Prostate Cancer TNM Staging Explained

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Prostate cancer staging helps to determine the disease prognosis and to select an appropriate treatment strategy.

TNM is the most commonly used staging system for prostate cancer. It uses mainly 5 parameters: “T” stands for “Tumor”; “N” for “Lymph Nodes”; and “M” for “Metastasis”. the PSA level; and the Grade group (based on the Gleason score).

Numbers and/or letters after T (0, 1a, 1b, 1c, 2a, 2b, 2c, 3a, and 3b), N (0 and 1), and M (0 and 1) provide more details about each of these parameters.

PSA level is indicated in nanograms per milliliter (ng/mL). Grading (1 to 5) is assessed based on Gleason score (as described below).

Gleason scoring system involves scoring of prostate cancer based on the extent of abnormality observed in the collected biopsy samples (usually the Gleason score ranges from 3 to 5 for a single biopsy sample).

Since prostate cancer is a multifocal disease, the score for different biopsy samples collected from the same patient may differ. Thus, score of specimen with most predominant Gleason score is added to the highest Gleason score observed, to give overall Gleason score (that may range from 6 to 10). Further, Gleason grade groups (1 to 5) are derived according to the following table:

Gleason Grade Group Gleason Score Gleason Pattern
1</=6</=3+3
273+4
374+3
48 4+4, 5+3, 3+5
59 or 10 4+5, 5+4, 5+5

Once T, N, M, PSA, and grade group are determined through different diagnostic techniques, this information is combined to assign an overall stage (from 0 to IV) to the disease.

T1 – Tumor that is not palpable or visible on imaging. it is an incidental finding on prostate excision or biopsy done for some other reason.

T2a – Tumor involving less than half of one lobe of the prostate

T2b – Tumor involving more than half of one lobe of the prostate

T2c – Tumor involving both lobes of the prostate

Prostate Cancer TNM staging

T3a – Extracapsular extension of tumor without any adjacent organ involvement

T3b – Extracapsular extension to involve seminal vesicle

T4 – Tumor invading adjacent structures like bladder, rectum, perineal body, or pelvic wall. 

Prostate Cancer - T staging (T3, T4)

N0 – No spread of tumor to nearby lymph nodes 

N1 – Tumor has spread to regional lymph nodes

M0 – No spread of tumor to distant body parts

M1 –  Spread to a distant body parts such as bones, lungs, liver, brain, etc.

Prostate Cancer N and M Staging

Prostate Cancer Staging:

Stage TNM Score, PSA (ng/mL), Grade Group (GG)
I T1a-2 N0 M0 PSA<10 GG=1
IIA T1a-2a N0 M0 PSA>/=10,<20 GG=1
T2b-2c N0 M0 PSA<20 GG=1
IIB T1-2 N0 M0 PSA<20 GG=2
IIC T1-2 N0 M0 PSA<20 GG=3-4
IIIA T1-2 N0 M0 PSA>/=20 GG=1-4
IIIB T3-4 N0 M0 Any PSA GG=1-4
IIIC Any T N0 M0 Any PSA GG=5
IVA Any T N1 M0 Any PSA Any GG
IVB Any T Any N M1 Any PSA Any GG

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In the following video, CancerBro explains the anatomy of prostate gland that will help to understand the STAGING better.

Video Transcript:

We will start with the normal prostate anatomy. It lies in the pelvic region below the urinary bladder and urethra passes through it, causing an obstruction on enlargement.

Below the prostate lies the perineal body which acts as the urethral sphincter and controls the passage of urine.

Above lies, the urinary bladder and rectovesical pouch and rectum and anal canal lie behind the prostate.

Now let’s look the at the Prostate Cancer TNM Staging:

Video Transcript:

Now we come to the T staging of the prostate cancer. T1 is clinically inapparent disease with no abnormality on palpation or imaging.

It maybe an incidental finding on excision of prostate done for some other reason or it maybe diagnosed after biopsy of prostate done for elevated PSA.

T2 disease is localized to the prostate. It may be diagnosed with palpation or imaging. It is called as T2a when it occupies less than half of one lobe of the prostate.

T2b if it occupies more than 50% of one lobe of the prostate.

Remember that all cases of the T2 disease are confined to the prostate.

Extracapsular extension of the tumor without any external organ infiltration is called as T3a.

And an extracapsular extension to involve seminal vesicles is called as T3b.

T4 disease is infiltration of the adjacent organs. In this figure, the tumor infiltrates the perineal body.

Here it extends posteriorly to involve the rectum.

And here it extends superiorly to infiltrate the urinary bladder.

It may also extend laterally to involve the pelvic wall.

This was T staging, now we come to the N-staging or nodal staging. Absence or regional lymph nodes involvement is called as N0, whereas involvement of regional lymph nodes is called as N1.

M1 or metastatic disease includes involvement of non-regional lymph nodes or spread to the distant organs.

With this, we come to the end of Prostate cancer TNM staging.

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