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 long, thin cells called transitional cells, which form a protective layer to prevent urine from penetrating underlying bladder tissue. The majority of bladder cancers arise in these transitional cells and then may grow into the wall of the bladder.
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; 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 30 men is diagnosed with bladder cancer compared with one in 90 women. Men also are more likely to die from the disease than are women.
Bladder cancer is diagnosed more often in Caucasians than in African Americans, 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 stages, after the disease has progressed and is less likely to be treated successfully.
Bladder cancers are named for the cells where they originate. Cancers that arise in the lining of the bladder are called transitional cell carcinomas or urothelial carcinomas. Less commonly occurring bladder cancers are 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.”
Chronic irritation of the lining of the bladder can produce inflammation, and the bladder lining may, over time, change from transitional cells to squamous cells, which are similar to skin cells. These changes take place when the cells lining the bladder alter in an effort to protect the bladder from the source of irritation. In many cases (especially in developing countries), parasites, such as worms of the Schistosoma type (also known as trematode worms or flukes), are the most common source of parasitic irritation. Inflammation also may occur in response to exposure to carcinogens (cancer-causing substances), such as benzidine or those present in 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 have no symptoms, possible signs of bladder cancer include blood in the urine, frequent or painful urination or urge to urinate, and lower back pain.
As with most other cancers, early detection and diagnosis of bladder cancers improve the likelihood that treatment will be successful. Persons at increased risk of 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 the disease. Screening for bladder cancer may involve urine cytology study, a test in which urine cells are “washed” and then examined under a microscope to see if precancerous or cancerous cells are present. Cystoscopy, inspection of the interior of the bladder with a cystoscope, a long, thin tube with a light and lens, also may be used to screen for bladder cancer. Using cystoscopy, a physician also may perform a biopsy, removing a sample of bladder tissue for examination under a microscope.
Along with the physical examination, the patient's medical history can help 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 scans and magnetic resonanc imaging help physicians picture the bladder and nearby structures. An intravenous pyelogram, 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 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 cytologic study to detect recurrences (cases when previously treated disease 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 and the clinical factors that indicate whether the patient is at high or low risk of recurrence. Treatment usually involves some form of surgery, and it may also entail use of one or more additional therapies, such as chemotherapy, radiation therapy, and biologic therapy. Several types of surgery may be performed.
Transurethral resection calls for insertion of a cystoscope 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 removes the cancer and part of the bladder surrounding it.
Radical cystectomy removes 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. This form of treatment is known as intravesical (“into the bladder”) therapy. The therapeutic agent delivered by this process attacks only the cells lining the interior of the bladder and has no effect on cells deeper in the bladder lining. For this reason, intravesical therapy is not used if a cancer has progressed beyond stage I. Later-stage cancers are generally treated with intravenous chemotherapeutic agents, which travel throughout the body. Chemotherapeutic regimens vary; some involve the use of a single drug, and others combine two or more drugs. Drugs commonly used to treat bladder cancer include the following:
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 introduces a solution of genetically modified tuberculosis bacteria (Bacillus 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 a new type treatment that is still being tested 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. As of 2014, the Food and Drug Administration had approved three drugs for use with photodynamic therapy—aminolevulinic acid (ALA, or Levulan), methyl ester of ALA (Metvixia cream), and porfimer sodium (Photofrin).
The chance of recovery depends on the stage of the bladder cancer. As with 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.
Bladder reconstruction may be an option for patients who have had a cystectomy. The procedure involves the construction of an artificial bladder out of a section of the small bowel as a reservoir for the collection of urine, as is the case for the natural bladder. Tubes connect the kidney to the artificial bladder, which in turn is connected to the urethra. The flow of urine through the artificial bladder is, therefore, very similar to the natural elimination of urine through the original bladder. In some cases, a person may need to empty the artificial bladder by means of a catheter once or twice a day. Not all patients who have had a cystectomy are candidates for the construction of an artificial bladder.
Preventing bladder cancer focuses on reducing risk. Some of the known risk factors include the following:
exposure to cancer-causing chemicals or substances
consuming a diet with a large amount of 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 lower the risk of developing cancer or to prevent its recurrence. Clinical trials of chemoprevention agents for bladder cancer are also ongoing.
See also Bladder stones; Cancer; Cancer therapy, supportive; Chemotherapy; Oncology; Smoking; Urine culture.
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