"CUPCAKE": Early detection of triple negative breast cancer relapse: a clinical utility trial

The primary objective of the study is to evaluate the efficacy of a **ctDNA-based surveillance strategy** in terms of reducing the risk of early death in patients with **triple-negative breast cancer (TNBC)** who are at high risk of relapse. This is clinically relevant as early detection and intervention could potentially improve survival outcomes in this patient population.

Secondary objectives include:

• Evaluating the efficacy of the surveillance strategy using other endpoints.
• Assessing the prevalence of patients with an altered general condition at relapse.
• Evaluating the safety of the **ctDNA** and **68Ga-FAPI-46 PET-CT** monitoring process.
• Assessing the impact of the surveillance process on patient-reported outcomes.
• Evaluating outcomes in patients who present with a clinical or radiological relapse at the time of or before any **ctDNA** detection.
• Exploring the feasibility of the surveillance process.
• Evaluating the diagnostic performance of the **68Ga-FAPI-46 PET-CT**.
• Exploring the association between patients' characteristics and outcomes.
• Exploring **ctDNA** kinetics upon treatment start after clinical or radiological relapse.
• Characterizing the cancer biology of patients with an early TNBC relapse.
• Exploring the medico-economic correlates of the surveillance strategy procedure.

The clinical trial involves **female** participants aged 18 years and older, diagnosed with **triple-negative breast cancer** (TNBC) at high risk of relapse. The study population is specifically selected to include individuals who have undergone surgery with curative intent for non-metastatic TNBC and have initiated adjuvant therapy. Participants must have a high-risk primary tumor, as defined by specific criteria, and show no signs of local or distant relapse. The trial does not include a vulnerable population, and participants are required to have a performance status of less than 2. The sponsor has not provided information regarding the total number of participants. Participants are expected to comply with protocol requirements, and lifestyle factors such as diet and physical activity are not specified as part of the selection criteria. The trial population was selected based on specific inclusion criteria, ensuring that all participants are covered by health insurance and have signed a written informed consent before inclusion.

The clinical trial is designed to evaluate the efficacy of a **ctDNA-based surveillance strategy** in patients with **triple-negative breast cancer** (TNBC) at high risk of relapse. This is a Phase 4, randomized, double-blind, controlled trial. The trial aims to assess the risk of early death and overall survival rate 24 months after randomization. The trial is expected to run from June 15, 2023, to January 31, 2028, with participant involvement lasting up to 24 months.

Participants will undergo a series of study visits, beginning with an inclusion (screening) visit to confirm eligibility based on criteria such as age, health insurance coverage, and previous treatment history. Eligible participants must be female, aged 18 or older, and have undergone surgery for non-metastatic TNBC. The inclusion visit will also ensure that participants have no signs of local or distant relapse and can comply with protocol requirements.

Following the inclusion visit, participants will be randomized into either the experimental arm, receiving ctDNA analysis and **68Ga-FAPI-46 PET-CT**, or the control arm, following standard surveillance. Follow-up visits will be scheduled to monitor the primary and secondary endpoints, including overall survival, recurrence-free survival, and progression-free survival. The trial will also assess the number of metastatic sites at relapse and the proportion of patients with altered general conditions.

The end-of-study visit will occur at the conclusion of the participant's involvement, where final assessments will be conducted. Participants may be terminated early from the study if they experience significant adverse events, fail to comply with the study protocol, or withdraw consent. The trial will also explore the cost-effectiveness of the combined ctDNA and 68Ga-FAPI-46 PET-CT strategy compared to existing surveillance methods.

The clinical trial involves the administration of the experimental medication **[68Ga]Ga-FAPI-46**, which is formulated for **intravenous infusion**. The active substance in this medication is chemically synthesized and is identified as (S)-2,2',2''-(10-(2-(4-(3-((4-(2-(2-cyano-4,4-difluoropyrrolidin-1-yl)-2-oxoethylcarbamoyl)-quinolin-6-yl)(methyl)amino)-propyl)piperazin-1-yl)-2-oxoethyl)-68Ga-[1,4,7,10]-tetraazacyclododecane-1,4,7-triyl)triacetate. The administration of this compound is conducted via the intravenous route, with a maximum daily dose of 2 MBq/kg and a total maximum dose of 4 MBq/kg over the treatment period. The treatment duration is limited to a maximum of 9 days.

In this study, no non-experimental treatments such as standard-of-care therapy, placebo, or comparator treatments are utilized. The focus is solely on the administration of the experimental drug **[68Ga]Ga-FAPI-46**. Participant compliance with the dosing schedule is monitored to ensure adherence to the protocol. The trial aims to evaluate the efficacy of this compound in the context of early detection of triple-negative breast cancer relapse, as part of a clinical utility trial. The pharmaceutical form and administration route are specifically designed to optimize the delivery and efficacy of the active substance in the target population.

Efficacy in this clinical trial will be assessed primarily through the **overall survival rate** 24 months after randomization. This endpoint will focus on randomized patients, with a non-comparative analysis conducted in the experimental arm, while the control arm serves as a reference. Secondary endpoints include the number of metastatic sites at the time of clinical or radiological relapse, **recurrence-free survival** (RFS), **progression-free survival** (PFS), first-line PFS (1L-PFS), second-line PFS (2L-PFS), and the best overall response rate (ORR). Additionally, overall survival will be measured from randomization, not limited to the first 24 months.

Further assessments will include the proportion of patients presenting with an altered general condition (performance status ≥2) at the first evidence of clinical or radiological relapse, and adverse events (AEs) and serious adverse events (SAEs) related to either ctDNA analysis or **68Ga-FAPI-46 PET-CT**, reported by rate and grade according to NCI CTC-AEs v5.0. Quality of life will be evaluated using the QLQ-C30 questionnaire with the QLQ-BR45 module at various stages, including inclusion, molecular relapse in the experimental arm, radiological/clinical relapse in the standard arm, and during post-relapse follow-up.

Exploratory endpoints will investigate the rate of ctDNA analysis technical failures, ctDNA analysis turnaround time, and the rate of 68Ga-FAPI-46 PET-CT technical failures. Additional exploratory analyses will include associations between quantitative and qualitative results of the primary tumor genomic landscape, digital pathology features, ctDNA detection, 68Ga-FAPI-46 PET-CT results, patient characteristics, and outcomes. Quantitative changes in ctDNA levels will be monitored at three, six, and nine months after treatment start in relapsed patients. Supplemental molecular analyses will be performed on banked plasma and optional biopsies at relapse, with centralized tissue sections for additional image analyses at the study's conclusion. A cost-effectiveness analysis of 68Ga-FAPI-46 PET-CT combined with ctDNA compared to existing surveillance strategies will also be conducted.