Identifying patients most likely to benefit from neoadjuvant immune checkpoint inhibitor (ICI) therapy remains an important challenge in the management of muscle-invasive bladder cancer (MIBC). Although ICIs have demonstrated meaningful clinical activity before radical cystectomy, treatment responses are heterogeneous, and reliable biomarkers are needed to better guide patient selection.
In the study “Tumor Mutational Burden Predicts the Outcome of Patients with Muscle-Invasive Bladder Cancer Undergoing Immune-Checkpoint Inhibitor-Based Neoadjuvant Therapy,” Chiara Mercinelli, Giuseppe Basile, Giovanni L. Pastorino, Antonio Cigliola, Brigida A. Maiorano, Valentina Tateo, Michela Piacentini, Debora Serafin, Gualtiero Guandalini, Roberta Lacava, Gaia Latini, Maurizio Colecchia, Alberto Briganti, Marco Moschini, Francesco Montorsi, Dean Pavlick, Jeffrey S. Ross, and Andrea Necchi investigated whether tumor mutational burden (TMB) could serve as a predictive biomarker for patients receiving neoadjuvant immunotherapy.
Bladder Cancer: Symptoms ,Causes, Stages, Diagnosis and Treatment
What Is Tumor Mutational Burden?
Tumor mutational burden (TMB) is a biomarker that measures the number of somatic mutations present within a tumor genome, typically reported as mutations per megabase (mut/Mb). It has been widely investigated as a potential predictor of response to immune checkpoint inhibitors across several cancer types.
Despite growing interest in TMB, its clinical role in patients with muscle-invasive bladder cancer undergoing neoadjuvant immunotherapy has not been fully established. The authors therefore evaluated whether baseline TMB could predict pathological complete response and long-term clinical outcomes.
Study Design
The investigators performed a pooled analysis of patients enrolled in three prospective clinical trials evaluating neoadjuvant immune checkpoint inhibitor–based therapy:
- PURE-01
- SURE-02
- NURE-Combo
Baseline tumor mutational burden was assessed using tumor tissue obtained from transurethral resection of the bladder tumor (TURBT) before treatment.
The study evaluated the association between TMB and:
- Pathological complete response (CR)
- Event-free survival (EFS)
- Overall survival (OS)
The investigators also assessed different TMB thresholds to identify the level that best predicted treatment response.
Patient Population
The pooled analysis included patients with muscle-invasive bladder cancer treated with neoadjuvant immunotherapy across the three prospective studies. Baseline clinicopathological characteristics and tumor mutational burden were analyzed before treatment, and pathological response was assessed following definitive surgery.
Primary Endpoint: Pathological Complete Response
The primary objective of the study was to determine whether baseline tumor mutational burden could predict pathological complete response following neoadjuvant immune checkpoint inhibitor therapy.
The analysis demonstrated that higher TMB was associated with an increased likelihood of achieving a complete pathological response. The investigators also identified an optimal TMB threshold associated with treatment response, and patients with higher TMB levels showed progressively greater probabilities of complete response. Importantly, the association between higher TMB and pathological response remained significant after multivariable analysis.
The predictive value of TMB was consistent across the different neoadjuvant immunotherapy regimens included in the pooled analysis, suggesting that its clinical relevance was not limited to a specific treatment approach.
Results
- Higher baseline TMB was associated with a greater likelihood of pathological complete response.
- An optimal TMB threshold predictive of complete response was identified.
- Increasing TMB levels were associated with progressively higher probabilities of complete response.
- Higher TMB remained an independent predictor of complete response in multivariable analysis.
- The predictive effect of TMB was consistent across the different neoadjuvant immunotherapy regimens.
Long-Term Clinical Outcomes
In addition to predicting pathological response, the investigators evaluated the relationship between tumor mutational burden and long-term survival outcomes.
Patients with higher TMB experienced more favorable event-free survival and overall survival compared with patients whose tumors had lower mutational burden. These findings suggest that baseline TMB may identify a subgroup of patients who derive particularly durable benefit from neoadjuvant immune checkpoint inhibitor therapy.
Results
- Higher TMB was associated with improved event-free survival.
- Higher TMB was associated with improved overall survival.
- Patients with the highest TMB demonstrated the most favorable long-term outcomes.
Clinical Perspective
This pooled analysis supports tumor mutational burden as a clinically informative biomarker in patients with muscle-invasive bladder cancer undergoing neoadjuvant immune checkpoint inhibitor therapy.
The findings suggest that higher baseline TMB is associated with a greater likelihood of pathological complete response as well as improved long-term survival outcomes. Although additional prospective validation is needed, this study provides further evidence that TMB may help identify patients who are more likely to benefit from neoadjuvant immunotherapy and highlights its potential role in future biomarker-driven treatment strategies.
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