Introduction

Though BCG immunotherapy reduces the incidence of recurrence and progression there are still patients who fail therapy. This could be due to an inability to generate activated antigen specific T cells. CLTA4 modulates the activation of T cells. The objective of this study was to determine if CTLA4 (Rs733618, Rs4553808, Rs5742909, Rs231775, Rs3087243, Rs565213 and Rs960792) Single Nucleotide Polymorphisms (SNPs) modulate the incidence and outcomes to BCG immunotherapy.

Methods

DNA was obtained from bladder cancer patients attending the National University Hospital (n=139) and healthy controls (n=150) (IRB approval, NHG DSRB: 2012/00475). SNPs were evaluated using PCR followed by high resolution melt analysis. Patients received either standard or low dose BCG or low dose BCG+IFNα. The median length of follow up was 97 months (range 2.4 - 205.2 months). Time to events are presented as mean±standard error (95% confidence intervals) in months. Multivariate Cox & Logistic regressions were performed to assess the impact of the genotypes, treatment, tumor stage, grade, age, smoking history and gender on time to clinical outcomes (recurrence, progression and death) and their incidences, respectively. Analysis was performed using SPSS 23.0 and p<0.05 was taken to be significant.

Results

There was no statistical difference between the 3 treatment groups, therefore standard BCG and low BCG (B) were combined and compared to low dose BCG+IFNα (BI). BI therapy significantly improved outcomes for patients with Rs733618CC (B vs BI, 13 patients, p=0.019), Rs7565213GG (B vs BI, 52 patients, p=0.015) and Rs960792TT (B vs BI, 52 patients, p=0.04) in terms of time to recurrence and with Rs231775GG (B vs BI, 41 patients, p=0.039) and Rs7565213GG (B vs BI, 53 patients, p=0.032) in terms of time to progression. Patients with Rs960792CC had earlier recurrences with BI therapy (B:10 vs BI:11 patients, p=0.08). In subjects with the combination of genotypes: Rs3087243GG, Rs7565213GG and Rs960792TT (B:22 vs BI:18 patients), treatment with BI resulted in increased recurrence free survival time (97.51±20.44 (57.45 - 137.57) months vs 154.64±16.94 (121.45 - 187.83) months, p=0.025) and increased time to cancer specific death (75.13±14.31 (47.07 - 103.18) months vs 150.00±19.09 (112.58 - 187.42) months, p=0.047).

Conclusions

IFNα modulates response to BCG positively in subjects with CTLA4 genotypes Rs3087243GG, Rs7565213GG and Rs960792TT.

Funding

NCIS/NMRC