286TiP - Phase II randomized trial of neoadjuvant trastuzumab and pertuzumab (TP) with either palbociclib + letrozole (Pal+L) or paclitaxel (Pac) for elderly patients with estrogen receptor & HER2 positive (ER+/HER2+) breast cancer (BC) (International Breast Cancer Study Group IBCSG 55-17, TOUCH)

Abstract

BackgroundHER2 blockade in combination with chemotherapy (CT) remains the treatment of choice for patients with early HER2+ BC, irrespective of ER status. Patients with HER2+ early BC co-expressing ER may benefit from HER2 blockade in combination with endocrine therapy (ET) and new targeted agents. Elderly patients benefit from HER2 blockade as much as younger ones but they have higher risks of adverse events, mostly induced by the CT partner, making de-escalation of CT appealing. Recent data have elucidated cyclin-dependent kinases 4 and 6 (CDK4/6) as key therapeutic targets functioning downstream of both ER and HER2 pathways suggesting CDK4/6 inhibitors like Pal may be ideal partners for ET in this context. Pre-clinical and clinical data suggest that a gene signature of functional loss of Retinoblastoma (RBsig) might predict sensitivity to CT vs CDK4/6i in ER+/HER2+ early BC. The TOUCH hypothesis is that neoadjuvant therapy with Pal + ET + dual HER2 blockade may be more active in patients with ER+/HER2+ RBsig LOW early BC while those with RBsig HIGH may require CT. Trial designTOUCH is an open-label, multicenter, randomized phase 2 neoadjuvant trial. 144 patients ≥65 years with ER+/HER2+ primary BC will be randomized (1:1) to dual HER2 blockade (5 doses T+P) + either Pal (125mg/d po; 21 of 28d x 4 cycles) + L (daily x 16 weeks), or Pac (80mg/m2 iv, d1,8,15 q28 days x 4 cycles), before surgery. RBsig (HIGH vs LOW) will be determined centrally on mandatory pre-treatment biopsies. Baseline geriatric assessment includes G8, Instrumental Activity of Daily Living, Charlson comorbidity index. The primary objective is to explore the interaction between RBsig and treatment activity assessed by pathological complete response (pCR). Exact logistic regression will test RBsig by treatment interaction (2-sided a=.05) and estimate odds ratios (OR) for pCR. The sample size provides 86% power, assuming an overall pCR rate of 26%, and OR=2.4 vs OR=0.11 for RBsig LOW vs HIGH. Accrual began April 2019. Clinical trial identificationNCT03644186. Legal entity responsible for the studyInternational Breast Cancer Study Group. FundingPfizer, Roche. DisclosureL. Biganzoli: Advisory / Consultancy, consultant and in an advisory role: AstraZeneca; Advisory / Consultancy, consultant and in an advisory role: Celgene; Advisory / Consultancy, consultant and in an advisory role: Eisai; Advisory / Consultancy, consultant and in an advisory role: Genomic Health; Advisory / Consultancy, consultant and in an advisory role: Ipsen; Advisory / Consultancy, consultant and in an advisory role: Lilly; Advisory / Consultancy, consultant and in an advisory role: Novartis; Advisory / Consultancy, consultant and in an advisory role: Pfizer; Advisory / Consultancy, consultant and in an advisory role: Pierre Fabre; Advisory / Consultancy, consultant and in an advisory role: Roche; Research grant / Funding (institution): Celgene; Research grant / Funding (institution): Genomic Health; Research grant / Funding (institution): Novartis. E. Brain: Honoraria (self), receipt of honoraria or consultation fees: Roche; Honoraria (self), receipt of honoraria or consultation fees: Pfizer; Honoraria (self), receipt of honoraria or consultation fees: AstraZeneca; Honoraria (self), receipt of honoraria or consultation fees: BMS; Honoraria (self), receipt of honoraria or consultation fees: Celgene; Honoraria (self), receipt of honoraria or consultation fees: Clinigen; Honoraria (self), receipt of honoraria or consultation fees: Hospira; Honoraria (self), receipt of honoraria or consultation fees: Janssen; Honoraria (self), receipt of honoraria or consultation fees: Mylan; Honoraria (self), receipt of honoraria or consultation fees: OBI Pharma; Honoraria (self), receipt of honoraria or consultation fees: Puma; Honoraria (self), receipt of honoraria or consultation fees: Samsung. L. Malorni: Research grant / Funding (self), research funding and consulting fees: Pfizer. All other authors have declared no conflicts of interest.