Prostate cancer staging is the process by which physicians categorize the risk of cancer having spread beyond the prostate, or equivalently, the probability of being cured with local therapies such as surgery or radiation.
Prostate cancer stage can be assessed by either clinical or pathological staging methods.
Clinical staging usually occurs before the first treatment and tumor presence is determined through imaging and rectal examination, while pathological staging is done after treatment once a biopsy is performed or the prostate is removed by looking at the cell types within the sample.
There are two schemes commonly used to stage prostate cancer in the United States. The most common is promulgated by the American Joint Committee on Cancer (AJCC), and is known as the TNM system, which evaluates the size of the tumor, the extent of involved lymph nodes, and any distant spread and also takes into account cancer grade.
Stage I disease is cancer that is found incidentally in a small part of the sample when prostate tissue was removed for other reasons, such as benign prostatic hypertrophy, and the cells closely resemble normal cells and the gland feels normal to the examining finger.
In Stage II more of the prostate is involved and a lump can be felt within the gland.
In Stage III, the tumor has spread through the prostatic capsule and the lump can be felt on the surface of the gland.
In Stage IV disease, the tumor has invaded nearby structures, or has spread to lymph nodes or other organs.
The Gleason Grading System is based on cellular content and tissue architecture from biopsies, which provides an estimate of the destructive potential and ultimate prognosis of the disease.
Clinical T stage (cT)
cTX: cannot evaluate the primary tumor
cT0: no evidence of tumor
cT1: tumor present, but not detectable clinically or with imaging
cT1a: tumor was incidentally found in 5% or less of prostate tissue resected (for other reasons)
cT1b: tumor was incidentally found in greater than 5% of prostate tissue resected
cT1c: tumor was found in a needle biopsy performed due to an elevated serum PSA
cT2: the tumor can be felt (palpated) on examination, but has not spread outside the prostate
cT2a: the tumor is in half or less than half of one of the prostate gland’s two lobes
cT2b: the tumor is in more than half of one lobe, but not both
cT2c: the tumor is in both lobes but within the prostatic capsule
Tumors which are found to be bilateral on biopsy only but which are not palpable bilaterally should not be staged as T2c.
cT3: the tumor has spread through the prostatic capsule (if it is only part-way through, it is still T2)
cT3a: the tumor has spread through the capsule on one or both sides
cT3b: the tumor has invaded one or both seminal vesicles
cT4: the tumor has invaded other nearby structures
Pathological T stage (pT)
pT2: organ confined
pT2a: Unilateral, one-half of one side or less
pT2b: Unilateral, involving more than one-half of side but not both sides
pT2c: Bilateral disease
pT3: Extraprostatic extension
pT3a: Extraprostatic extension or microscopic invasion of bladder neck
pT3b: Seminal vesicle invasion
pT4:Invasion of rectum, levator muscles, and/or pelvic wall
Evaluation of the regional lymph nodes (‘N’)
NX: cannot evaluate the regional lymph nodes
N0: there has been no spread to the regional lymph nodes
N1: there has been spread to the regional lymph nodes
Evaluation of distant metastasis (‘M’)
MX: cannot evaluate distant metastasis
M0: there is no distant metastasis
M1: there is distant metastasis
M1a: the cancer has spread to lymph nodes beyond the regional ones
M1b: the cancer has spread to bone
M1c: the cancer has spread to other sites, regardless of bone involvement
Evaluation of the histologic grade:
For prostate cancer, cell morphology is graded based on the Gleason grading system.
Describing tumors as well, moderately, and poorly differentiated based on Gleason score of 2–4, 5–6, and 7–10, respectively, persists in SEER and other databases but is generally outdated.
In recent years pathologists rarely assign a tumor a grade less than 3, particularly in biopsy tissue.
Contemporary reporting standard includes the Grade Groups.
For prostate cancer, grade group information and prostate-specific antigen levels are used in conjunction with TNM status to group cases into four overall stages.
Grade Group 1 = Gleason 6 (or less)
Grade Group 2 = Gleason 3+4=7
Grade Group 3 = Gleason 4+3=7
Grade Group 4 = Gleason 8
Grade Group 5 = Gleason 9-10
In the AJCC staging system, the tumor, lymph node, metastasis, gleason grade grouping and Prostate-specific antigen status can be combined into four stages of worsening severity.
While TNM staging is important, systems based just on anatomic features are not well suited for deciding what treatment is best for a patient with prostate cancer, as there is still considerable heterogeneity of prognosis within the stage categories.
It is common to classify patients into high, intermediate and low-risk groups on the basis of these three factors (TNM stage, PSA and Gleason score).
There is no clear division between stage, which is historically a statement of anatomic extent of disease at diagnosis, and prognostic models that may include many features that contribute to clinical outcome.
Patients with low-risk disease are usually treated with active surveillance, prostatectomy, or radiotherapy alone.
Patients with intermediate-risk disease are candidates for prostatectomy or radiotherapy and a short duration of hormonal ablation, a medical castration using a gonadotropin-releasing hormone analog.
Although the role of surgery in these patients remains uncertain, those with high-risk disease are usually treated with radiotherapy and a long duration of hormonal ablation.