What is bladder cancer?
To understand bladder cancer, it helps to know about the normal structure and function of the bladder.
The normal bladder
The bladder is a hollow organ in the pelvis with flexible, muscular walls. Its main function is to store urine before it leaves the body. The average adult bladder holds about 2 cups of urine. Urine is made by the kidneys and is then carried to the bladder through tubes called ureters.
When you urinate, the muscles in the bladder contract, and urine is forced out of the bladder through a tube called the urethra. In women, the urethra is very short and opens just in front of the vagina. In men, the urethra is longer. It passes through the prostate gland and the penis, and opens at the tip of the penis.
The wall of the bladder has 4 main layers.
- The innermost lining is made up of cells calledurothelial or transitional cells, so this layer is called theurothelium or transitional epithelium.
- Beneath the urothelium is a thin layer of connective tissue, blood vessels, and nerves, which is called thelamina propria.
- Next is a thick layer of muscle called themuscularis propria.
- Outside of this muscle, a layer of fatty connective tissue separates the bladder from other nearby organs.
Knowing about these layers is important in understanding how bladder cancer grows. Most bladder cancers start in the urothelium. As the cancer grows into or through the other layers in the bladder, it becomes more advanced and harder to treat.
Types of bladder cancer
Bladder cancers are divided into several types based how their cells look under a microscope. Different types can respond differently to treatments.
Transitional cell (urothelial) carcinoma
This is by far the most common type of bladder cancer. More than 9 out of 10 bladder cancers are this type. The cells from transitional cell carcinomas (TCCs) look like the urothelial cells that line the inside of the bladder.
Urothelial cells also line other parts of the urinary tract, such as the lining of the kidneys (called the renal pelvis), the ureters, and the urethra, so TCCs can also occur in these places. In fact, patients with bladder cancer sometimes have other tumors in the lining of the kidneys, ureters, or urethra. If someone has a cancer in one part of their urinary system, the entire urinary tract needs to be checked for tumors.
Bladder cancers are often described based on how far they have invaded into the wall of the bladder:
- Non-invasive bladder cancers are still in the inner layer of cells (the transitional epithelium) but have not grown into the deeper layers.
- Invasive cancers grow into the lamina propria or even deeper into the muscle layer. Invasive cancers are more likely to spread and are harder to treat.
A bladder cancer can also be described as superficial or non-muscle invasive. These terms include both non-invasive tumors as well as any invasive tumors that have not grown into the main muscle layer of the bladder.
Transitional cell carcinomas are also divided into 2 subtypes, papillary and flat, based on how they grow (see image above).
- Papillary carcinomas grow in slender, finger-like projections from the inner surface of the bladder toward the hollow center. Papillary tumors often grow toward the center of the bladder without growing into the deeper bladder layers. These tumors are called non-invasive papillary cancers. Very low-grade, non-invasive papillary cancer is sometimes called papillary neoplasm of low-malignant potential and tends to have a very good outcome.
- Flat carcinomas do not grow toward the hollow part of the bladder at all. If a flat tumor is only in the inner layer of bladder cells, it is known as a non-invasive flat carcinoma or a flat carcinoma in situ (CIS).
If either a papillary or flat tumor grows into deeper layers of the bladder, it is called an invasive transitional cell (or urothelial) carcinoma.
Other cancers that start in the bladder
Several other types of cancer can start in the bladder, but these are all much less common than transitional cell (urothelial) cancer.
Squamous cell carcinoma: In the United States, only about 1% to 2% of bladder cancers are squamous cell carcinomas. Under a microscope, the cells look much like the flat cells that are found on the surface of the skin. Nearly all squamous cell carcinomas are invasive.
Adenocarcinoma: Only about 1% of bladder cancers are adenocarcinomas. The cancer cells have a lot in common with gland-forming cells of colon cancers. Nearly all adenocarcinomas of the bladder are invasive.
Small cell carcinoma: Less than 1% of bladder cancers are small-cell carcinomas, which start in nerve-like cells called neuroendocrine cells. These cancers often grow quickly and typically need to be treated with chemotherapy like that used for small cell carcinoma of the lung.
Sarcoma: Sarcomas start in the muscle cells of the bladder, but they are rare. These less common types of bladder cancer (other than sarcoma) are treated similar to transitional cell cancers, especially for early stage tumors, but different drugs may be needed if chemotherapy is required.
The rest of this document focuses on transitional cell (urothelial) cancers of the bladder.
What are the key statistics about bladder cancer?
The American Cancer Society’s estimates for bladder cancer in the United States for 2015 are:
- About 74,000 new cases of bladder cancer diagnosed (about 56,320 in men and 17,680 in women).
- About 16,000 deaths from bladder cancer (about 11,510 in men and 4,490 in women).
The rates of new cancers and of cancer deaths and have been dropping slightly in women in recent years. In men, incidence rates have been decreasing and death rates have been stable. More than 500,000 people in the United States are bladder cancer survivors.
Bladder cancer occurs mainly in older people. About 9 out of 10 people with this cancer are over the age of 55. The average age at the time of diagnosis is 73.
Men are about 3 to 4 times more likely to get bladder cancer during their lifetime than women. Overall, the chance men will develop this cancer during their life is about 1 in 26. For women, the chance is about 1 in 90. Bladder cancer is the fourth most common cancer in men. Whites are diagnosed with bladder cancer almost twice as often as blacks.
In about half of all cases, patients are first diagnosed with bladder cancer while it is still confined to the inner layer of the bladder (non-invasive or in situ cancer). About 35% have bladder cancer that has invaded into deeper layers but is still contained in the bladder. In most of the remaining cases, the cancer has spread to nearby tissues outside the bladder. Rarely (in about 4% of cases), it has spread to distant sites. Black patients are slightly more likely to have more advanced disease when they are diagnosed, compared to whites.
How is bladder cancer treated?
General treatment information
Once your cancer has been diagnosed and staged, there is a lot to think about before you and your doctor choose a treatment plan. You may feel that you must make a decision quickly, but it is important to give yourself time to absorb the information you have just learned. Ask your cancer care team questions.
You will want to weigh the benefits of each treatment option against the possible risks and side effects. The best treatment for you will depend on the type and stage of your bladder cancer as well as your general health, age, and personal preferences.
If time permits, you might want to get a second opinion about your best treatment option. This can be especially helpful if you have several treatment choices. A second opinion can provide more information and help you feel more confident about the treatment plan you choose.
The main types of treatment for cancer of the bladder are:
- Intravesical therapy
- Radiation therapy
Sometimes, more than one of type of treatment might be used. Surgery, alone or with other treatments, is used in nearly all cases.
Surgery can often remove early stage bladder tumors. But a major concern in people with early-stage bladder cancer is that new cancers often form in other parts of the bladder over time. Removing the entire bladder (known as a radical cystectomy) is one way to avoid this, but it can have major side effects. If the entire bladder is not removed, other treatments may be given to try to reduce the risk of new cancers. Whether or not other treatments are given, close follow-up is needed to look for signs of new cancers in the bladder.
Depending on your options, you can have different types of doctors on your treatment team. The types of doctors who treat bladder cancers include:
- Urologists: surgeons who specialize in treating diseases of the urinary system and male reproductive system
- Radiation oncologists: doctors who treat cancer with radiation therapy
- Medical oncologists: doctors who treat cancer with medicines such as chemotherapy
Other specialists might be part of your treatment team as well, including physician assistants, nurse practitioners, nurses, psychologists, social workers, rehabilitation specialists, and other health professionals.