While radical cystectomy (RC) remains the standard of care for muscle-invasive bladder cancer (MIBC), it is associated with significant morbidity and long-term quality-of-life impacts. For elderly patients and those ineligible for cisplatin-based chemotherapy, effective bladder-sparing strategies are urgently needed in clinical practice. At a recent major international oncology conference, Dr. Jonathan F. Anker from Mount Sinai presented the latest data from the HCRN GU 20-444 study (Abstract 737). This Phase II clinical trial innovatively explored a pembrolizumab-based, response-guided bladder-sparing strategy in cisplatin-ineligible MIBC patients and conducted an in-depth analysis of the immense potential of circulating tumor DNA (ctDNA) in precisely identifying the population that stands to benefit. Oncology Frontier has summarized the core academic content below.01 Study Background and Design: Exploring a “Response-Guided” Novel Pathway to Spare Radical Resection
For patients with MIBC, transurethral resection of bladder tumor (TURBT) combined with systemic therapy can achieve a pathological complete response (pCR) in a subset of the population. Previous data showed that the pCR rate can reach approximately 40% in patients undergoing radical cystectomy after neoadjuvant pembrolizumab monotherapy. This suggests that a subset of patients highly sensitive to immunotherapy might be spared from radical surgery without an increased risk of recurrence.
HCRN GU 20-444 is an investigator-initiated Phase II clinical trial designed to overcome the bottlenecks of previous bladder-sparing strategies, namely the “lack of effective biomarkers” and “limited treatment options for the cisplatin-ineligible population.” The study enrolled patients with clinical stage T2–T3 MIBC who were ineligible for or declined cisplatin-based chemotherapy (creatinine clearance ≥ 30 mL/min).
The treatment strategy follows a “response-guided” decision tree model:
- Induction Phase: After maximal TURBT, patients received 2 cycles of pembrolizumab (400 mg intravenously every 6 weeks), followed by rigorous clinical restaging (including cystoscopy, biopsy, urine cytology, and pelvic MRI).
- Triage Decision:
- If a clinical complete response (cCR) was achieved, patients retained their bladders and continued with 7 cycles of maintenance pembrolizumab.
- If a cCR was not achieved, patients underwent upfront radical cystectomy or concurrent chemoradiation, followed by 7 cycles of adjuvant pembrolizumab.
The co-primary endpoints of the study were the cCR rate and the ability of cCR to predict clinical benefit (defined as the 2-year metastasis-free survival [MFS] rate for patients with cCR).
02 Efficacy and Safety: 43% of Patients Achieved cCR and Successfully Retained Their Bladders
A total of 46 patients were enrolled between July 2022 and December 2024. Notably, this cohort had an advanced age profile, with a median age of 74 years, and 25% of patients were over 80 years old, accurately reflecting the real-world demographics of the cisplatin-ineligible population.
- Core Efficacy Data: All 46 patients completed clinical restaging assessments. The data showed that 43% (20/46) of patients achieved cCR, and all of these patients successfully avoided upfront radical cystectomy. Among the 26 patients who did not achieve cCR, 11 underwent radical surgery, 5 received upfront chemoradiation, and the remainder received other non-protocol therapies. At a median follow-up of 11 months, no metastatic recurrence events were observed in the cCR bladder-sparing cohort. Regarding local control, only 1 patient experienced a clinical stage T1 local recurrence (which was managed with bladder-sparing interventions); another patient underwent a cystoprostatectomy due to newly diagnosed prostate cancer, and the postoperative pathology confirmed that the bladder remained in a complete response state.
- Safety Data: Treatment-emergent adverse events (TEAEs) were generally consistent with the known toxicity profile of pembrolizumab. Two Grade 5 adverse events were recorded: one cardiac arrest (deemed unrelated to treatment by the investigator) and one fungal pneumonia (which occurred in a patient receiving systemic steroids for immune-related hepatitis).
03 In-Depth Biomarker Exploration: ctDNA Whole-Genome Sequencing Provides Precise Prediction
A major highlight of this study was the use of an ultrasensitive, whole-genome sequencing (WGS)-based approach to generate patient-specific genomic signatures for the evaluation of minimal residual disease (MRD). Compared to traditional deep targeted sequencing, this method prioritizes the breadth of sequencing over depth, effectively overcoming the detection limitations commonly seen in low tumor-volume settings.
Deep Correlation Between ctDNA Dynamics and Efficacy:
- Baseline Status: ctDNA was detectable in approximately 30% of patients at baseline. Data indicated that patients with detectable baseline ctDNA had a significantly lower probability of subsequently achieving a cCR.
- Early Dynamic Clearance (Crucial Finding): All patients who ultimately achieved cCR had an undetectable ctDNA status at the Cycle 2 Day 1 (C2D1) assessment (i.e., after only a single dose of pembrolizumab). This even included 2 patients who had detectable ctDNA at baseline but achieved “clearance” by C2D1. Conversely, the rate of detectable ctDNA remained similar between baseline and C2D1 in the cohort that did not achieve a cCR.
- Survival Benefit Prediction: Comparing patients with undetectable versus detectable baseline ctDNA, the baseline undetectable group demonstrated a significant advantage in metastasis-free survival (HR=11.2). To date, no metastatic recurrences have occurred in the baseline ctDNA-undetectable population.
04 Conclusion and Future Perspectives: The Future Landscape of MIBC Bladder-Sparing Strategies
In summary, Dr. Jonathan F. Anker pointed out that for cisplatin-ineligible MIBC patients, TURBT sequentially followed by pembrolizumab monotherapy, combined with strict and uniform clinical restaging, can achieve a high cCR rate of 43% and safely and effectively guide bladder-sparing decisions.
Simultaneously, ctDNA analysis utilizing ultrasensitive WGS technology has demonstrated immense potential for clinical application. The precise identification of patients with an extremely low risk of recurrence not only provides molecular confidence for “safe bladder-sparing,” but its early dynamic changes (such as clearance after a single treatment cycle) may also serve as pivotal decision points for clinical interventions and regimen adjustments in the future.
Looking ahead, long-term follow-up of the HCRN GU 20-444 study is ongoing. Furthermore, building on this strategic framework, the research group plans to initiate explorations for Cohort 2 (nivolumab plus ipilimumab) and Cohort 3 (enfortumab vedotin plus pembrolizumab), which are expected to further elevate the ceiling for complete response rates in MIBC bladder-sparing treatments.
