This is a single-centre study comprising two phases: a lead-in phase Ib and a phase II randomized portion. Lead-in Phase Ib study A lead-in phase I study will be built into this protocol to confirm the dose of lenvatinib that can safely be combined with letrozole. We expect that the optimal phase II dose level will be determined after recruiting 12-18 subjects into phase Ib. This dose level will be the one to be tested in the phase II portion of the study. Phase II open label study In this part of the study, eligible patients will be treated with single agent lenvatinib at the phase II recommended dose for 2 weeks, followed by lenvatinib combined with letrozole 2.5mg daily for 12 weeks. A total of 30 patients with ER positive breast cancer and measurable primary tumor will be enrolled over a period of 24-30 months
Hypothesis: We hypothesize that combining a RET inhibitor such as lenvatinib with endocrine therapy may potentiate anti-tumor effects in ER+ breast cancers in the clinic. Given that RET inhibition is the primary mechanism of action of lenvatinib, we further hypothesize that RET expression in the breast tumor may be a biomarker that predicts for better response to the combination of a RET inhibitor and endocrine therapy in both a neoadjuvant (Part A) and a metastatic (Part B) setting. Primary Objectives 1. To confirm the dose of lenvatinib that can be safely combined with letrozole in the lead-in Phase Ib part of the study. 2. Part A (For patients with non-metastatic breast cancer undergoing neoadjuvant treatment) : To determine the overall clinical response (measured by ultrasound) and pathological complete response rate after 2 weeks of neoadjuvant single agent lenvatinib followed by 12 weeks of letrozole combined with lenvatinib and compare with historical controls treated with single agent letrozole. 3. Part B (For patients with metastatic breast cancer and who have tumor lesion that can be serially biopsied safely): to determine the clinical response (measured by RECIST criteria) after 2 weeks of single agent lenvatinib followed by continuous dual therapy of lenvatinib and letrozole, until time of progression or intolerability. Secondary Objectives 1. To evaluate the overall biological effects (Ki67 changes, histological response, apoptosis, RET and downstream targets such as AKT and ERK) of 2 weeks of single agent lenvatinib, and of letrozole + lenvatinib, in ER positive breast cancer, respectively. 2. To identify biological predictors for treatment response to letrozole + lenvatinib in ER positive breast cancer using pharmacokinetics, pharmacogenetics, genomics and proteomics strategies. 3. To compare the following parameters between RET positive versus RET negative, ER positive breast cancer: * Part A : i. Clinical response (measured by ultrasound) and biological effects of 2 weeks of single agent lenvatinib, ii. Clinical response (measured by ultrasound) and biological effects after 2 weeks of single agent lenvatinib followed by 12 weeks of letrozole combined with lenvatinib -Part B : i. Clinical response measured by RECIST criteria after 2 weeks of single agent lenvatinib followed by letrozole combined with lenvatinib ii. Progression-free and overall survival with letrozole combined with lenvatinib
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
TREATMENT
Masking
NONE
Enrollment
40
Single agent lenvatinib daily continuously x 2 weeks, followed by letrozole 2.5mg daily + lenvatinib x 12 weeks. Lumpectomy or mastectomy should be considered after completing 14 weeks of pre-operative lenvatinib + letrozole for curative intent in non-metastatic patients and for local control for patients with metastatic disease. If surgery is planned, it should preferably be performed within 2-12 weeks after completing neoadjuvant endocrine therapy, and after toxicities (if any) from the neoadjuvant endocrine therapy have resolved. If the patient is deemed inoperable after 14 weeks of lenvatinib + letrozole, a final biopsy will be obtained, and the patient discontinued from the study and treated as per standard clinical practice by the treating physician.
National University Hospital
Singapore, Singapore, Singapore
Rates of clinical response
Complete and partial clinical response, including confidence intervals.
Time frame: 2-3 weeks
Rates of pathological complete responses.
A pathological complete responder is defined as any patient who demonstrates no histological evidence of invasive tumor in the primary breast site as well as in resected axillary lymph nodes
Time frame: 4-6 weeks
Progression-free survival
Time to documented disease progression is defined as the time from the date of study enrollment to the first date of documented disease progression. Time to documented disease progression will be censored at the date of death for patients who have not had documented disease progression. For patients who are still alive at the time of analysis and who have not had documented disease progression, time to documented disease progression will be censored at the date of the last follow-up visit.
Time frame: 2 - 5 year
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