Prostate cancer staging

Prostate cancer staging is the process by which physicians categorize the risk of cancer having spread beyond the prostate, or equivalently, the probability of being cured with local therapies such as surgery or radiation. Once patients are placed in prognostic categories, this information can contribute to the selection of an optimal approach to treatment. Prostate cancer stage can be assessed by either clinical or pathological staging methods. Clinical staging usually occurs before the first treatment and tumour presence is determined through imaging and rectal examination, while pathological staging is done after treatment once a biopsy is performed or the prostate is removed by looking at the cell types within the sample. There are two schemes commonly used to stage prostate cancer in the United States. The most common is promulgated by the American Joint Committee on Cancer (AJCC), and is known as the TNM system, which evaluates the size of the tumor, the extent of involved lymph nodes, and any metastasis (distant spread) and also takes into account cancer grade. As with many other cancers, these are often grouped into four stages (I–IV). Another scheme that was used in the past was Whitmore-Jewett staging, although TNM staging is more common in modern practice. In the United Kingdom, the 5-tiered Cambridge Prognostic Group (CPG) is used, replacing a previous system that divided prostate cancer into three risk groups.

TNM staging

From the AJCC 7th edition and UICC 7th edition. Stage I disease is cancer that is found incidentally in a small part of the sample when prostate tissue is removed for other reasons, such as benign prostatic hyperplasia, and the cells closely resemble normal cells and the gland feels normal to the examining finger. In Stage II more of the prostate is involved and a lump can be felt within the gland. In Stage III, the tumor has spread through the prostatic capsule and the lump can be felt on the surface of the gland. In Stage IV disease, the tumor has invaded nearby structures or has spread to lymph nodes or other organs. The Gleason Grading System is based on cellular content and tissue architecture from biopsies, which provides an estimate of the destructive potential and ultimate prognosis of the disease.

Evaluation of the (primary) tumor ('T')

Clinical T stage (cT) cTX: cannot evaluate the primary tumor cT0: no evidence of tumor cT1: tumor present, but not detectable clinically or with imaging cT1a: tumor was incidentally found in 5% or less of prostate tissue resected (for other reasons) cT1b: tumor was incidentally found in greater than 5% of prostate tissue resected cT1c: tumor was found in a needle biopsy performed due to an elevated serum PSA cT2: the tumor can be felt (palpated) on examination, but has not spread outside the prostate cT2a: the tumor is in half or less than half of one of the prostate gland's two lobes cT2b: the tumor is in more than half of one lobe, but not both cT2c: the tumor is in both lobes but within the prostatic capsule

cT3: the tumor has spread through the prostatic capsule (if it is only part-way through, it is still T2) cT3a: the tumor has spread through the capsule on one or both sides cT3b: the tumor has invaded one or both seminal vesicles cT4: the tumor has invaded other nearby structures It should be stressed that the designation "T2c" implies a tumor which is palpable in both lobes of the prostate. Tumors which are found to be bilateral on biopsy only but which are not palpable bilaterally should not be staged as T2c.

Pathological T stage (pT) pT2: organ confined pT2a: unilateral, one-half of one side or less pT2b: unilateral, involving more than one-half of side, but not both sides pT2c: bilateral disease pT3: extraprostatic extension pT3a: extraprostatic extension or microscopic invasion of bladder neck pT3b: seminal vesicle invasion pT4: invasion of rectum, levator muscles, and/or pelvic wall

Evaluation of the regional lymph nodes ('N') NX: cannot evaluate the regional lymph nodes N0: there has been no spread to the regional lymph nodes N1: there has been spread to the regional lymph nodes

Evaluation of distant metastasis ('M') MX: cannot evaluate distant metastasis M0: there is no distant metastasis M1: there is distant metastasis M1a: the cancer has spread to lymph nodes beyond the regional ones M1b: the cancer has spread to bone M1c: the cancer has spread to other sites (regardless of bone involvement)

Evaluation of the histologic grade ('G')

Usually, the grade of the cancer (how different the tissue is from normal tissue) is evaluated separately from the stage. For prostate cancer, cell morphology is graded based on the Gleason grading system. Of note, this system of describing tumors as "well-", "moderately-", and "poorly-" differentiated based on Gleason score of 2–4, 5–6, and 7–10, respectively, persists in SEER and other databases but is generally outdated. In recent years pathologists rarely assign a tumor a grade less than 3, particularly in biopsy tissue.

Grade Group classification ('GG') A more contemporary reporting standard includes the Grade Groups. For prostate cancer, grade group information and prostate-specific antigen levels are used in conjunction with TNM status to group cases into four overall stages.

Grade Group 1 = Gleason 6 (or less) Grade Group 2 = Gleason 3+4=7 Grade Group 3 = Gleason 4+3=7 Grade Group 4 = Gleason 8 Grade Group 5 = Gleason 9-10

Overall staging In the AJCC (2018) staging system, the tumor, lymph node, metastasis, Gleason grade grouping and Prostate-specific antigen status can be combined into four stages of worsening severity.

Whitmore-Jewett staging Although it is no longer commonly used in practice, the Whitmore-Jewett system (also known as ABCD rating) is similar to the TNM system and has approximately equivalent stages. Roman numerals are sometimes used instead of Latin letters for the overall stages (for example, Stage I for Stage A, Stage II for Stage B, and so on).

… excerpt ends here. Continue reading the full article.