What is the cancer of the bladder?
The bladder is a muscular bag situated in the mid-line of the pelvis at the lowest point in the abdomen, immediately behind the pubic bone. There are three principal layers in the bladder wall. The inside mucous membrane (mucosa), the muscle layer of circular and longitudinal fibers, and the outer layer, the peritoneum.
Primary bladder cancer constitutes about seven per cent of cancers in men and about three per cent of new cancers in women. It is three times as common in men as in women.It is more common in white people than in black people and the average age at diagnosis is 65.
At the time of diagnosis about 85 per cent of bladder cancers are still limited to the bladder only. The remainder have spread to the lymph nodes (glands).
Stages of a bladder cancer
Bladder cancer always starts in the mucosa. In the earliest stages it is confined to this layer and is called carcinoma in situ. For a time the cancer grows only towards the interior of the bladder. At this stage, if detected, it can be cured by simple local treatment without opening the bladder.
The next stage is for the cancer to spread outwards, deeper into the muscular layer of the bladder. At the same time the cancer will become larger on the interior surface and will spread sideways.
The advancing cancer will next grow right through the wall of the bladder to invade the peritoneum or the other tissues on the outside of the bladder. While the cancer is confined to the mucosa, spread to distant lymph nodes or further is unlikely.
But by the time the muscle of the bladder wall is invaded, about 13 per cent of cancers will also have spread to lymph nodes.
Once the cancer has penetrated the wall and is in the surrounding tissue, in almost 90 per cent of cases it has also spread to the lymph nodes.
Symptoms of bladder cancer
Bladder cancer shows itself by the painless passage of blood in the urine (haematuria), by the frequent need to urinate or by pus in the urine and a burning pain on urination. These signs are commonly an indication of other less serious conditions, but they should always be taken seriously, especially when occurring for the first time in older people.
They always require proper investigation. Sometimes pain is caused by the retention of blood clots in the bladder from bleeding from the tumor.
Pain may also result from spread of the cancer to local nerves.
People with advanced bladder cancer may have symptoms caused by the local and the more distant spread of tumor. There may be pain in the lower back, obstruction of the ureters (the tubes that carry urine down to the bladder from the kidneys), or bone pain from secondary cancer. Rarely, there may be a mass that can be felt in the area of the bladder.
Causes of bladder cancer
The causes of most bladder cancers remain uncertain, but some causes are known.
- The products of tobacco tars acquired by cigarette smoking and excreted in the urine
- Certain chemicals such as aniline dyes, beta-naphthylamine and benzidine
- Some chemicals encountered in rubber manufacture
- Drugs such as phenacetin and cyclophosphamide
- Long-term bladder inflammation
- The African parasitic disease schistosomiasis
- The presence of bladder stones
The changes in the bladder lining that lead to cancer occur gradually and progressively. The most important of the known causal factors are the substances alpha and beta naphthylamine, which are excreted into the urine of cigarette smokers.
Heavy cigarette smoking is believed to be the cause in half the cases in men and a third of the cases in women.
Exposure to occupational chemicals, especially in the rubber, petroleum, leather and dye industries, probably cause about 30 per cent of cases in men. Artificial sweeteners were at one time suspected of causing bladder cancer, but several research projects have failed to confirm any causal link.
In almost all bladder cancers, the cancer cells show a loss of part of the long arm of chromosome number 9. Many bladder cancers also show loss of the short arms of chromosomes 11 and 17.
The supposition is that the cancer may be caused by loss of suppressor genes on these chromosomes.
How to diagnose bladder cancer?
The urine can be examined for the presence of cancer cells.
X-rays taken after injection of a radio-opaque dye may show a mass in the bladder. The diagnosis can be confirmed by looking directly at the inside of the bladder through a viewing tube called a cystoscope.
Another method of confirmation uses CT scanning or ultrasound scanning. The use of the cystoscope allows a sample of tissue (biopsy) to be taken for examination and a positive diagnosis.
Bladder cancer treatment
In about half of those people presenting with signs of bladder cancer, the tumor is still in the early stages and is confined to the inner lining of the bladder and can readily treated.
Such early cancers can be destroyed by laser beam or by snipping off the tumor and burning with a hot wire (cautery) passed through a cystoscope. This procedure is known as a transuretral resection of a bladder tumor (TURBT) Some cases are treated by inserting anticancer drugs directly into the bladder.
Anti-cancer drugs may be put directly into the bladder to try to prevent the cancer from recurring.
If the cancer is first discovered at a stage when it has already spread deeply into the wall of the bladder, locally in the lower abdomen or widely throughout the body, major surgery and/or radiotherapy will be necessary. The whole bladder may have to be removed.
Radiotherapy may be used to treat invasive bladder cancer to try and avoid having to remove the bladder.
Surgical removal of the bladder is called cystectomy. After cystectomy, the ureters, which constantly bring urine down from the kidneys, have to be connected elsewhere.
They may be implanted into the colon so that the urine passes out with the feces, or they may be implanted into an artificial bladder made from an isolated segment of bowel which drains out through the skin. Such transplantation is called urinary diversion.