Single immediate instillation of chemotherapy is associated with decreased recurrence and progression in patients with high-risk non-muscle-invasive bladder cancer who receive adjuvant induction bacillus Calmette-Guérin therapy.

Objectives: To investigate whether a single intravesical instillation of chemotherapy is associated with improved oncological outcomes in patients with high-risk non-muscle-invasive bladder cancer who receive adjuvant induction bacillus Calmette-Guérin therapy.

Methods: This multi-institutional retrospective study included 205 patients with high-risk non-muscle-invasive bladder cancer who received adjuvant induction bacillus Calmette-Guérin therapy. Patients were divided into two groups: those who received the combined therapy of a single instillation of chemotherapy plus subsequent adjuvant induction bacillus Calmette-Guérin therapy (combined therapy group), and those who received adjuvant induction bacillus Calmette-Guérin therapy alone (bacillus Calmette-Guérin monotherapy group). Multivariable analyses using the inverse probability of treatment weighting method and Fine-Gray competing risk regression models were performed to evaluate the impact of a single instillation of chemotherapy on intravesical recurrence-free survival and muscle-invasive bladder cancer-free survival.

Results: Among the 205 patients, 130 (63%) and 75 (37%) were classified as the combined therapy and bacillus Calmette-Guérin monotherapy groups, respectively. Multivariable analyses using the inverse probability of treatment weighting method showed that a single instillation of chemotherapy was significantly associated with longer intravesical recurrence-free survival (hazard ratio 0.279; P < 0.001) and muscle-invasive bladder cancer-free survival (hazard ratio 0.078; P < 0.001). Fine-Gray competing risk regression model revealed that a single instillation of chemotherapy was associated with a significantly lower probability of intravesical recurrence and muscle-invasive bladder cancer progression, with an adjusted subdistribution hazard ratio of 0.477 (P = 0.008) and 0.261 (P = 0.043), respectively.

Conclusion: A single intravesical instillation of chemotherapy may be a potential treatment option in patients with high-risk non-muscle-invasive bladder cancer who receive adjuvant induction bacillus Calmette-Guérin therapy.