A vaccine for tuberculosis is now being used to treat early, potentially aggressive cancers of the lining of the bladder. These superficial, or shallow, cancers can progress to invasive forms that burrow into the bladder muscle and then spread to other parts of the body, becoming incurable.
"The standard approach to one of the more aggressive types of superficial bladder cancer, carcinoma in situ (CIS), has been to surgically remove the bladder if the cancer cannot be eradicated quickly by more conservative means," said Dr. John A. Provet, a urologist at New York University Medical Center.
Previous medications instilled directly into the bladder for this type of cancer, also referred to as transitional cell carcinoma, have had limited success rates. The new treatment using bacille Calmette-Guerin (BCG) may eradicate CIS in 60% of the cases.
BCG was first created in 1906 as a vaccine against human tuberculosis. It is a laboratory-weakened strain of a bacterium that causes TB in cows.
BCG solution is instilled directly into the bladder through a catheter, or soft tube. The treatment is generally performed in a urologist's office. The normal course of therapy is one infusion a week for a period of six to 12 weeks. The body's immune system reacts by attacking the foreign micro-organisms that have entered the bladder.
"Because the bacteria are weakened, they are not capable, except in unusual circumstances, of causing an actual generalized TB infection," explained Provet. "However, they do activate a localized immune response, resulting in inflammation of the bladder."
In unusual cases, the process can spread beyond the bladder to become a full-fledged active infection. When this occurs, it can usually be treated successfully, but the patient must take anti-tuberculosis medication for months.
"The potential benefits of BCG therapy in eradicating the tumor must be carefully weighed against the relative risk of developing tuberculosis-like infection. The medication should not be given to patients until some time after active bleeding within the urinary tract has stopped," Provet emphasized.
BCG has been approved by the U.S. Food and Drug Administration for treatment of CIS. It is also being investigated clinically at NYU and other academic medical centers to treat or prevent recurrences of other types of transitional cell carcinoma of the bladder.
If bladder cancer is going to recur, it usually does so within a year. If patients remain disease-free for four years or more, as many of the patients treated with BCG have, the majority are cured of their disease, Provet said.
"In the past, it was often necessary to sacrifice the bladder to save a life," concluded Provet. "Now with BCG, it should be increasingly possible to save the bladder."