To Identify Primary Resistance to CDK4/6 Inhibitors in Breast Cancer

Recruiting

• Conditions: Metastatic Breast Cancer; HER2-negative Breast Cancer; ER Positive Breast Cancer
• Interventions: Diagnostic Test: Thymidine kinase activity

• Registration Number: NCT04660435
• Lead Sponsor: Fondazione Sandro Pitigliani

Brief Summary

This is a multi-center biomarkers study aiming to prospectively collect biological samples from patients with ER+ and HER2-negative metastatic breast cancer, who are candidate to first-line treatment with an aromatase inhibitor and a CDK4/6 inhibitor as per standard clinical practice.

Blood and tissue samples will be collected for biomarker analysis, including thymidine kinase1 activity, gene expression signatures and circulating tumor DNA.

Detailed Description

Enrolled patients will receive first-line treatment with a CDK4/6 inhibitor + AI (anastrozole, letrozole or exemestane) in accordance with local practice. No drugs will be provided by the study Sponsor. Following disease progression on first-line therapy, subsequent, second-line therapy will be administered at physician discretion and as per physician choice.

For all participating patients, serum and plasma samples will be collected at the following time-points:

* Baseline (\< 2 weeks before treatment)

* During treatment with CDK4/6 inhibitors + AI: at day 15 (+/- 2) of the first cycle, day 1 (+/-2) of cycle 2, day 1 (+/- 2) of the cycle closest to the first trial-mandated tumor evaluation (after 12-18 weeks from study inclusion), day 1 (+/- 2) of cycle 6, and every 6 cycles thereafter

* At disease progression or permanent discontinuation of CDK4/6 inhibitors + AI (within 35 days from last CDK4/6 inhibitor dosing)

* During the immediate subsequent treatment (second line) (any type, as per physician choice): at day 1 (+/- 2) of cycle 1 (if \> 7 days from last CDK4/6 inhibitors dosing), at day 1 of cycles 3, 6 and every 6 cycles thereafter

* At disease progression or permanent discontinuation of second line treatment (within 35 days from last dosing)

One sample of whole blood will be collected at baseline.

All blood samples will be taken concomitantly with blood draws for routine clinical practice.

To be eligible for the study, availability of material from one formalin fixed and paraffin embedded (FFPE) tumor block from a baseline biopsy of a metastatic site taken before starting treatment is mandatory. Although not mandatory for inclusion, material from an archival FFPE tumor block from the primary breast tumor must also be provided, whenever available. Additionally, material from one FFPE tumor block of a tissue biopsy from a metastatic site collected upon disease progression to first-line treatment with CDK4/6 in and AI will be collected whenever possible

Study Timeline

• Study Start: 2020-09-01
• Study First Submitted: 2020-12-03
• Study First Submitted QC: 2020-12-03
• Study First Posted: 2020-12-09
• Status Verified: 2025-02
• Last Update Submitted: 2025-02-25
• Last Update Posted: 2025-02-26
• Primary Completion: 2025-12-01
• Study Completion: 2026-12-01

Recruitment & Eligibility

• Status: RECRUITING
• Sex: Female
• Target Recruitment: 150

Inclusion Criteria

1. Women aged 18 years or older, with a diagnosis of metastatic breast cancer

2. ER-positive and HER2-negative disease as assessed locally either on primary tumor tissue or on a biopsy of a metastasis

3. The patient has not received any prior systemic therapy for metastatic breast cancer (may have received prior hormonal therapy or chemotherapy in the neo/adjuvant setting)

4. The patient is candidate to receive first-line therapy with an aromatase inhibitor (AI) and a CDK4/6 inhibitor per local clinical practice

5. The patient must have evaluable disease according to RECIST 1.1 (either measurable or non-measurable).

   Note: Patients with bone-only disease will be allowed in a specific sub-cohort, which will comprise 10% of the total sample size.

6. Hystologic material from one formalin-fixed, paraffin-embedded (FFPE) tumor block from a diagnostic core or excisional biopsy of a metastatic lesion, taken before study entry must be provided (patients with bone-only disease will be accepted into the trial without a biopsy of the metastatic site). Hystologic material from an additional biopsy (core or excisional) taken at time of disease progression on the study treatment must also be provided, if clinically feasible. When available, hystologic material from an FFPE tumor block from the primary breast cancer must also be submitted.

7. The patient agrees to provide blood samples. at the trial specified time points

Exclusion Criteria

1. Patients with metastatic disease isolated to the central nervous system (CNS) without metastatic involvement of any other site, unless surgical excision of CNS metastasis has been performed and the tumor tissue is available for the study.
2. Previous or current non-breast malignancies within the last 5 years, with the exception of in situ carcinoma of the cervix and/or adequately treated basal cell or squamous cell carcinoma of the skin

Study & Design

• Study Type: OBSERVATIONAL
• Study Design: Not specified

Arm && Interventions

Group	Intervention	Description
Women with ER+/Her2 negative metastatic breast cancer	Thymidine kinase activity	Patients with ER+/HER2-negative metastatic breast cancer candidate to first-line treatment with a CDK4/6 inhibitor and an aromatase inhibitor as per standard clinical practice

Primary Outcome Measures

Name	Time	Method
Progression free survival	5 years	time from inclusion date to date of first documentation of progression or death due to any cause, whichever occurs first

Secondary Outcome Measures

Name	Time	Method
Clinical benefit rate	5 years	Complete Response, Partial Response, or Stable Disease ≥24 weeks

Trial Locations

Locations (1)

Hospital Santo Stefano; 🇮🇹 Prato, Tuscany, Italy