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.
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).
T1 – It 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.
N0 – No spread of tumor to nearby lymph nodes
M0 – No spread of tumor to distant body parts
Gleason’s Scoring and Grading for Prostate Cancer
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).
|Gleason Grade Group||Gleason Score||Gleason Pattern|
|4||8||4+4, 5+3, 3+5|
|5||9 or 10||4+5, 5+4, 5+5|
What are the 4 Stages of Prostate Cancer?
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.
|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|
Survival according to Stage of Prostate Cancer
It is calculated based on whether the disease is Localised, Regional or Dstant.
- Cancer is limited to the prostate.
- 5 year survival nearly 100%.
- Cancer has spread to nearby structures or lymph nodes
- 5 year survival nearly 100%.
- Cancer has spread to distant body parts.
- 5 year survival 31%.
Prostate Cancer Staging Investigations
Digital Rectal Exam (DRE)
- It is a type of physical examination performed to find any abnormality (bumps or hard areas) in the prostate or nearby structures.
- In this test, a doctor inserts a lubricated, gloved finger into the rectum via the anus to physically examine the prostate and nearby internal structures.
- In case of an abnormality, detailed investigations are required to establish the diagnosis of prostate cancer.
- But it is not very sensitive, and further testing may be required even if it is normal if there is a suspicion of the disease.
PSA (Prostate Specific Antigen) Assay
- Prostate-specific antigen or PSA is the biomarker for prostate cancer. PSA may be falsely elevated in conditions other than prostate cancer. Most commonly seen are urinary tract infection, bladder catheterization, needle biopsy of prostate and transurethral resection of the prostate.
- Normal PSAs levels also vary with the age of a person. It is less than 2.5 in 40 to 49 years, less than 3.5 in 50 to 59 years, less than 4.5 in 60 to 69 years and less than 6.5 in 70 to 79 years of age.
- But we can never be 100% sure just based on PSA. It guides us for further investigations and confirms the disease by DRE, biopsy, and imaging.
- So to understand it better we come to the free to total PSA ratio. PSA levels of 4 to 10 are overlapping for benign hypertrophy of prostate and prostate cancer, so free to total PSA ratio will help us to differentiate these two conditions. If the ratio is less than 10%, it goes in the favor of cancer. If the ratio is less than 10%, it goes in the favor of cancer.
- Along with other factors (age, race, and family history), it may help to indicate whether further investigations are required. It can help in determining the overall stage of disease and in determining the appropriate treatment option. It can also be used to assess the efficacy of treatment and disease progression/recurrence.
Transrectal ultrasound (TRUS)
- TRUS of the prostate, first described by Wantanabe and colleagues (1968)
- Should be performed in both the transverse and the sagital planes.
- 39% of all cancers are isoechoic and up to 1% of tumors may be hyperechoic. A hypoechoic lesion is malignant in 17% to 57% of cases ( Frauscher et al, 2002a ),
- This helps the doctor to examine the prostate along with the nearby structures for any abnormality.
- This test can measure the size of the prostate or the presence of any abnormalities and can guide a biopsy needle to take biopsy samples from the affected areas.
Prostate Biopsy (TRUS Guided)
Indications of TRUS-guided prostate biopsy-
- Diagnosis of suspected symptomatic prostate cancer (i.e., bone metastasis, cord compression).
- Screening for prostate cancer in asymptomatic patient > age 50 with > a 10-year life expectancy (if strong family history or if African American, consider screening at age 45).
- Prostate nodule or significant prostate asymmetry regardless of PSA level.
- PSA > 4.0 ng/dL regardless of age. In men < age 60-65 years, consider biopsy if PSA > 2.5 ng/dL. If PSA > 0.6 ng/dL at age 40.
- Increased PSA velocity (>0.75-1.0 ng/dL/yr)
- Prior to intervention in symptomatic benign prostatic hyperplasia (e.g., surgical therapy or initiation of 5α-reductase inhibitors)
- Prior to cystoprostatectomy or orthotopic urinary diversion
- To diagnose failed radiation therapy before use of second-line therapy
- Follow-up biopsy (3-6 mo) after diagnosis of high-grade PIN or ASAP
One or more of the following imaging investigations are required to stage the disease and reassess following treatment-
Computed tomography (CT) scan and Magnetic Resonance Imaging (MRI)
- not routinely recommended
- low sensitivity
- may be appropriately reserved for high-risk patients (those with locally advanced disease by DRE, a PSA greater than 20 ng/mL, or men with poorly differentiated cancer on needle biopsy).
- Intravenous urography is rarely obtained to stage prostate cancer
- chest radiograph is a low-yield examination
PSMA (Prostate Specific Membrane Antigen) Positron emission tomography (PET) scan
- This is useful for staging of prostate cancer.
- Better sensitivity and specificity compared to FDG-PET, in cases of prostate cancer.
- In this test, a radioactive material is injected into the vein of the patient, which gets accumulated in the areas of bones affected by the disease, which are then detected with the help of radioactivity detectors. In this way, it may help to detect the spread of cancer to bones.
- Most sensitive modality for the detection of skeletal metastases (Schaffer and Pendergrass, 1976 ; Gerber and Chodak, 1991 ; Terris et al, 1991).
- Skeletal radiography is obtained only to confirm a positive bone scan in men at low risk for bone metastases.
- Bone metastases at diagnosis are rare in men without bone pain the routine use of bone scans in this population may not be useful.
- Bone scans are not routinely obtained for patients with PSA levels less than 10 ng/mL and no bone pain.