Robert Svatek, MD, highlights SWOG S1602 trial in BCG-naïve NMIBC

In the following interview, conducted at the 2026 ASCO Genitourinary Cancers Symposium in San Francisco, California, Robert S. Svatek, MD, discussed the scientific rationale behind the SWOG S1602 trial (NCT03091660), evaluating BCG strain differences and intradermal BCG before intravesical therapy for patients with BCG-naïve non–muscle invasive bladder cancer (NMIBC).¹ Svatek is a professor and the Gary and Glenda Woods President’s Distinguished University Chair in GU Oncology at UT Health San Antonio in Texas.

Svatek began the discussion by highlighting the historical context for the study. He explained that the original BCG strain was developed at the Pasteur Institute in France in the early 1900s and subsequently distributed worldwide, where serial passaging in different laboratories led to the development of genetically distinct daughter strains. In the United States, only the TICE strain is FDA approved and widely used, a situation that has contributed to treatment disruptions during BCG shortages. Because laboratory data suggest immunologic differences among strains, the trial was designed to determine whether these differences translate into clinically meaningful outcomes and to assess whether an alternative strain could help mitigate supply challenges without compromising efficacy.

The study ultimately evolved into a 3-arm, randomized controlled trial conducted in collaboration with SWOG and international partners. Although an initial plan to run parallel European and US components did not materialize, the trial was preserved through collaboration with investigators in Tokyo, who provided access to the Japanese Tokyo strain of BCG. This allowed investigators to compare TICE BCG, Tokyo BCG, and Tokyo BCG with an intradermal priming strategy. The priming approach—based on more recent work from the Pasteur Institute—was designed to enhance immune activation by administering an intradermal BCG vaccine prior to standard intravesical therapy, with the goal of recruiting more T cells to the bladder. The primary endpoint was high-grade recurrence-free survival (HR-RFS).

The key findings presented at the meeting showed that the Tokyo strain was noninferior to TICE BCG in regard to the primary end point in the overall study population (HR, 0.82; 95.8% CI, 0.63 to 1.08). The Tokyo strain was also non-inferior to TICE in treating carcinoma in situ (6-month CR, 66.4% vs 70.2%), supporting its potential role as an alternative strain in the US. However, the intradermal priming strategy did not demonstrate superiority over standard intravesical BCG in regard to HG-RFS (HR, 1.0; 95.8% CI, 0.76 to 1.33).

Together, these results suggest that while strain substitution may be a viable strategy to address ongoing supply constraints, the addition of priming does not appear to improve clinical outcomes.

Editor’s Note: Svatek reports relevant disclosures with Japanese BCG laboratories, Merck, CG Oncology, Rapamycin Holdings, Emtora, and Biodexa.

REFERENCE

1. Svatek RS, Tangen C, Meeks JJ, et al. SWOG 1602: A phase III randomized trial to evaluate BCG strain differences and priming with intradermal BCG before intravesical therapy for BCG-naïve high-grade non-muscle invasive bladder cancer (NCT #03091660). Presented at: 2026 American Society of Clinical Oncology Genitourinary Cancers Symposium. February 26-28, 2026. San Francisco, California. Abstract LBA629. https://meetings.asco.org/meetings/2026-asco-genitourinary-cancers-symposium/334/16917