Approximately 60,000 new cases of bladder cancer are diagnosed in the United States each year, and this disease accounts for around 13,000 deaths annually.
Bladder cancer is more common in men, who are three times more likely to acquire the disease than women. This may be due to more frequent exposures to known carcinogens among men.
Bladder cancer is also more common among whites than blacks. It is unclear whether this is due to genetic differences or to dissimilarities in exposure to aggravating agents.
What is Bladder Cancer?
More than 90% of bladder cancers arise from the transitional epithelium that lines the bladder. Transitional epithelium is a specialized, layered epithelium whose spherical surface cells flatten and stretch as the bladder fills; when the bladder empties, the cells once again assume their spherical shape.
Because epithelial cells typically undergo relatively rapid growth and division, they are susceptible to stimuli that damage their genetic material. Furthermore, because the bladder temporarily stores a fluid that contains byproducts of metabolism, the transitional cells are subjected to high concentrations of potentially toxic agents.
Most transitional cell carcinomas are papillary (fingerlike), superficial, and well-differentiated; they respond reasonably well to treatment, but more than 40% of patients experience recurrence at the same or another site in the bladder.
Sessile (flat) tumors tend to be more invasive; they are more likely to metastasize early and are therefore more difficult to treat.
Other types of bladder cancer include squamous cell carcinomas, which are more common in people with chronic mucosal irritation (e.g., bladder stones), and adenocarcinomas, which often spread to the bladder from the colon or other intestinal sites.
Owing to the venous anatomy of the pelvis, bladder cancer tends to spread initially to local lymph nodes, and then to the liver, lungs, and bone.
Signs and Symptoms of Bladder Cancer
Most patients with bladder cancer first present with unexplained hematuria (blood in the urine). This may be visible to the naked eye, or it may be discovered incidentally when the urine is being examined for other reasons (e.g., occupational screening, annual physical examination, etc.).
Other signs and symptoms include:
- Urinary burning
- Urinary frequency
- Bladder pain with voiding
- Pelvic pain (usually in advanced cancer)
- Anemia (often discovered incidentally when bloodwork is ordered for other reasons, but symptoms of anemia – fatigue, poor exercise tolerance, lightheadedness, rapid heart rate – may prompt a person to seek medical advice)
Risk Factors for Bladder Cancer
Smoking is the primary risk factor for bladder cancer, causing more than half of cases. (Bladder Cancer in The Merck Manual, 18th Edition. 2006:2047-49)
Although the connection between bladder cancer and smoking may seem spurious to the uninformed, it helps to remember that the lungs absorb a bounty of toxins from cigarette smoking, and these agents must somehow be eliminated from the body. The bladder is the terminal resting point for chemicals acquired from cigarette smoking.
Other risk factors for bladder cancer include:
- Exposure to hydrocarbons and other chemicals found in the processing of leather and the manufacture of rubber and tires
- Exposure to aniline dyes and other aromatic amines (dye industry)
- Chronic bladder irritation (bladder stones, some parasitic infestations)
- Heavy phenacetin use (a carcinogenic [and now-outlawed] pain reliever that is sometimes used to cut cocaine)
- High-doses of cyclophosphamide (a drug used to treat lymphomas and other cancers)
- Use of aristolochic acid (found in some herbal weight-loss preparations)
(Adapted from Cohen R, Brown R. Microscopic hematuria. N Engl J Med 2003;348:2330-8)
Diagnosis and Treatment of Bladder Cancer
Once hematuria is discovered or a patient presents with complaints that raise the suspicion for bladder cancer, the evaluation is relatively straightforward:
- Intravenous urography (ultrasound or CT may be used if the patient is pregnant or allergic to intravenous contrast) outlines the urinary tract and reveals abnormalities.
- Cystoscopy (the use of a scope passed through the urethra) affords direct visualization of the bladder interior. Any abnormal areas are biopsied.
- Abdominal or pelvic CT and chest x-ray are used to determine whether a tumor has spread beyond the bladder.
Treatment Considerations
- Superficial bladder cancers rarely cause the death of a patient, although they may recur. Early tumors are usually removed or fulgurated (i.e., cauterized) via cystoscopy.
- Repeated applications of chemotherapeutic drugs or BCG – a solution that stimulates the immune system to kill cancer cells – may be used to reduce the risk of recurrence.
- Invasive tumors may require partial or complete removal of the bladder; a procedure to divert urine from the kidneys to a “neobladder” is also usually performed.
- Systemic chemotherapy is useful for patients with widely metastatic disease, but the prognosis is poor. Poorer outcomes are also associated with progressive or recurrent tumors and with squamous cell carcinomas.
Bladder cancers are relatively common; most can be prevented through smoking cessation and by minimizing occupational or recreational exposures to known carcinogens.
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