The importance of the prostate cancer stages and grades lies in the fact that it helps the doctor to finalize the options of the treatment plan for each case and to gauge how successful, your treatment will be. It also helps to surmise the prognosis and the survival rate of the case.
Defining the stage of the prostate cancer
The stage of prostate cancer tells us about the size of the cancer growth and whether it has spread outside the prostate gland.
Assessment of the stage involves a number of tests and other measurements to determine the malignant tumor’s location and extent, whether it has spread, how aggressive it is, and how much discomfort it causes to the patient.
The staging of prostate cancer is important to determine the patient’s chances of survival. Some cancers are highly treatable and treatment can be successful even in the late stage. Some cancers are defiant to treatment and offer tough resistance even in the early stages. Prostate cancer, however, is often very treatable.
The first thing that your doctor does after your prostate cancer is diagnosed, is to determine the stage of your cancer. Once he determines your stage, he can then plan and recommend the best possible course of treatment for you.
Defining the grade of the prostate cancer
While the stage tells you the condition of your cancer at the macro-level (about its size and spread), the grade looks at the cancer cells under the microscope and defines them and their action at the micro-level. Grading tells you how fast your cancer is growing.
Conventionally, prostate cancer is graded according to the Gleason Score. This is a system named after a pathologist, Dr. Donald Gleason, who developed it in the 1960s.
Dr. Gleason categorized the cancerous cells into 5 distinct patterns as they change from normal cells to tumor cells.
These five distinct patterns are then graded on a scale from 1 to 5. Normal prostate tissue cells are classified as grade 1.
Staging prostate cancer
There are two ways to stage prostate cancer:
- Clinical staging. Clinical staging is based on the clinical findings of Digital rectal examination (DRE), results of the prostate-specific antigen (PSA) test, and the Gleason score. These findings will tell the doctor whether further studies are required such as x-rays, CT scans, MRI, and bone scans. These studies will help the doctor to clinically stage cancer.
- Pathological staging. During surgery, the surgeon excises the entire prostate gland and the neighboring lymph nodes and sends them to the laboratory for histopathology. The finding of histopathology provides further information about the stage of prostate cancer.
TNM Staging System
The American Joint Committee on Cancer (AJCC) developed the TNM system to stage cancer. This system uses the results of diagnostic tests and scans to answer certain relevant questions. TNM stands for Tumor, Node, Metastasis.
- Tumor (T): How large is the primary tumor (extent) and where is it located?
- Node (N): Has the tumor spread to the nearby lymph nodes? If so, where and how much?
- Metastasis (M): Has cancer spread to other parts of the body such as bones and the liver? If so, where and how much?
The doctor uses the information about the stage of your cancer along with the result of your PSA blood test and the Gleason score (grade determined by the appearance of your cells under a microscope) to plan the treatment. This is done on a case-to-case basis.
The answers are studied in combination to determine the stage of cancer. There are five set stages starting from stage 0, stage 1 to 4. Stages play an important part in helping the doctor plan the right treatment for you.
Gleason score for grading prostate cancer
The Gleason scoring system is the most common system to grade prostate cancer. The cancer cells look different from normal cells. The more different they are in their appearance, the more aggressive the cancer is.
Cancer cells that look similar to healthy cells receive a low score. Cancer cells that look a lot different are more aggressive and receive a higher score.
Looking under the microscope, the pathologist assigns the numbers 1 to 5 to grade the most common (primary) and second most common (secondary) type of cells he sees in the tissue sample.
In other words, two grades are assigned for each sample. A primary grade is given to describe the cells that comprise the largest part of the tumor and a secondary grade is given to describe the cells of the second largest area.
- Grade 1: The tissue appears very similar to the normal prostate cells.
- Grades 2-4: Cells with a lower score appear very much like normal cells and represent a less aggressive cancer. Those with a higher score look vastly different from the normal cells and tell you that they will most likely grow faster.
- Grade 5: Most cells graded 5 look very different from normal cellular appearance. These cells are considered “high-grade” and have mutated to such an extent that they do not resemble normal cells at all.
With this grading system, the numbers allotted to the two most common cellular patterns are added. together to arrive at a Gleason Score
For example, in a histopathological sample taken from the biopsy, the most common type of cell is graded 3 and the second most common type is graded 4, the Gleason Score will be 3 +4 =7.
Similarly, where the most common cell type is 4 and the second most common type is 3, the Gleason Score would still be 7. But, the grade 4+3 cancer would develop much differently than 3+4 and would require more treatment.
To get your Gleason Score, the doctors add your primary and secondary numbers. The Score tells you the type of prostate cancer, whether silent or aggressive. A low Gleason score of 6 indicates low-grade cancer, a score of 7 indicates moderate-grade cancer, and a Score of 8, 9, 10 indicates a high-grade cancer
Let’s translate the scores:
Gleason Score 6: The cells as seen under the microscope look similar to the normal healthy prostate cells, are well-differentiated and the cancer is slow-growing and less likely to spread.
Gleason Score 7 (3+4): Again, most cells look similar to the normal prostate cells and the cancer is likely to grow very slowly.
Gleason Score 7 (4+3): The cells look less like the normal prostate cells. The cancer is likely to grow at a moderate rate
Gleason Score 8-10: The cells look very abnormal, the tumor is poorly differentiated, very aggressive, and likely to spread quickly.
Once the doctor arrives at the stage and the grade of the prostate cancer, he then can plan the best possible treatment options for you.
Cancer stage grouping
Doctors assign the stage to the cancer by taking into consideration the T, N, and M classifications and the PSA level.
- Cancer in this early stage is usually slow-growing.
- It cannot be felt on DRE.
- PSA levels are low.
- The cancer cells resemble healthy cells.
- The tumor is confined to the prostate.
- PSA levels may be moderately high or low.
- The prostate cancer is small but can grow and spread.
- The tumor cannot be felt on DRE.
- PSA levels are medium
- The cancer cells are well differentiated.
- The tumor is large but confined to the prostate, as long as the cancer cells are still well differentiated.
- The tumor is confined to the prostate
- It may be large enough to be felt during DRE.
- The PSA level is medium.
- The cancer cells are moderately differentiated.
- The tumor is confined to the prostate.
- It may be felt during DRE.
- The PSA level is medium.
- The cancer cells may be moderately or poorly differentiated.
- PSA levels are high
- The tumor is growing
- The cancer is of high grade, which is likely to grow and spread.
- The cancer has spread outside the prostate into neighboring tissues and possibly to the seminal vesicles.
- The PSA level is high.
- The tumor has spread beyond the prostate gland and may have invaded the bladder or rectum.
- The cancer cells across the tumor are poorly differentiated and look very different from healthy cells.
- The cancer has spread beyond the prostate.
- The cancer has spread to the regional lymph nodes.
- The cancer has spread to the distant lymph nodes and other parts of the body including the bones.
What Are Prostate Cancer Survival Rates by Stage?
According to the American Cancer Society:
- The 5-year survival rate for most men with localized prostate cancer is 100%.
- The relative 10-year survival rate is 98%
- The 15-year relative survival rate is 91%
- For men diagnosed with metastatic prostate cancer that has spread beyond the prostate to other parts of the body, the 5-year survival rate is 30%.
Relative survival rate means the percentage of men who live the denoted number of years after being initially diagnosed.
However, please note that since these figures are of cancers diagnosed up to 15 years ago, you may live more than the years mentioned because of advances in prostate cancer treatment technology.