The co-authors of Invasion of the Prostate Snatchers, blog alternate posts weekly. We invite you to post your comments.

Tuesday, September 27, 2011

Making Sense of the TNM Staging System


In my last Blog I described the Gleason grading system, which urologists use to establish the aggressiveness of your cancer based on the pathologist’s analysis of your biopsy. If you are requesting copies of all your medical records (as you should) you may come across a tumor  staging code called the Tumor Node Metastasis (TNM) staging system.  This code is used to describe to doctors information about whether your prostate cancer is localized, regional, or advanced.

The letter “T” in the TNM system refers to the tumor.  Your doctor “stages” the tumor based on how big the tumor nodule feels when he does a digital rectal examination.  For example, information about size, on whether it is in one or both sides of the prostate, and on whether it has gone outside the prostate is communicated by the four categories—T1, T2, T3, and T4.

Subtypes of T1 (T1, T1a, T1b, T1c) or T2 (T2, T2a, T2b, T2c) refer to localized cancer, meaning the cancer has not spread beyond the prostate. Any of the T3 subtypes (T3a, T3b) refer to regional cancer, which means that the cancer extends just outside the prostate and may have gone into the seminal vesicles. T4 has only one category, and refers to cancer that has spread to the bladder and/or to other adjacent areas of the pelvis.

The “N” in the TNM code refers to whether the cancer has spread to the lymph nodes in the pelvis. N0 means it has not spread to the pelvic nodes; N1 indicates that it has spread. If the cancer has spread to the pelvic nodes, it is more likely to move beyond the nodes and into other parts of the body, making it harder to treat.

The “M” in the TNM staging system refers to whether the tumor has spread or metastasized beyond the lymph nodes in the pelvis. M0 means zero metastasis. M1a means the cancer has spread into the lymph nodes beyond the pelvic area. M1b refers to cancer that has spread to the bones. M1c means the cancer has spread beyond the lymph nodes and bones to other parts of the body.

At the initial staging of the cancer, your urologist first performs a digital rectal examination to determine the presence and status of the tumor. If he determines that the cancer is at a very low level perhaps he will not order further tests. But if he suspects that the cancer may have spread outside the prostate gland, he will order a CT scan, an MRI, or bone scan. Cautious or conservative doctors are likely to order all three of these imaging tests regardless of their findings in the DRE. So don’t assume that you may have advanced cancer just because your doctor sends you for a CT scan or MRI.

I realize that all this information is somewhat confusing (It begins to sound like loony runaway variations on the British Secret Service MI5, MI6, SIS and Lord knows what else). However, the fact remains that, by grouping your PSA level, Gleason grade, and TNM stage, your urologist can determine your prostate cancer’s risk level and advise you on your best treatment options.

Bottom line, the more you know the better.  Yours is really the decision that counts so you have to understand what is going on.  You can obtain more information about staging on the PCRI's blue community website at

No comments: