What is prostate cancer staging?
By staging your cancer, your doctor is trying to assess, based on your prostate biopsy results, your physical examination, your PSA, and other tests and X-rays (if obtained), whether your prostate cancer is confined to the prostate, and if it is not, to what extent it has spread. Studies of large numbers of men who have undergone radical prostatectomy and pelvic lymph node dissections have provided for the development of nomograms predicting the pathologic stage of CaP based on clinical stage (TNM), PSA, and Gleason score (Table 5). It was initially thought that magnetic resonance imaging (MRI) would be very helpful in determining whether capsular penetration and extracapsular disease were present; however, it has only proved to be useful in centers that perform large numbers of MRIs. Similarly, the use of computed tomographic (CT) scanning in assessing whether or not the cancer has spread to the pelvic lymph nodes has been disappointing.
Knowing the stage (the size and the extent of spread) of the prostate cancer helps the doctor counsel you on treatment options. Your doctor may tell you a clinical stage (Figure 8), based on your rectal examination, prostate biopsies, and radiographic/nuclear medicine studies (CT scan, bone scan, MRI). Pathological staging is performed when a pathologist examines the prostate, seminal vesicles, and pelvic lymph nodes (if removed) at the time of radical prostatectomy. The most common staging system used is called the TNM System. In this system, T refers to the size of the tumor in the prostate, N refers to the extent of cancerous involvement of the lymph nodes, and M refers to the presence or absence of metastases (deposits of prostate cancer outside of the
Table 5. Nomograms Predicting Pathologic Stage of CaP Based on Clinical Stage (TNM), PSA, and Gleason Score
Makarov DV, Trock BJ, Humphreys EB, Mangold LA, Walsh PC, Epstein JI, Partin AW. Updated nomogram to predict pathologic stage of prostate cancer given prostate-specific antigen level, clinical stage, and biopsy gleason score (partin tables) based on cases from 2000 to 2005. Urology 2007; 69: 1095—1101.
Figure 8. The prostate gland showing the different stages of cancer.
prostate and lymph nodes). Another staging system is the Whitmore Jewett System (Table 6).
In individuals in whom there is a concern about metastases to the bone, such as those with high PSAs and pain localized to a bone, a bone scan may be obtained to determined if there are bone metastases.
A bone scan is a study performed in the nuclear medicine department that involves injecting a small amount of a radioactive chemical through a vein into your bloodstream. The chemical circulates through your body and is picked up by areas of fast bone growth that may be associated with cancer. The bone scan is the most sensitive technique currently available for identifying prostate cancer that has spread to the bones. Other problems of
Table 6. Prostate Cancer Staging Systems
*None, No comparable category; TUR, Transurethral resection; PSA, prostate-specific antigen.
Source: Loughlin, P. 100 Questions and Answers About Prostate Disease. Jones and Bartlett Publishers, LLC, 20(
the bones, such as a history of a broken bone, arthritis, and Paget's disease, may cause an increase in uptake of the radioactive chemical. Often, your history, the location of the bone, and possible additional studies, such as a plain X-ray study or an MRI, will help determine whether the area of increased uptake indicates the presence of cancer.
The bone scan is quite sensitive, but it does not identify small numbers of cancer cells in the bones. In a small number of men (8%), the bone scan may be normal when bone metastases are present. Prostate cancer is not the only cancer that spreads to the bone, but prostate cancer tends to cause the bone to look different than that of involvement with other cancers, such as breast, colon, and bladder. Prostate cancer metastases are typically osteoblastic, whereas those of other cancers tend to be osteolytic. Osteoblastic lesions look as if there is an increase in the amount of bone present on a plain X-ray, whereas osteolytic lesions look like there is a loss of bone. The bone scan may also show obstruction of the urinary tract, leading to hydronephrosis.
The bone scan is often obtained as part of the staging work-up in men with prostate cancer and is helpful in men with a rising PSA (either after primary treatment, such as radical prostatectomy, or during watchful waiting) with or without bone pain to identify new areas of uptake that may indicate new bone involvement. The bone scan is usually obtained as part of the staging evaluation in men with newly diagnosed clinically localized prostate cancer who have a PSA > 20 ng/mL. Because the risk of bone metastases in men with newly diagnosed clinically localized prostate cancer who have a PSA < 20 ng/mL is so low, a bone scan is not routinely obtained in these men. Although the chemical used for the study is radioactive, the amount used is small, and it will not put you or your family at-risk.