STAGES
OF PROSTATE CANCER
Prostate
cancer staging is the process by which physicians evaluate the spread of prostate
cancer. This is important because in a good cancer staging system, the stage of
disease helps determine prognosis and assists in selecting therapies. A combination
of physical examination, blood tests, and medical imaging is used to determine
the clinical stage; if tissue is obtained via biopsy or surgery,
examination of the tissue under a microscope can provide pathologic
staging.This distinction is important because the staging used in various nomograms
such as the Partin
Tables are clinical NOT pathological staging.
There
are two schemes commonly used to stage prostate cancer. The most common is the
TNM system, which evaluates the size of the tumor,
the extent of involved lymph nodes, and any metastasis (distant spread). As with
many other cancers, these are often grouped into four stages. Another scheme,
used less commonly, is the Whitmore-Jewett stage.
Whitmore-Jewett staging
TNM staging
Evaluation of the (primary)
tumor ('T')
- TX:
cannot evaluate the primary tumor
- T0:
no evidence of tumor
- T1:
tumor present, but not dectable clinically or with imaging
- T1a:
tumor was incidentally found in less than 5% of prostate tissue resected (for
other reasons)
- T1b:
tumor was incidentally found in greater than 5% of prostate tissue resected
- T1c:
tumor was found in a needle biopsy performed due to an elevated serum PSA
- T2:
the tumor can be felt (palpated) on examination, but has not spread outside the
prostate
- T2a:
the tumor is in half or less than half of one of the prostate gland's two lobes
- T2b:
the tumor is in more than half of one lobe, but not both
- T2c:
the tumor is in both lobes
- T3:
the tumor has spread through the prostatic capsule (if it is only part-way through,
it is still T2)
- T3a:
the tumor has spread through the capsule on one or both sides
- T3b:
the tumor has invaded one or both seminal vesicles
- T4:
the tumor has invaded other nearby structures
It
should be stressed that the designation "T2c" implies a tumor which is palpable
in both lobes of the prostate, that is to say they can be felt on DRE (Digital
Rectal Examination). Tumors which are found to be bilateral on biopsy only but
which are not palpable bilaterally should not be staged as T2c but should be staged
as T1 a,b or c as appropriate. This is known as clinical staging as opposed
to pathological staging which is done after biopsy or surgery. This distinction
is important because the staging used in various nomograms such as the Partin
Tables are clinical NOT pathological staging.
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 bony involvement)
Whitmore-Jewett staging
The
Whitmore-Jewett system is similar to the TNM system, with approximately equivalent
stages. Roman numerals are sometimes used instead of Latin letters for the overall
stages (for example, Stage I for Stage A, Stage II for Stage B, and so on).
- A:
tumor is present, but not detectable clinically; found incidentally
- A1:
tissue resembles normal cells; found in a few chips from one lobe
- A2:
more extensive involvement
- B:
the tumor can be felt on physical examination but has not spread outside the prostatic
capsule
- BIN:
the tumor can be felt, it does not occupy a whole lobe, and is surrounded by normal
tissue
- B1:
the tumor can be felt and it does not occupy a whole lobe
- B2:
the tumor can be felt and it occupies a whole lobe or both lobes
- C:
the tumor has extended through the capsule
- C1:
the tumor has extended through the capsule but does not involve the seminal vesicles
- C2:
the tumor involves the seminal vesicles
- D:
the tumor has spread to other organs
Risk groups
While
TNM staging is important, the TNM stage alone is not sufficient for deciding what
treatment is best for a patient with prostate cancer. Instead, a different category
called "risk groups" is used, which is based on the T-stage of the TNM system
and adds additional information from the Gleason score and prostate specific antigen
(PSA) value. The risk can be described as low risk, intermediate risk,
or high risk. The risk is a useful predictor of having extraprostatic extension,
which is spread of the cancer beyond the prostate gland itself. Bear in mind,
as stated above it is the clinical NOT pathological staging that
is usually used in such predictive models and also that the models themselves
do not neccessarily apply in individual cases.
Although
slightly different criteria are used for assigning risk, one such system defines
low risk as a PSA less than 10, a Gleason score of 6 or lower, and a T-stage
of T2a or lower; high risk is a PSA more than 20, a Gleason score of 8
or higher, or T2c; intermediate risk is a PSA of 10 to 20, T2b, or a Gleason
of 7.
The
Partin Tables indicate
the estimated probabilities of spread beyond the gland when the three factors
referred to above are used.
Advanced Disease
The
following is a commentary and a set of definitions which Mike Scott posted on
The "New" Prostate Cancer InfoLink
Social Network in reference to a discussion about terminology in advanced
prostate cancer. They may be helpful for some men who are concerned about their
diagnosis or treatment options.
There are very specific and differentiable
categories of "advanced" prostate cancer, and it is important to be careful to
classify them so that people are clear about the differences. What PATIENTS may
want to call these (as opposed to what clinicians may want to call them) is important,
but let me see if we can get the basics down first:
"Advanced prostate
cancer" is any form of prostate cancer that has probably or actually escaped from
the prostate and the immediate region of the tissues surrounding the prostate,
even if there is no specific evidence of micrometastasis or metastasis, and regardless
of the forms of treatment the patient may have received.
"Lymph-node positive
prostate cancer" (clinical stage N1) is prostate cancer that has progressed into
the regional pelvic lymph nodes. Arguably this is not an advanced form of the
disease, but my belief is that 90 percent of lymph node-positive prostate cancer
is also micrometastatic prostate cancer (see below).
"Hormone-refractory
prostate cancer" is usually defined as prostate cancer that is longer being controlled
by first-line hormonal therapy, as indicated by a rising PSA (regardless of the
patient's clinical stage or evidence of metastasis).
"Androgen-independent"
or "Castration-resistant prostate cancer" is usually defined as prostate cancer
that is no longer responding to any "standard" form of hormonal therapy such as
LHRH agonists or antagonists, antiandrogens, estrogens, or even Ketaconzole (regardless
of the patient's clinical stage or evidence of metastasis). Note that with the
coming of Abiraterone, we may have to redefine this expectation since Abiraterone
is in fact a form of hormonal therapy.
"Micrometastatic prostate cancer"
(clinical stage NxMo) is cancer in which it is clear from the patient's history
and clinical signs (e.g., a rising PSA after first-line surgery and second-line
radiation) that the cancer has metastasized, even though there is no actual evidence
of metastatic disease.
"Metastatic prostate cancer" (clinical stage NxM1)
is cancer in which there is clear evidence of metastasis to the bones or other
tissues on the basis of some form of imaging scan (bone scan, CT scan, MRI).
"Taxane-resistant
prostate cancer" is cancer that has stopped responding to docetaxel-based chemotherapy
(or chemotherapy based on some other form of taxane).
