One of the most important steps in your cancer diagnosis process is finding out your prostate “cancer stage.” Knowing your stage of prostate cancer guides your doctor’s decisions about which treatment is appropriate for you. It also provides important information regarding the expected long-term outcomes and survival rates.
Once you are diagnosed with prostate cancer, your doctor may need to perform a test known as a prostate biopsy to see if your cancer has spread and to find out your cancer stage. A prostate biopsy means that small samples of the prostate tissue are removed with a needle and then examined under a microscope. This test will determine your Gleason score and Grade Group. Your PSA level at the time of diagnosis is also important for risk stratification.
Your PSA blood test result and tumor grade on biopsy (the microscopic appearance of the cancer cells from a prostate biopsy) will help your doctor determine the risk of your cancer spreading. Then your doctor will decide if you need additional imaging tests (i.e., CT scan, bone scan, prostate MRI, PSMA PET/CT scan, etc.) to find out if the tumor has spread. For men with very-low and low-risk tumors, the chance of spread is so low that additional tests are not usually needed. However, for men with more aggressive tumors, staging tests are typically recommended.
The most common and well-known staging system of cancers is the American Joint Committee on Cancer (AJCC) TNM system, which was updated most recently for prostate cancer in 2018.
Staging of prostate cancer is based on three categories:
- T category: the size of the primary tumor
- N category: the spread of cancer to the lymph nodes
- M category: whether cancer has spread to other parts of the body
The clinical T stage (noted by the letter “c”) represents how far the tumor in the prostate has grown based on a clinical evaluation. This is mostly based on a physical examination by your doctor (the “digital rectal examination”). However, information from prostate MRI and prostate biopsy may also be helpful.
During stage 1, many tumors cannot be felt or are detected incidentally during other prostate procedures (like a transurethral resection of the prostate). Others may be felt but are contained within the prostate (stage T2). Still others may be felt but may have grown beyond the prostate (stage T3 and T4).
A pathologic T stage (noted by the letter “p”) is assigned for patients that have had their prostate removed. It is based on the microscopic examination by a pathologist (typically more accurate than clinical T stage).
The “N stage” refers to the involvement of lymph nodes in the pelvis. Clinical N stage is typically assigned based on results of a CT scan, MRI, or PSMA PET/CT scan, which may find enlarged lymph nodes suspicious for cancer spread. Pathologic N stage is based on examination of lymph nodes that are removed at the time of prostatectomy.
Finally, the “M stage” refers to metastasis, or spread, to other parts of the body including lymph nodes outside the pelvis, the bones, and other organs. Clinical M stage is based on imaging tests such as bone scan, CT scan, MRI, or PSMA PET/CT scan. Pathologic M stage can be confirmed by biopsy of a metastatic site but this is not often required.
Higher T, N, and M stages are associated with more advanced prostate cancer, and in combination with PSA and Gleason Group, help assign stage grouping from I to IV.
The Stages of Prostate Cancer:
Stage I
- cT1N0M0 (the tumor cannot be felt and is not seen on ultrasound imaging), Grade Group 1 (Gleason score 6 or less), PSA less than 10 ng/mL, OR
- cT2aN0M0 (the tumor is felt or seen in one half or less of one side of the prostate gland), Grade Group 1, PSA less than 10 ng/mL, OR
- pT2N0M0 (the prostate is removed and the tumor is only in the prostate gland), Grade Group 1, PSA less than 10 ng/mL
Stage IIA
- cT1N0M0, Grade Group 1, PSA less than 10-20 ng/mL, OR
- cT2a or pT2N0M0, Grade Group 1, PSA less than 10-20 ng/mL, OR
- cT2b or cT2cN0M0 (the tumor is felt or seen in more than half of one side [cT2b] or both sides [cT2c] of the prostate gland), Grade Group 1, PSA less than 20 ng/mL
Stage IIB
- T1 or T2N0M0, Grade Group 2 (Gleason score 3+4=7), PSA less than 20 ng/mL
Stage IIC
- T1 or T2N0M0, Grade Group 3 or 4 (Gleason score 4+3=7 or Gleason score 8), PSA less than 20 ng/mL
Stage IIIA
- T1 or T2N0M0, Grade Group 1 to 4 (Gleason score 8 or less), PSA at least 20 ng/mL
Stage IIIB
- T3 or T4N0M0 (the cancer has grown outside the prostate gland and may have spread to the seminal vesicles ([T3], or surrounding structures such as the bladder or rectum [T4]), Grade Group 1 to 4, any PSA
Stage IIIC
- Any TN0M0, Grade Group 5 (Gleason score 9 or 10), any PSA
Stage IVA
- Any TN1M0 (the cancer has spread to nearby lymph nodes), any Grade Group, any PSA
Stage IVB
- Any T, any N, M1 (the cancer has spread to other parts of the body such as distant lymph nodes, bones, or other organs [i.e., lungs, liver, etc.]), any Grade Group, any PSA
Based on data from the SEER database (Survivor, Epidemiology, and End Results Program), the 5-year relative survival rate for localized prostate cancer (no disease outside the prostate, stages I-IIIA) and for regional disease (prostate cancer growing into nearby structures or lymph nodes, stages IIIB-IVA) is over 99%. The 5-year survival rate for distant metastasis (stage IVB) is 31%.
Ultimately, the staging of prostate cancer is complex and may be overwhelming to most patients. Each patient should ensure that their doctor explains their stage of prostate cancer and the implications of subsequent treatment.