest form of metastatic prostate cancer and why bone-directed treatment features so prominently in advanced care.

How staging and the Gleason score combine into a risk group

No single result decides treatment on its own; the stage, PSA and Gleason score are combined into a risk group. A Gleason 3 + 3 cancer confined to one side of the gland in a man with a modest PSA and a clear PSMA PET is a different disease from a Gleason 4 + 5 cancer that has breached the capsule, even though both are called prostate cancer. Dr. Goel combines the stage, the PSA, the Gleason score and the proportion of positive biopsy cores in formal risk tools to classify the disease as low, intermediate or high risk; how that classification drives the choice between surveillance, radiotherapy, surgery and systemic therapy is the subject of the article on prostate cancer treatment options by risk group.