Qualitative Interferon-γ Release Assay for Predicting Response to BCG Instillations in Bladder Cancer

This study aims to investigate the potential use of qualitative interferon-γ release assay, specifically T-spot testing focusing on culture filtrate protein 10 (CFP-10) positivity, in predicting the response of patients with high-risk non-muscle invasive bladder cancer (NMIBC) to intracavitary Bacillus Calmette-Guerin (BCG) vaccine instillation.

Patients diagnosed with high-risk NMIBC were retrospectively identified from an institutional database and subsequently underwent prospective T-spot testing. Following the completion of an adequate course of BCG instillation, patients who were unresponsive to BCG were assigned to the study group. By contrast, those who remained recurrence free for at least one year post-treatment were assigned to the control group.

In this cohort of 42 patients with high-risk NMIBC, the median age was 67, and 40.0% were unresponsive to BCG. The distribution comprised 50.0% pTa and 81% high-grade cases. Over a median follow-up of 18 months, the positive BCG response varied between pTa (81%) and pT1 (38%; p = 0.005), and T-spot testing revealed positivity in 75.0% of the control group and 92% in BCG-unresponsive patients (p = 0.235). Notably, CFP-10 positivity was significantly more prevalent in the BCG-unresponsive group, observed in 91.7% of the patients, in contrast to 35.7% in the control group (p = 0.004).

T-spot test or more specifically CFP-10 positivity is a potential marker for predicting response to BCG instillation in patients with NMIBC.