Clinical utility of ctDNA as a tool to detect triple-negative breast cancer relapses: The CUPCAKE trial.
Authors: Bidard Francois Clement , Berger Frederique , Arnedos Monica , Mouret-Reynier Marie-Ange , Tredan Olivier , Sabatier Renaud , Jacot William , Massard Vincent , De La Motte Rouge Thibault , Gligorov Joseph , Teixeira Luis , Fiteni Frédéric , Grenier Julien , Dalenc Florence , Buvat Irène , Mechta-Grigoriou Fatima , Kiavue Nicolas 
Published: June 2024

TPS1139 Background: The current follow-up of triple-negative breast cancer (TNBC) patients at high risk of relapse does not involve any blood or imaging monitoring to detect metastases, because of the low sensitivity and specificity of blood and imaging biomarkers in that context. In contrast, ctDNA detection techniques are highly specific, sensitive and can detect a molecular relapse several months before the occurrence of symptoms (1). We hypothesize that the early detection of molecular relapse by ctDNA combined with whole-body mapping of tumor recurrence sites by 68Ga-FAPI-46-PET/CT will enable the detection of relapses when they are still limited in size and number of sites. Detecting oligometastatic relapses could demonstrate a clinical utility by (i) allowing the use of local treatments in addition to systemic treatments; (ii) taking advantage of the higher efficacy of immunotherapy in patients with limited tumor burden and inflammation. Methods: CUPCAKE is a randomized, non-comparative, multicenter trial promoted by Institut Curie (Paris, France), which design is inspired from the Trials WIthin CohortS approach (2). N=450 non-metastatic TNBC patients at high risk of relapse will be included after having signed a written informed consent in a cohort allowing them to be followed by ctDNA monitoring. For each included patient, a ctDNA detection assay (FoundationOne Tracker) will be performed every 3 months, with a turnaround time of less than 3 weeks. When negative, ctDNA detection results will not be disclosed to patients nor clinicians. If, at any timepoint, ctDNA is detected (molecular relapse), patients will be randomized in a 1:1 ratio between the experimental arm (ctDNA-based intervention) and the control arm (no intervention). In the experimental arm, the positive ctDNA result will be disclosed. To locate metastatic foci, patients will be offered to undergo whole-body imaging with 18F-FDG and 68Ga-FAPI-46-PET/CT, in addition to any other workup considered as relevant by their treating physician. If/when a clinical/radiological relapse is observed, systemic or local treatments will be decided by physicians (standard of care). In the control arm, patients and their treating physician will not be made aware of the molecular relapse and will continue the standard surveillance with repeated ctDNA test every 3 months (blinded). At the time of the clinical/radiological diagnosis of relapse, similar procedures will be performed (18F-FDG & 68Ga-FAPI-46-PET/CT). The primary endpoint is overall survival rate at 24 months after the randomization in the experimental arm while the control arm will serve as reference. Secondary endpoints include efficacy criteria like progression-free survival but also clinical features upon radiological/radiological relapse, or performance criteria of 68Ga-FAPI-46 versus 18F-FDG PET/CT. 1. Coombes, Clin Cancer Res. 2019. 2. Relton, BMJ. 2010. Clinical trial information: 06225505.