AUA 2018: Switching of Bacillus Calmette-Guerin Strain at Second BCG Therapy May Reduce BCG-Related Side Effects in Patients with BCG-Relapsing Tumors

San Francisco, CA ( Currently, two strains of Bacillus Calmette-Guerin (BCG) (Tokyo-172 and Connaught) are used for the treatment of patients with high-risk non-muscle invasive bladder cancer. Recent studies have proposed that BCG resistance may be related to the type of strain used. Some have advocated that resistance may be secondary to clonal selection from the specific strain used, arguing that treatment with a different strain may rescue patients who have had an initial response to BCG (BCG relapsing). Dr. Niwa, from Keio University in Tokyo Japan, presents a retrospectives study which evaluates the clinical efficacy and safety of switching of BCG strain at the second BCG therapy in patients with BCG-relapsing non-muscle-invasive bladder tumor, defined as recurrence after achieving a disease-free status for 6 months.

The study performed a retrospective review of 97 patients treated with a second BCG induction for BCG-relapsing tumor. Of these patients, 71 (73.2%) and 26 (26.8%) underwent initial BCG treatment d with the Tokyo-172 strain and Connaught strain, respectively. At second BCG induction, 28 (28.9%) patients were given a different BCG strain (switching group), and 69 (71.1%) patients were given the same BCG strain (non-switching group). The study defined four distinct groups: Tokyo-172 to Tokyo-172 strain, Connaught to Connaught strain, Tokyo-172 to Connaught strain, and Connaught to Tokyo-172 strain. The 5-year recurrence-free survival (RFS) rates for the above groups were 52.9±7.7%, 63.5±14.8%, 85.7±9.4%, 41.0±14.7%, respectively. here was no significant difference in RFS between the switching and non-switching groups (64.7±9.6% vs. 54.8±6.9%, p=0.427). There was also no significant difference in the progression-free survival rate between the switching and non-switching groups (95.4±2.6% vs. 96.0±3.9%, p=0.674). Side effects were significantly lower in the switching-group compared to the non-switching group (32% vs. 63%, p<0.05). 

In summary, switching of BGC strains did not have a significant effect on RFS on patients with BCG-relapsing disease treated with a second BCG induction. BCG related side effects appear significantly lower in patients in whom the BCG strain was changed at second induction. The study has several limitations mainly the low numbers used in the analysis. Given bladder cancer heterogeneity the study will need a significantly higher number of patients to note a difference. Moreover, the presenter acknowledges that significant strain cross-over could have occurred during maintenance regimens which confounds the results presented. 

Presenter: Naoya Niwa, MD (Keio University, Tokyo Japan)

Written by: Andres F. Correa, MD, Urologic Oncology Fellow, Fox Chase Cancer Center, Philadelphia, PA at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA

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