There is a lack of long term data on the implication of anemia on non-muscle invasive bladder cancer (NMIBC), especially those on intravesical Bacillus Calmette-Guérin (BCG) immunotherapy.

NMIBC patients receiving BCG therapy from 2001 to 2020 were identified in a territory-wide database in Hong Kong. Patients were dichotomised into two groups according to the status of anemia at BCG treatment initiation. Men with a hemoglobin level of <13.0 g/dL or women <12.0 g/dL were classified to the anemia group. The outcomes of interest were overall survival (OS), cancer-specific survival (CSS), recurrence-free survival (RFS), and progression-free survival (PFS) calculated with Kaplan-Meier plot. Multivariable Cox regression analysis was adopted to adjust for confounders. Estimated hazard ratio (HRs) and 95% confidence intervals (CIs) were presented.

From a median follow-up of 11 years, of 2302 patients with NMIBC treated with intravesical BCG, 940 patients (40.8%) were classified to the anemia group while 1362 (59.2%) belonged to the control group. OS (P<0.001), CSS (P=0.011) and RFS (P=0.043) were inferior in the anemia group while PFS (P=0.832) showed no difference. Multivariable Cox regression analysis identified that anemia was an independent predictor of OS (HR 1.40, 95% CI 1.23-1.60, P<0.001).

Anemia at treatment initiation was an independent risk factor for survival in intermediate-high risk NMIBC patients receiving BCG. Physicians should be aware of its implications at early phases of treatment.