Callis, Samuel

TPS913 Background: A subset of patients with MIBC who receive neoadjuvant therapy (NAT) prior to radical cystectomy (RC) have a pathologic complete response (pCR) at the time of RC. With pCR rates of 22-42% in patients with MIBC following NAT (+/- ICI), whether a subset of patients with good clinical response to NAT can avoid RC is an important unanswered question, especially with the development of more active systemic therapies. HCRN 16-257 evaluated maintenance nivolumab in lieu of cystectomy in patients with MIBC who experienced clinical complete response (cCR) following neoadjuvant GC and nivolumab. The cCR rate was 48%, but 8/33 (24%) patients who elected bladder preservation subsequently underwent cystectomy for local disease recurrence. The RETAIN trial also evaluated omission of local therapy following neoadjuvant therapy with a 2-year bladder preservation rate in patients with ≤T1 disease following NAC of 54% (22/41). Of the 9/25 (36%) patients on that trial developed metastatic disease, 8/9 developed localized disease before metastasizing. These data illustrate the critical role that local therapy plays in patients with MIBC. For this reason, we believe that radiotherapy to the bladder combined with ICI will improve bladder intact event-free survival (BI-EFS). This trial also allows for patients to opt for bladder preservation based on a good clinical response to NAT. Methods: This is a single arm, phase 2 trial (NCT07061964) evaluating risk-adapted bladder preservation therapy for patients with MIBC following NAT. NAT consists of any NCCN guideline concordant therapy for MIBC. Patients with cT2-T4aN0M0 MIBC who complete NAT will be eligible if they have ≤T1 disease on post-NAT TURBT, confirmed by biopsies of prior tumor sites and systematic sampling (left/right lateral walls, dome, posterior wall, trigone). Patients will receive 55 Gray (Gy) in 20 fractions of radiotherapy (RT) to the bladder with 1 year of pembrolizumab. The primary objective is to evaluate whether 3-year BI-EFS is at least 70% in participants with < = T1 (without multifocal CIS) following NAT and RT with 1 year of pembrolizumab. Secondary objectives include local muscle invasive recurrence-free survival, metastasis-free survival (MFS), overall survival (OS), the rate of salvage cystectomy, and evaluation of the frequency and severity of toxicities in participants who receive RT and pembrolizumab. Plasma and urine will be banked for future correlative studies. S2427 was activated in September 2025 with an accrual goal of 111 patients. Clinical trial information: NCT07061964 .

TPS354 Background: Carriers of germline pathogenic variants or mutations in BRCA2 and BRCA1 (referred to here as gBRCA1/2m) are enriched in metastatic prostate cancer (PrCa), and now have FDA-approved options for PARP inhibitors in late-stage disease. The NCCN guidelines recommends germline genetic testing for PrCa patients with metastatic, node positive and high risk localized prostate cancer. Prior studies have shown that gBRCA1/2m carriers with PrCa are more likely to have high-risk disease (6,7) and to develop lethal disease even after curative intent treatment (8,9). In other gBRCA1/2m-related cancers (breast, ovarian and pancreas), platinum-based regimens are part of neoadjuvant and front-line metastatic therapy options. Carboplatin is a well-tolerated, widely available and inexpensive DNA-damaging alkylating agent that is familiar to oncologists. The study hypothesis is that 4 cycles of neoadjuvant carboplatin, followed by radical prostatectomy for patients with localized high/very high risk PrCa and g BRCA1/2m will result in a meaningful pathologic complete response (pCR) rate. Methods: S2210 is a single-arm, open label study of 12 wks neoadjuvant carboplatin (4 cycles of AUC 5 every 21 days), followed by radical prostatectomy. Key eligibility criteria include people with high/very high-risk disease: cT3a or Grade Group 4-5 PrCa and/or PSA>20 ng/mL, have no evidence of distant metastases by conventional imaging (PSMA-PET-detected mets permitted if conventional imaging is negative and surgeon deems PSMA-detected sites resectable), who are candidates for radical prostatectomy and carboplatin, and have documented evidence of gBRCA1/2m through testing in a CLIA-certified lab. ADT prior to registration is permitted but must be discontinued on study. The study hypothesis is that the study treatment will result in ³30% rate of pathologic complete response (pCR, primary endpoint). A two-stage design will be used such that if ³1 of first 20 eligible patients achieves pCR, 20 further evaluable patients will be enrolled. This design has a significance level of 4.7%, and a power of 99%. Secondary endpoints include biochemical recurrence-free (at 2-, 3-, 5-yrs), metastasis-free and overall survival. Translational/correlative studies include analysis of 2nd allele inactivation in tumor, HRD signature, and ctDNA signature for monitoring of recurrence. S2210 was activated in August 2023. Clinical trial information: NCT05806515 .