What are the stages of prostate cancer?
The term to stage a cancer means to describe the evident extent of the cancer in the body at the time that the cancer is first diagnosed. Clinical staging of prostate cancer is based on the pathology results, physical examination, PSA, and if appropriate, radiologic studies. The stage of a cancer helps doctors understand the extent of the cancer and plan cancer treatment. Results of the treatment of similar Gleason score prostate cancer found at the same or similar stage can help the doctor and patient to make important decisions about choices of treatment to recommend or to accept.
Cancer staging is first described using what is called a TNM system. The "T" refers to a description of the size or extent of the primary, or original, tumor. "N" describes the presence or absence of, and extent of spread of the cancer to lymph nodes that may be nearby or further from the original tumor. "M" describes the presence or absence of metastases -- usually distant areas elsewhere in the body other than regional (nearby) lymph nodes to which the cancer has spread. Cancers with specific TNM characteristics are then grouped into stages, and the stages are then assigned Roman numerals with the numerals used in increasing order as the extent of the cancer being staged increases or the cancer prognosis worsens. Prognosis is finally reflected by considering the patient's PSA score at presentation as well as their Gleason score in assigning a final stage designation.
The American Joint Commission on Cancer (AJCC) system for prostate cancer staging is as follows:
T designations refer to the characteristics of the prostate cancer primary tumor.
T1 prostate cancers cannot be seen on imaging tests or felt on examination. They may be found incidentally when surgery is done on the prostate for a problem presumed to be benign, or on needle biopsy for an elevated PSA.
- T1a means that the cancer cells comprise less than 5% of the tissue removed.
- T1b means that cancer cells comprise more than 5% of the tissue removed.
- T1c means that the tissue containing cancer was obtained by needle biopsy for an elevated PSA.
T2 prostate cancers are those that can felt (palpated) on physical examination of the prostate gland (on digital rectal exam) or that can be visualized with imaging studies such as ultrasound, X-ray, or related studies. The prostate gland is comprised of two halves or lobes. The extent of involvement of those lobes is described here.
- T2a means the cancer involves one half of one lobe of the prostate or less.
- T2b means the cancer involves more than half of one lobe but does not involve the other lobe of the prostate.
- T2c means that the cancer has grown into or involves both lobes of the prostate.
T3 prostate cancers have grown to the extent that the tumor extends outside of the prostate gland. Adjacent tissues, including the capsule around the prostate gland, the seminal vesicles, as well as the bladder neck, may be involved in T3 tumors.
- T3a means that the cancer has extended beyond the capsule (the outer edge) of the prostate gland but not into the seminal vesicles.
- T3b means that the cancer has invaded into the seminal vesicles.
T4 prostate cancers have spread outside of the prostate gland and have invaded adjacent tissues or organs. This may be determined by examination, biopsy, or imaging studies. T4 prostate cancer may involve the pelvic floor muscles, the urethral sphincter, the bladder itself, the rectum, or the levator muscles or the pelvic wall. T4 tumors have become fixed to or invaded adjacent structures other than the seminal vesicles.
The NCCN guidelines prostate cancer version 2.2017 indicate the following:
CT scan is used for the initial staging in select patients including
- T3 or T4 disease, and
- T1 or T2 disease and nomogram probability of lymph node involvement > 10% may be candidates for pelvic CT. A nomogram is a predictive tool that takes a set of information (data) and makes a prediction about outcomes.
Standard MRI techniques can be considered for the initial evaluation of high-risk patients including
- T3 or T4 disease, and
- T1 or T2 disease and nomogram indicating probability of lymph node involvement > 10% may be candidates for pelvic MRI.
Bone scan is recommended in the initial evaluation of patients at high risk for skeletal metastases including
- T1 disease with PSA > 20, T2 disease and PSA > 10, Gleason score > 8 or T3/T4 disease; and
- any stage disease with symptoms of bone metastases (for example, bone pain).
N designations refer to the presence or absence of prostate cancer in nearby lymph nodes, including what are referred to as the hypogastric, obturator, internal and external iliac, and sacral nodes.
- N0 means that there is no prostate cancer evident in the nearby nodes.
- N1 means that there is evidence of prostate cancer in the nearby nodes.
- NX means that the lymph nodes cannot or have not been assessed.
M refers to the presence or absence of prostate cancer cells in distant lymph nodes or other organs. Prostate cancer that has spread through the bloodstream most often first spreads into the bones, then into the lungs and liver.
- M0 means that there is no evidence of spread of prostate cancer into distant tissues or organs.
- M1a means that there is spread of prostate cancer into distant lymph nodes.
- M1b means that there is evidence that prostate cancer has spread into bones.
- M1c means that prostate cancer has spread into other distant organs in addition to or instead of into the bones.
Stratifying prostate cancer by risk
The NCCN guidelines stratify prostate cancer by risk. The risk groups are based on the staging of the prostate cancer, the Gleason score, PSA, and number and extent of biopsy cores positive for cancer. The risk stratification may help decide what treatment option is best for each individual.
Very low risk: stage T1c, Gleason score ≤ 6, Gleason grade group 1, PSA < 10 ng/mL, < 3 prostate biopsy cores positive for cancer, < 50% cancer in any core, PSA density < 0.15 ng/mL/g
Low risk: stage T1-T2a, Gleason score ≤ 6, Gleason grade group 1, PSA < 10 ng/mL
Intermediate risk: stage T2b-T2c, Gleason score 3+4 = 7, Gleason grade group 2 or Gleason score 4+3=7, Gleason grade group 3, or PSA 10-20 ng/mL
High risk: stage T3a or Gleason score 8, Gleason grade group 4, or Gleason 9-10, Gleason grade group 5, PSA > 20 ng/mL
Very high risk: stage T3b-T4, primary Gleason pattern 5, Gleason grade group 5 or > 4 cores with Gleason 8-10, Gleason grade group 4-5