Prostate Cancer Stages
Staging is a critical phase in determining and defining the pathway for treating a patient diagnosed with prostate cancer.
Staging tells the attending physician the extent to which the disease has progressed and accordingly plan the treatment. It also helps in predicting long-term prognosis.
Broadly, the size of the tumor and its location/spread are the two most important yardsticks universally used for stage determination.
Staging can be done clinically (CLINICAL STAGING) just by physical examination, blood tests or response to radiation therapy (expectant management) and pathologically (PATHOLOGIC STAGING) based on surgery (radical prostatectomy).
Standardized algorithms used for staging and grading:
The Whitmore-Jewett system was used earlier but is very rarely used now. Presently, the American Joint Committee on Cancer (AJCC) TNM system is the commonly used one for staging. The former classifies prostate cancer into stages A through D (D being the most advanced) and has additional sub-stage for more accurate determination. On the other hand, the TNM is based on the size of the primary tumor (T), the degree to which the cancer cells have migrated to adjacent lymph nodes (N), and whether the disease has metastasized (spread) (M) to other organs.
Nowadays, the Gleason grading score along with Digital Rectal Exam (DRE) and Prostate Specific Antigen (PSA) levels in the blood are the method of choice for prostate cancer grading and along with the TNM staging system gives comprehensive information about the prostate cancer patient. It should be remembered that grading and staging are not the same, but both combined have great potential in defining the correct treatment regimen and prognostic outcome.
DRE can reveal the location of the tumor in the prostate and additionally define whether it is present on one or both sides of the prostate gland. PSA levels are used as confirmatory test for observations made during DRE. Most physician do an overall body examination as it tends to give them a fair idea about the stage of the disease based on symptoms (like bone pain might suggest that the cancer has spread to the bone). In the Gleason grading system the two largest areas of the cancer are picked and assigned an arbitrary value ranging from 1 to 5 (5 being the most aggressive). The two grades are subsequently added to produce a composite Gleason score. Gleason score upto 4 is considered low grade, between 5 and 7 are intermediates and those above 7 are considered high grade (most aggressive).
A} T categories. T1 to T4 are used to define the local occurrence of the tumor and is normally done using clinical examination by the attending physician.Each stage has further sub-stages as described in this text.
T1: The tumor is neither felt during DRE nor observed during transrectal ultrasound (TRUS).
- T1a: Accidental discovery of the tumor during transurethral resection of the prostate (TURP) performed to check for benign prostatic hyperplasia (BPH; a non-cancerous inflammatory condition of the prostate) and the tumor masks less than 5% of the tissue surface area.
- T1b: Discovery as in T1a, but the tumor covers greater than 5% of the tissue surface area.
- T1c: Discovery of the tumor is made only through fine needle biopsy that was done as a confirmatory measure after detecting high serum PSA levels.
T2: Tumor is felt during DRE, but is limited to the prostate gland.
- T2a: The tumor covers one-half or less of the prostate gland area on one of the two sides.
- T2b: The tumor is still on one side only, but covers more than one-half of the prostate gland.
- T2c: The tumor is present on both sides of the prostate gland.
T3: The tumor is not limited to the prostate and can possibly be found in adjacent seminal vesicles.
- T3a: The tumor has grown beyond the prostate, but still not found in the seminal vesicles.
- T3b: The tumor can be located in the seminal vesicles.
T4: The tumor has grown into the adjacent urethral sphincter, the wall of the pelvis and the rectum.
B} N categories. This is fairly straightforward and used to define whether the cancer cells are present in adjacent lymph nodes, points from where they will start migrating to other tissues.
N0: The cancer cells have not spread to any lymph nodes.
N1: The cancer cells have spread to regional lymph nodes in the pelvic region.
C} M categories. This is used to define whether the cancer cells from the primary tumor in the prostate gland have disseminated to the lymphatic circulation and spread (METASTASIS) to other organs to initiate secondary tumors. Very important for delineating advanced disease stages and fine tuning aggressive management.
M0: The cancer cells have not spread outwards of the lymph nodes. No metastasis.
M1: Cancer cells have disseminated to the lymphatic circulation.
- M1a: The cancer cells have just entered the lymphatic circulation and have been routed to secondary sites outside the pelvic region.
- M1b: The prostate cancer cells have formed a secondary site of infestation in the bones.
- M1c: The prostate cancer cells have metastasized to other secondary organs (lungs, liver, or brain). This happens independently and alongside of cells metastasizing to the bones.
For a more comprehensive view-point, the T, N, and M staging information is combined with the Gleason score, and PSA serum levels and this process is termed as the stage grouping. The overall stage is expressed in Roman numerical from I through IV (I being the least aggressive and IV being the most aggressive). Based on this stage grouping, the treatment regimen is finally decided and prognostic classification of the patient is predicted.