VENTANA is a phase 0 multicenter, window of opportunity, three-arm, randomized clinical trial of oral metronomic vinorelbine (VNB) and letrozole versus either treatment alone in postmenopausal women with newly diagnosed untreated HR+ and HER2-negative, stage I-III operable breast cancer. Other eligibility criteria include primary tumor size 1 cm (cT1-3) and N0-1, ECOG PS 0-1 and evaluable diagnostic tumor sample.~Primary objective is to test if Oral Metronomic Vinorelbine and Letrozole induce a superior anti-proliferative effect than either drug alone in patients with early breast cancer defined as Luminal by PAM50/HER2-negative. This will be evaluated by measuring the expression of 11 proliferative genes contained in the PAM50/Prosigna® array (BIRC5, CCNB1, CDC20, CDCA1, CEP55, KNTC2, MKI67, PTTG1, RRM2, TYMS and UBE2C), as surrogate biomarker of its anticancer activity. By evaluating other breast cancer-related gene signatures (560 genes), the antiangiogenic and immunogenic potential of treatment arms will be compared and other genes regulated in a treatment-specific manner identified. These analyses will be performed in different PAM50-defined subtypes (Luminal, LuminalA or LuminalB). Clinical efficacy and safety of treatments will also be evaluated.~Patients will first undergo screening and mandatory collection of core tumor biopsies for study analysis. Patients are randomized (1:1:1) to receive Letrozole 2.5mg daily, oral Vinorelbine 50mg 3 days a week or Letrozole 2.5mg daily and oral Vinorelbine 50mg 3 times a week. After 3 weeks of treatment, patients will undergo surgery, and both pre-treatment and post-treatment surgery samples will be analyzed. Alternatively, if surgery will be delayed, a tumor core biopsy will be collected. Anyway, post-treatment sample should be collected within 5 days after end of treatment in order to observe the biological response.~Axillar and mammary surgery will be done according to local standards; however, sentinel lymph node biopsy previous to surgery is not permitted. Following surgical excision, adjuvant treatment will be as per investigator´s choice and local standards of care outside the scope of this protocol. End of study is 28 days (±3 days) after last study drug dose with a safety follow-up visit.
VENTANA is a window-of-opportunity trial that will explore whether, similar to CDK4/6 inhibitors, Oral Metronomic Vinorelbine in combination with Letrozole induces a superior anti-proliferative effect than Letrozole alone.