The TNM (tumor, nodes, metastasis) staging system is used to describe prostate cancer’s clinical stage, or how far it has spread (metastasized), and helps determine appropriate treatment options.
The staging system assigns a T number (T1 to T4) to describe the extent of the tumor as felt during a digital rectal exam. The N number (N0 to N1) indicates whether the cancer has spread to any lymph nodes, and the M number (M0 to M1) indicates the presence or absence of metastasis (spread to distant sites). The T and M designations are divided into subcategories (designated a, b, and c) that provide further detail on the extent of the cancer. Here’s what each stage means:
The tumor cannot be felt during the digital rectal exam or seen with diagnostic imaging.
• T1a: Tumor found incidentally during surgery for benign prostatic hyperplasia (BPH) and is present in less than 5 percent of removed tissue.
• T1b: Tumor found incidentally during BPH surgery but involves more than 5 percent of removed tissue.
• T1c: Tumor found during needle biopsy for elevated prostate-specific antigen (PSA).
The tumor can be felt during the digital rectal exam but is believed to be confined to the gland.
• T2a: Tumor involves one-half or less of one side of the prostate.
• T2b: Tumor involves more than one-half of one side but not both sides.
• T2c: Tumor involves both sides of the prostate.
The tumor extends through the prostate capsule and may involve the seminal vesicles.
• T3a: Tumor extends through the capsule but does not involve the seminal vesicles.
• T3b: Tumor has spread to the seminal vesicles.
The tumor has invaded adjacent structures (other than the seminal vesicles), such as the bladder neck, rectum or pelvic wall.
Cancer has not spread to any lymph nodes.
Cancer has spread to one or more regional lymph nodes (nodes in the pelvic region).
There is no distant metastasis.
There is distant metastasis.
• M1a: Cancer has spread to distant lymph nodes.
• M1b: Cancer has spread to the bones.
• M1c: Cancer has spread to other organs, with or without bone involvement.