90% of all bladder cancers are transitional cell carcinomas.
Predisposing Causes and Prevention
- Cigarettes. Cigarette smoking is involved in 50% of cases in men and 30% of cases in women.
- Dyes. Workers in the dye, petroleum, chemical, printing, rubber and leather industries appear to be at increased risk.
- Chemotherapy agents such as cyclophosphamide increase the risk of bladder cancer development. There is also an increased risk in patients who have undergone pelvic and abdominal radiation therapy.
- Others. Chronic infection and calculi may increase the risk of malignancy.
Transurethral resection is the initial form of treatment for all bladder cancers. If the tumor is diagnosed as being superficial, without invasion into the deeper layers of the bladder wall, then only periodic cystoscopic evaluation is necessary to identify tumor recurrences.
If there is associated carcinoma in situ or if tumor recurrences become more frequent, adjunctive intravesical chemotherapy is employed. This may be in the form of immunoagents or chemotherapeutic agents. These are instilled directly into the bladder via a catheter. Most of these agents are administered in the office weekly for 6-8 weeks with subsequent follow up check cystoscopies. The use of monthly maintenance intravesical chemotherapy or immunotherapy is controversial.
A. Immunoagents. Bacille Calmette-Guerin (BCG). This is an attenuated strain of tuberculosis. The exact mechanism by which BCG exerts its antitumor effect is unknown. BCG is effective therapeutically and prophylactically with complete responses reported in 30-75% of patients with residual carcinoma in situ with one or two years of therapy. Recurrence rates are significantly reduced, and the time for progression is significantly increased.
B. Chemotherapeutic agents. In certain circumstances, Mitomycin C, Thiotepa and Doxorubicin may also be useful as agents for intravesical chemotherapy.
C. Laser vaporization has the distinct disadvantage that tumor samples are not available for pathologic examination unless taken separately before laser vaporization. The vaporization may have the advantages of being done under sedation alone, particularly for small recurrences, and possibly being less likely to promote tumor dissemination within the bladder.
Patients with tumors that are not superficial and invade the deeper layers of the bladder, situated in the dome or posterior bladder wall, or have their tumors in a diverticulum may be candidates for a partial cystectomy. Random biopsies of the bladder to exclude carcinoma in situ should be performed to rule out this associated problem if a partial cystectomy is being entertained.
This is the standard method of treatment for those with muscle-invasive disease, and in women includes removal of the uterus and anterior vaginal vault. In men, the urethra should be removed if biopsies have shown cancer at the level of the bladder neck or prostatic urethra.
Studies are underway to see if a combination of transurethral resection, follow up, systemic chemotherapy with or without external beam radiation and/or intravesical chemotherapy may allow the patient to keep the bladder and have the same prognosis.
External beam radiation may be an alternative to radical cystectomy in patients with muscle-invasive bladder cancer; however, local recurrence is common.
About 1/3 of patients who present with invasive bladder cancer are found to have regional or distant spread. The use of neo-adjuvant chemotherapy prior to surgery may improve survival in this group of patients; use of adjuvant chemotherapy with agents presently available has not been proven to result in high cure rates.
About 1/3 of patients with invasive disease develop distant metastases despite treatment such as a radical cystectomy.