Diminished Short-Term Efficacy of Reduced-Dose Induction BCG in the Treatment of Non-Muscle Invasive Bladder Cancer

SIMPLE SUMMARY: Intravesical Bacillus Calmette-Guérin (BCG) instillation is an important treatment for non-muscle invasive bladder cancer. Recent BCG shortages have forced urologists to try alternative intravesical BCG regimens to maximize a limited supply. The goal of our study was to compare the efficacy of reduced-dose induction BCG versus full-dose induction BCG in regards to bladder tumor recurrence rate. We hypothesized that patients receiving reduced-dose induction BCG would have a higher recurrence rate. In our single-center retrospective cohort of 139 patients meeting the inclusion criteria, 38.6% of patients who received reduced-dose induction BCG developed a recurrence within one year compared to 33.7% of propensity-matched patients who received full-dose induction BCG. We concluded that reduced-dose induction BCG was associated with a significantly greater risk of recurrence within one year than full-dose induction BCG therapy. These data suggested that reduced-dose induction BCG may not be equivalent or non-inferior to full-dose administration in the short term. ABSTRACT: The ongoing Bacillus Calmette-Guérin (BCG) shortage has created challenges for the treatment of non-muscle invasive bladder cancer (NMIBCa). Our objective was to evaluate the efficacy of reduced-dose induction BCG (RD-iBCG) compared to full-dose induction BCG (FD-iBCG) regarding recurrence rates. We hypothesized that patients receiving RD-iBCG may recur at a higher rate compared to those who received FD-iBCG therapy. A retrospective review of all patients with NMIBCa treated with intravesical therapy at our institution between 2015–2020 was conducted. Inclusion criteria consisted of having a diagnosis of AUA intermediate or high-risk NMIBCa with an indication for a six-week induction course of FD or RD-BCG with at least 1 year of documented follow up. The data were censored at one year. Propensity score matching for age, sex, tumor pathology, and initial vs. recurrent disease was performed. The primary endpoint was bladder cancer recurrence, reported as recurrence-free survival. A total of 254 patients were reviewed for this study. Our final cohort was 139 patients after exclusion. Thirty-nine percent of patients had HGT1 disease. 38.6% of patients receiving RD-BCG developed a recurrence of bladder cancer within a one-year follow-up as compared to 33.7% of patients receiving FD therapy. After propensity matching, this value remained statistically significant (p = 0.03). In conclusion, RD-iBCG for NMIBCa is associated with a significantly greater risk of recurrence than full-dose induction therapy, suggesting that RD-iBCG may not be equivalent or non-inferior to full-dose administration in the short term.