Prior to the advent of BCG immunotherapy, bladder carcinoma in situ often 
progressed to muscle invasion. Intravesical chemotherapy completely eradicates 
the disease in 50% of patients, but fewer than 20% remain disease free after 5 
years. Complete responses have been reported in 70% or more of BCG treated 
patients, nearly two-thirds of which are durable. Controversy over the optimal 
induction and maintenance regimens for BCG immunotherapy remain, but SWOG 
investigators have demonstrated that complete response rates can be increased 
from the expected 73% to 87% with just three additional BCG instillations given 
at 3 months. In complete responders, maintenance BCG using three weekly 
treatments at 6-month intervals improves long-term complete response rates from 
65% to nearly 90%. Caution must be exercised to avoid serious side effects.