Efficacy of Mycobacterium Phlei Cell Wall-Nucleic Acid Complex (MCNA) in BCG-Unresponsive Patients

Background: We have previously reported the results of a prospective multi-institutional study on the efficacy of MCNA in patients who recurred after intravesical BCG treatment [1]. Since that publication, a new standardized definition for BCG-unresponsiveness has been established [2]. Objective: We re-analyzed the oncologic outcomes following intravesical MCNA in patients classified as BCG-unresponsive according to the new definition. Methods: For this analysis, we focused on the enrolled patients who satisfied the requirements for BCG Unresponsiveness: i.e. adequate BCG treatment (at least 5/6 induction and 2/3 maintenance instillations) and high grade tumor within 6 months of prior BCG. Treatment course included 6 weekly intravesical instillations of 8 mg MCNA followed by 3 weekly instillations at months 3, 6, 12, 18, and 24. Followup assessments included cystoscopy, urine cytology and biopsy. Patients absent of high grade disease confirmed by central review of biopsy were deemed disease-free. Results: Of the 129 patients enrolled, 94 (68 CIS with/without papillary tumors, 26 papillary only tumors) fit the criteria for the new BCG Unresponsive definition. Overall, disease free survival (DFS) for all BCG unresponsive patients was 48.9% (95% CI 38.0-59.0%) at 6 months, 34.8% (95% CI 24.7-45%) at 1 year and 28.3% (15.7-34.3%) at 2 years post induction. In the group with papillary tumors, DFS measured at months 6, 12, and 24 were: 61.2% (38.2-77.8%), 61.2(38.2-77.8%), and 50.1% (27.5-69%). In the CIS-containing group, the corresponding DFS were: 44.8% (32.3-56.4%), 26.5% (16.3-37.9%), and 16.6% (8.6-26.9%), respectively. Conclusions: For patients who are BCG Unresponsive, MCNA has the potential to render 26.5% of patients with CIS and 61.2% of patients with papillary tumors disease-free for at least 1 year with an intact bladder. The higher efficacy noted in the true BCG-unresponsive cohort than was previously reported with all-comers emphasizes the importance of having clearly defined criteria for clinical trials investigating new intravesical therapies after BCG failure.