Bladder cancer develops in the tissues of the urinary bladder, an organ located in the front of the pelvis that collects and stores urine. The bladder consists of elastic tissue that contains a muscular layer and forms a sac. The lining of the bladder is composed of tall, thin cells called transitional cells, which form a protective layer to prevent urine from penetrating underlying bladder tissue. The majority of bladder cancers form in these transitional cells and then may grow into the wall of the bladder.
Bladder cancers are named for the cells where they originate, so cancers that form in the lining of the bladder are called transitional cell or urothlial carcinomas. Less commonly occurring bladder cancers are called squamous cell carcinomas, adenocarcinomas, and small cell carcinomas. Bladder cancers are also distinguished by whether they are limited to the bladder or have spread to other organs. Bladder cancers that have spread to other organs are termed “invasive.”
Bladder cancer is the most frequently occurring cancer of the urinary tract. In the United States, it is the fourth most common cancer in men and the ninth most common cancer in women. The frequency of bladder cancer increases with advancing age and 80% of patients diagnosed with bladder cancer are between the ages of 50 and 80. Seventy percent of bladder cancers in men and 75% of bladder cancers in women occur in those over age 65. Men are more likely than women to be diagnosed with bladder cancer. One in thirty men are diagnosed with bladder cancer compared to one in ninety women. Men also are more likely to die from the disease than are women.
Bladder cancer is diagnosed more frequently in whites than in African Americans, Hispanics, Asians, and Pacific Islanders. Although fewer African Americans than whites are diagnosed with bladder cancer, more African Americans die from the disease because they are diagnosed at later states, after the disease has progressed and is less likely to be treated successfully.
Causes and symptoms
Chronic irritation of the lining of the bladder can produce inflammation, and the bladder liningmay, over time, change from transitional cells to squamous cells, which are similar to skin cells. These changes occur because the cells lining the bladder change in an effort to protect the bladder from the source of irritation. In many cases, especially in developing countries, parasites, such as schistosomiasis (also known as trematode worms or flukes), are the source of the parasitic irritation. Inflammation also may occur in response to exposure to carcinogens (cancer-causing substances) such as benzidine or tobacco or as a result of mechanical irritation from chronic infection, catheter use, or bladder stones (accumulations of minerals that form small, hard stones). Spinal cord injury also is associated with increased risk of developing bladder cancer.
Although many cases of bladder cancer occur without any symptoms, possible signs of bladder cancer include blood in the urine, frequent or painful urination or urgency, and low back pain .
Like most other cancers, early detection and diagnosis of bladder cancers improves the likelihood that treatment is successful. Persons at increased risk of developing bladder cancer such as workers exposed to certain carcinogenic chemicals or those with other kinds of bladder disorders may be screened (tested before symptoms of the disease appear) for bladder cancer. Screening for bladder cancer may involve urine cytology, a test in which urine cells are “washed” and then examined under a microscope to see if precancerous or cancerous cells are present. Cytoscopy, inspection of the interior of the bladder with a cytoscope, a long, thin tube with a light and lens, also may be used to screen for bladder cancer. Using cytoscopy, a physician also may perform a biopsy, removing a sample of bladder tissue for examination under a microscope.
QUESTIONS TO ASK YOUR DOCTOR
- What is the stage and grade of the bladder cancer? What is the cell type?
- What is the likelihood that the cancer has spread?
- Based on the stage and grade of the bladder cancer, what are the treatment options?
- What are the benefits and risks of the different treatment options?
- What are the chances of a recurrence of the bladder cancer?
- What is the prognosis after treatment?
Along with the physical examination, the patient's medical history can help to determine the need for diagnostic tests for bladder cancer. For example, a history of blood in the urine or changes in bladder habits may be signs of bladder cancer. Other diagnostic tests that may be performed include urine culture , in which a sample of urine is sent to the laboratory to determine whether infection is present. Imaging studies such as computed tomography (CT) scans and magnetic resonance imaging (MRI) help physicians to visualize the bladder and nearby structures. An intravenous pyelogram (IVP), an x-ray study of the kidneys, ureters, and bladder taken after injection of a dye into a blood vessel, enables identification of cancer and can help to determine whether the cancer has spread beyond the bladder.
Bladder cancer biomarker studies also may be performed. These tests detect substances released by bladder cancer cells into the urine. Specific bladder tumor marker studies also may be used in combination with cytology to detect recurrences (cases when previously treated bladder cancer returns) of bladder cancers.
Bladder cancers are graded, or staged, based on their virulence and the extent to which they are different from adjacent bladder tissue. Stage 0 describes tumors limited to the lining of the bladder. Stage I tumors extend through the bladder lining but do not penetrate the muscle. Stage II tumors have invaded the bladder's muscle layer and stage III tumors have spread beyond the bladder. At the time of diagnosis, about one-third of cases are noninvasive, one-third are minimally invasive, and another third are more deeply invasive.
Treatment for bladder cancer depends on several factors, including its stage;, however, it usually involves some form of surgery. Treatment also may entail use of one or more additional therapies such as chemotherapy , radiation therapy, and biologic therapy. Several types of surgery may be performed, including the following:
- Transurethral resection (TUR) involves insertion of a cytoscope through the urethra (the tube that transports urine from the bladder) into the bladder to remove the cancer or to introduce high-energy electricity to burn and destroy the tumor.
- Segmental cystectomy is surgery to remove the cancer and part of the bladder surrounding it.
- Radical cystectomy is surgical removal of the bladder and any lymph nodes or adjacent organs that contain cancer cells. In men, the prostate and seminal vesicles are removed; in women, the uterus, ovaries, fallopian tubes and part of the vagina are removed.
Chemotherapy is drug treatment to combat cancer. It is used for early stage disease and invasive cancers that have spread beyond the bladder. It may be given before surgery and after surgery, or only following surgical removal of the tumor. For stage 0 and I cancers, chemotherapy is often administered directly into the bladder. Later stage cancers are generally treated with intravenous chemotherapy, which travels throughout the body. Chemotherapeutic regimens vary; some are single drug and others combine two or more drugs. Drugs commonly used to treat bladder cancer include:
Biomarker —A molecule found in blood, urine, or other body fluids, that is a of a condition or disease. A biomarker also may be used to monitor the progress of treatment for a disease or condition.
Carcinogen —Any substance that causes cancer.
Cystectomy —Surgery to remove all or part of the bladder.
Cytology —Examination of cells using a microscope.
Cytoscopy —Examination of the bladder and urethra using a cystoscope, a long, thin tube with a light and lens that is inserted into the urethra. A cytoscope may have a tool attached for removing tissue for examination under a microscope.
Another approach to treatment is biologic or immunotherapy therapy, which aims to help the patient's own immune system mount an attack against the cancer. For bladder cancer, this approach involves introducing a solution of genetically modified tuberculosis bacteria (Bacille Calmette-Guerin or BCG) into the bladder through a catheter.
Photodynamic therapy, treatment that uses a combination of a drug and laser light to kill cancer cells, is newer treatment that is being tested as of 2008 in clinical trials to determine its effectiveness. One advantage of this therapy is that it targets cancer cells and poses little risk to healthy tissue.
The chance of recovery depends on the stage of the bladder cancer—like other cancers, in early stages it is more likely to be cured. The prognosis also depends on the age and general health of the patient and the type of bladder cancer cells present in the tumor. Because there is a high risk of recurrence, patients with bladder cancer are closely monitored after they complete treatment.
Preventing bladder cancer focuses on reducing risk. Some of the known risk factors include:
- exposure to cancer-causing chemicals or substances
- consuming a diet high in fried meats and fat
- parasitic infection or other chronic bladder infections
In addition to avoiding known risk factors, persons at high risk of developing bladder cancer and those at risk for recurrence may be candidates for chemoprevention. Chemoprevention is the use of specific drugs, vitamins , or other substances to reduce the risk of developing cancer or to prevent its recurrence. Clinical trials of chemoprevention agents for bladder cancer were underway as of 2008.
Abeloff, Martin D., et al. Clinical Oncology, 3rd ed. Living-stone, Edinburgh, Scotland: Churchill Livingston, 2004. See esp. chap. 86, “Carcinoma of the Bladder.”
“A Snapshot of Bladder Cancer.” National Cancer Institute. December 2007 [cited March 16, 2008]. http://planning.cancer.gov/disease/Bladder-Snapshot.pdf
“Overview Bladder Cancer: What Is Bladder Cancer?” American Cancer Society. December 1, 2006 [cited March 16, 2008]. http://www.cancer.org/docroot/CRI/content/CRI_2_2_1X_What_is_bladder_cancer_44.asp?sitearea=
Barbara Wexler MPH