435TiP - Molecular imaging of programmed death ligand 1 (PD-L1) expression with [89Zr]Zr-atezolizumab positron emission tomography/computed tomography (PET/CT) in patients with metastatic triple negative breast cancer (mTNBC): The MIMIR-study

Background

Treatment with PD-L1 or PD-1 targeting antibodies is a cornerstone in cancer therapy, but not all patients benefit from these drugs. For most indications, the current reference biomarker is PD-L1 expression in a tumor biopsy, but this method has several disadvantages. Molecular imaging, such as PET/CT using receptor-specific radiotracers, offers non-invasive, real-time visualization of treatment targets. Previous trials have explored a few PD-L1/PD-1 radiotracers but lacked a systematic approach focused on a single tumor type and standardized clinical management.

Trial design

The MIMIR-trial (EU CT 2022-500808-21-00, NCT05742269) involves newly diagnosed mTNBC patients planned for first-line systemic treatment. Participants undergo a PD-L1 PET/CT scan with [89Zr]Zr-atezolizumab followed by a biopsy, with results guiding subsequent treatment with chemotherapy (carboplatin and nab-paclitaxel), combined with atezolizumab based on PD-L1 status as determined by IHC and/or PET. Treatment effectiveness is assessed bi-monthly, and therapy is continued until disease progression or unmanageable toxicity. The primary aim is to determine the statistical concordance (Cohen’s kappa coefficient) between PD-L1 status by PET and IHC. To target a kappa of 0.80 with a precision of +/- 0.15, 64 patients are required in this study. Secondary objectives include evaluating the predictive value of PD-L1 PET for treatment response and development of immunotherapy-mediated toxicity. Tissue, feces, and blood samples are collected for further translational analysis. The trial is ongoing at Karolinska University Hospital in Stockholm, Sweden, with three patients enrolled so far. An additional cohort of patients with non small cell lung cancer will be opened during Q3-4 2024.

Clinical trial identification

EU CT 2022-500808-21-00, NCT05742269.

Editorial acknowledgement

Legal entity responsible for the study

Karolinska University hospital, Region Stockholm, Sweden.

Funding

Roche Sweden AB.

Disclosure

J. Bergh: Non-Financial Interests, Personal, Advisory Board: stratipath. All other authors have declared no conflicts of interest.