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Last updated August 11, 2019. 9 minute read

Prostate cancer stages and grades—this is what they tell us

Cancer grade refers to how quickly the cancer cells will grow and spread; prostate cancer is graded using the Gleason score. Cancer stage refers to the size of the tumor and whether or not it has spread to other parts of the body; prostate cancer is staged using the TNM system. T= the size of the tumor. N= whether there is any lymph node spread. M=whether there is any metastasis.

Dr Chimene Richa Md Written by Dr. Chimene Richa, MD
Reviewed by Dr. Tzvi Doron, DO

Prostate cancer is the most common non-skin cancer affecting men in the United States. It is estimated that 11% of men will be diagnosed with prostate cancer at some point in their lives. The prostate is about the size of a walnut; it sits at the base of the bladder in front of the rectum. Cancer cells begin slowly growing in the peripheral zone of the prostate gland. If undetected, cancer may grow and spread beyond the prostate gland via three potential routes:

  • Growing into adjacent tissues (invasion)
  • Spreading through the lymph nodes into the lymph system
  • Traveling in the bloodstream to distant tissues, like bone, lung or liver (metastasis)

Once you are diagnosed with prostate cancer, your healthcare provider will need to determine the grade and staging of your cancer to determine the best course of treatment.

You can learn more about the prostate gland and its anatomy by clicking here.

What’s the difference between cancer grading and staging?

If your healthcare provider suspects prostate cancer, he or she will refer you for a prostate biopsy. During this procedure, a small sample of prostate cells from the tumor is removed and evaluated under the microscope. This microscopic examination is what gives a cancer its grade. Cancer (or tumor) grade refers to how quickly it may grow or spread (Dana-Farber, 2019). For the most part, the lower the grade, the slower the growth of the tumor.

In addition to finding out the grade of your prostate cancer, it is important to determine its stage. Cancer stage refers to the size of the tumor (Dana-Farber, 2019) and whether or not it has spread to other parts of the body. Stages mean different things for different types of cancer, but usually the higher the number, the more advanced the cancer.

The prostate cancer grading system

Prostate cancer grading is based on the appearance of the tumor cells under the microscope. Low-grade cancer cells look more like healthy cells than do high-grade cells. The two methods used to measure prostate cancer grade are the Gleason score (NCI, 2019) or Grade Group.

While examining the tumor cells, the pathologist looks at the two most common tumor cell patterns referred to as the primary (the most common) and secondary (the second most common) patterns. Each of these patterns is then graded based on how closely they resemble normal prostate tissue.

Grade 1 cells look like normal prostate cells. Grade 5 cells are very abnormal appearing cells. Grades 2-4 are in between; the higher the number, the less the cells look like normal prostate tissue. Almost all prostate cancer has grade 3 cells or higher. Once the pathologist has assigned a grade to the primary and secondary cell patterns, these two numbers are added together to get a total Gleason score. The higher the Gleason score, the more likely the tumor is going to grow or spread to other parts of the body. Since the lowest grade a cancer cell can have is grade 3 (grades 1&2 are rarely used when describing cancerous tissue), the lowest Gleason score for a cancer is grade 6 (total of the primary and secondary scores) and is considered low-grade prostate cancer.

Using the Gleason score, prostate cancers can be divided into three groups:

Gleason Score Prostate Cancer Grade
Gleason score of 6 (or less) low-grade prostate cancer
Gleason score of 7 medium-grade prostate cancer
Gleason score of 8-10 high-grade prostate cancer

In 2014, the International Society of Urological Pathology (ISUP) (Epstein, 2016) came up with a way of using the Gleason score to categorize prostate cancers into “Grade Groups”, ranging from 1 to 5, with 1 being the least likely to grow. For example, if your primary Gleason score is 3 and your secondary score is 4, then you are a Grade Group 2. Alternatively, if the primary pattern is a Gleason score 4 (higher grade cancer cell) and the secondary pattern is a 3, then you are Grade Group 3 (an overall higher cancer grade).

ISUP Prostate Cancer Grade Groups:

Grade group Gleason score Prostate cancer grade
Grade group 1 Gleason score of 6 or less low-grade cancer
Grade group 2 Gleason score 3+4= 7 medium-grade cancer
Grade group 3 Gleason score 4+3= 7 medium-grade cancer with more abnormal cells
Grade group 4 Gleason score of 8 advanced-grade cancer
Grade group 15 Gleason scores 9-10 advanced-grade cancer

Prostate cancer staging

In addition to using prostate cancer grade, your healthcare provider will need the cancer stage to determine the best treatment for you. Remember, the cancer stage refers to the size of the tumor and whether or not the cancer has spread. More information than just the prostate biopsy is often necessary for staging; your healthcare provider may order imaging tests such as ultrasound, CT, MRI, etc. The most common staging system for prostate cancer is the one used by the American Joint Committee of Cancer (AJCC), also known as the TNM system. There are five data points used to come up with the overall stage:

  • The size of the tumor (T category)
  • If the cancer has spread to lymph nodes (N category)
  • If the cancer has spread or metastasized to other parts of the body (M category)
  • The PSA level at the time of diagnosis
  • The Gleason score or Grade Group

The TNM categories are further subdivided into smaller subgroups, indicated by numbers (1,2,3, or 4) after the T, N, or M, which gives more details about the characteristics of the cancer. The higher the number, the more advanced the cancer.

T= the size of the tumor

  • T1 – The healthcare provider did not feel a tumor during a digital rectal exam (DRE) or see it on ultrasound, but cancer cells were found in prostate tissue from a biopsy or surgical procedure
  • T2 – The healthcare provider could feel the tumor on DRE or see it on imaging, but it is only in the prostate
  • T3 – The tumor has expanded outside the prostate and may have grown into the seminal vesicles
  • T4 – The tumor has expanded into other nearby tissues, such as the rectum, bladder, or wall of the pelvis.

N= whether there is any lymph node spread

  • NX – The lymph nodes have not been checked for cancer.
  • N0 – There is no cancer in nearby lymph nodes.
  • N1 – Cancer has spread to nearby lymph nodes.

M=whether there is any metastasis

  • M0 – Cancer has not spread past nearby lymph nodes.
  • M1 – Cancer has spread past nearby lymph nodes to distant sites.
    • M1a – Cancer has spread to distant lymph nodes (outside of the pelvis).
    • M1b – Cancer has spread to bones.
    • M1c – Cancer has spread to distant organs, including lung, liver, or brain.

Prostate cancer staging: stage grouping

One of the most important things to consider when determining treatment is your prostate cancer stage. Once, your healthcare provider has determined the TNM stage, he or she will then combine that information with the PSA level and Gleason Grade Group to get your stage group. AJCC Stage Groups (ACS, 2019) are numbered I-IV (1-4), with higher numbers meaning more advanced disease. They can also be subdivided into smaller groups, indicated by letters (A, B, or C), with C being the more advanced disease.

AJCC stage Stage grouping
Stage I – T1 or T2, N0, M0
– Cancer growing in the prostate but hasn’t spread
– Gleason Grade group 1 (Gleason score 6 or less)
– PSA less than 10ng/mL
Stage IIA – T1 or T2, N0, M0
– Cancer growing in the prostate but hasn’t spread
– Gleason Grade Group 1 (Gleason score 6 or less)
– PSA less than 20ng/mL
Stage IIB – T1 or T2, N0, M0
– Cancer growing in the prostate but hasn’t spread
– Gleason Grade Group 2 (Gleason score 3+4=7)
– PSA less than 20ng/mL
Stage IIC – T1 or T2, N0, M0
– Cancer growing in the prostate but hasn’t spread
– Gleason Grade Group 3 (Gleason score 4+3=7) or Group 4 (Gleason score of 8)
– PSA less than 20ng/m
Stage IIIA – T1 or T2, N0, M0
– Cancer growing in prostate, but hasn’t spread
– Gleason Grade Group 1-4(Gleason score 8 or less)
– PSA at least 20ng/mL
Stage IIIB – T3 or T4, N0, M0
– Cancer has spread from the prostate to the seminal vesicles or other nearby structures like rectum, bladder, or pelvic wall
– Cancer has not spread to lymph nodes or other parts of the body
– Gleason Grade Group 1-4(Gleason score 8 or less)
– PSA can be any value
Stage IIIC – Any T, N0, M0
– Cancer may or may not have spread from the prostate to the seminal vesicles or other nearby structures like rectum, bladder, or pelvic wall
– Cancer has not spread to lymph nodes or other parts of the body
– Gleason Grade Group 5 (Gleason score 9 or 10)
– PSA can be any value
Stage IVA – Any T, N1, M0
– Cancer may or may not have spread from the prostate to the seminal vesicles or other nearby structures like rectum, bladder, or pelvic wall
– Cancer has spread to nearby lymph nodes
– Cancer has not spread to distant lymph nodes or other parts of the body
– Any Gleason Grade Group
– PSA can be any value
Stage IVB – Any T, and N, M1
– Cancer may or may not have spread from the prostate to seminal vesicles or other nearby structures like rectum, bladder, or pelvic wall
– Cancer may or may not have spread to nearby lymph nodes
– Cancer has spread to distant lymph nodes and/or other parts of the body, such as bone, lung, liver, or brain
– Any Gleason Grade Group
– PSA can be any value

What do staging and grading mean for me?

You may be wondering why do you need all of this information or if this “alphabet soup” is really necessary. Deciding on treatment necessarily involves a discussion with you and your healthcare provider, but it also includes the input of multiple specialists. Depending on your stage, a medical oncologist (cancer specialist), a radiation oncologist (also a cancer specialist), and a urologist (urinary and male reproductive system specialist) may be involved in the decision making process. The staging and grading systems help you and all of your healthcare providers choose which treatment path is best for your particular situation. However, staging is not the only information your healthcare providers need. Your symptoms, age, life expectancy, and personal preferences should be taken into consideration when deciding on treatment.

Healthcare providers use a general guideline (ACS, 2019) for initial treatment based on stage groups. It is a place for them to start the discussion with you about appropriate options. 

Stage group Treatment options
Stage I – Watchful waiting (tracking symptoms)
– Active surveillance (monitoring PSA levels)
– Radiation therapy (external beam or brachytherapy)
– Radical prostatectomy (removal of the prostate)
Stage II – Active surveillance
– Radiation therapy (external beam and/or brachytherapy)
– Radical prostatectomy
– Hormone therapy
Stage III – Radiation therapy +/- hormone therapy
– Radical prostatectomy
Stage IV – Hormone therapy +/- chemotherapy
– Radiation therapy and hormone therapy
– Radical prostatectomy
– Transurethral resection of the prostate (TURP)
– Treatments aimed at the site of metastasis, such as bone
– Active surveillance
– Treatments to improve symptoms, like pain or urinary difficulties (palliative care)

How do prostate cancer stages and grades affect survival rates?

Overall, the prostate cancer survival rate is 98%, and most men with this disease will die of other conditions rather than the prostate cancer itself. However, if you look at survival rates by stage, it has been shown that the more advanced forms of prostate cancer have a lower survival rate. The National Cancer Institute’s (NCI) Surveillance, Epidemiology, and End Results Program (SEER), which is the database that compiles the incidence and survival rates, sorts prostate cancer into localized, regional, and distant rather than using the TNM system (NCI, n,d.).

  • Localized- cancer has not spread outside of the prostate (Stage I, II, and some stage III cancers)
  • Regional- cancer has spread outside of the prostate to adjacent structures and lymph nodes (Stage IIIB and IVA cancers) 
  • Distant- cancer has spread to remote parts of the body, such as bones, liver, or lungs (Stage IVB cancers)

Here are the 5-year relative survival rates for men with prostate cancer based on the SEER database information.

SEER stage 5-year survival rate
Localized 100%
Regional 100%
Distant 30.5%
Unknown stage 81.6%
All SEER stages combined 98%

You can learn more about prostate cancer survival rate by clicking here.

In conclusion

Being diagnosed with cancer can be difficult for both you and your loved ones. There is a great deal of information available about staging, survival rates, treatments, etc. Talking to your healthcare providers about your cancer can help you translate the “alphabet soup” into an actionable plan. It is important to remember that cancer affects each person differently; doctors have guidelines to follow, but no single treatment plan works best for everyone. Work as a team with your healthcare provider to come up with the best strategy for you to conquer prostate cancer.

Vitals

  • Cancer grade refers to how quickly the cancer cells will grow and spread; prostate cancer is graded using the Gleason score.
  • Cancer stage refers to the size of the tumor and whether or not it has spread to other parts of the body; prostate cancer is staged using the TNM system.
  • Treatment of prostate cancer is based on a combination of age, life expectancy, and personal preferences, in addition to cancer grade and stage.
  • In general, the higher the grade or stage, the more likely it is that the cancer will spread.