An overview of risk groups for NMIBC

Non-muscle invasive bladder cancer (NMIBC) is a type of cancer that begins in the inner lining of the bladder, a hollow organ that stores urine. “Non-muscle invasive” means the cancer has not spread into the thick muscle layer of the bladder wall. NMIBC is the most common classification of bladder cancer, and over 75 percent of all newly diagnosed bladder cancers are NMIBC.

NMIBC is also categorized as low-risk, intermediate-risk, and high-risk depending on how likely the cancer is to become muscle invasive and how likely it is to recur after treatment. In general, NMIBC has a high rate of recurrence, and reducing the chances of recurrence is an important focus of treatment. Also, due to the high rate of recurrence, follow-up care and monitoring after treatment are essential in all cases.

Here is a look at how risk categories are determined and what they mean for treatment.

TURBT and biopsy

Treatment for NMIBC typically begins with a procedure called transurethral resection of bladder tumor (TURBT). This is a type of minimally invasive surgery where a surgeon will remove the tumor or tumors in the bladder. TURBT is typically followed by additional steps to help prevent the cancer from growing or returning—destroying remaining cancer cells with electricity, high-energy lasers, or anti-cancer drugs that are delivered directly into the bladder (intravesical therapy).

While TURBT is an initial treatment, it is also an essential part of the diagnostic process. TURBT is also used to biopsy the cancer growing in the bladder. Biopsy is the removal of a tissue for study in a lab, which is performed by a healthcare provider called a pathologist. Biopsy is one of the best tools that healthcare providers have to learn about a cancer and how that cancer is behaving. In the treatment of bladder cancer, this information can be critical when deciding on the next steps in treatment.

NMIBC risk groups

NMIBC is often assigned a risk group. A risk group is different from the stage of the cancer. Stage refers to the size of the cancer and how far it has spread, usually given as stages 0 to IV.

In the treatment of bladder cancer, risk groups are only assigned for NMIBC, and are therefore only assigned to stage 0 and I bladder cancers (stage II and above are all muscle invasive).

Factors a healthcare team will consider when assigning a risk group

• The size of the tumor or tumors
• The number of tumors
• How far the tumor has grown into the bladder wall (how close it is to the muscle layer)
• The cancer grade (how abnormal the cancer cells are compared to normal cells)
• If the cancer is a recurrence
• The subtype of bladder cancer (less common subtypes like squamous cell carcinoma and adenocarcinoma tend to be aggressive)

Other factors that can be considered

There are also other factors about a person’s personal and medical history that are considered high-risk factors for bladder cancer, and these may be considered when assigning a risk group:

• The age of the person with bladder cancer (older age is associated with higher risk)
• If the person with bladder cancer is male
• History of smoking
• A family history of bladder cancer or hereditary cancer syndromes (Lynch syndrome, Peutz-Jeghers syndrome, or Cowden syndrome
• Presence of blood in the urine with urinalysis (and the amount of blood)
• Having had a urethral catheter in place for a month or longer
• History of chemotherapy treatment or radiation treatment in pelvic region
• History of exposure to toxic chemicals

Examples of low, intermediate, and high risk

• A single small, low-grade tumor may be considered low risk.
• Multiple or large slow-growing tumors, a cancer that has recurred within a year, or a single, small, fast-growing tumor may be considered intermediate risk.
• Multiple or large high-grade tumors or larger fast-growing tumors may be considered high risk.
• Additionally, some NMIBC may be considered very high risk if the cancer does not respond to treatment, recurs in the urethra, or if cancer cells are detected in the blood or lymph system near the tumor.

As mentioned above, risk helps a healthcare team predict how likely the cancer is to become muscle invasive or recur after treatment—important considerations when making decisions about treatment. For example, a person with low-risk NMIBC may only receive intravesical therapy once shortly after TURBT, while a person with high-risk NMIBC may receive intravesical therapy regularly for several years.

Keep in mind that these are all simplified explanations, and that these are only examples and not a comprehensive list. NMIBC and risk group are complex topics that are best explained by a healthcare provider.