Neoadjuvant endocrine therapy with or without palbociclib in low-risk patients: a phase III randomized double-blind SAFIA trial.

Background: The most prevalent subtype of breast cancer (BC) is luminal hormonal-positive breast cancer. The neoadjuvant chemotherapy regimens have side effects, emphasizing the need to identify new startegies.

Objective: Analyze the complete pathologic response (pCR) rate and overall response in a low-risk hormone-positive subset of patients receiving neoadjuvant hormone treatment (NAHT) with or without Palbociclib (a CDK4/CDK6 inhibitor) to boost NAHT effectiveness.

Materials And Methods: Based on the upfront 21-gene Oncotype DX or low-risk Breast Recurrence Score assay (RS™), the SAFIA trial is designed as a prospective multicenter international, double-blind neoadjuvant phase-III trial that selects operable with luminal BC patients that are HER2-negative for the induction hormonal therapy with Fulvestrant 500 mg ± Goserelin (F/G) followed by randomization of responding patients to palbociclib versus placebo. The pCR rate served as the study's main outcome, while the secondary endpoint was a clinical benefit.

Results: Of the 354 patients enrolled, 253 initially responded and were randomized to either F/G fulvestrant with palbociclib or placebo. Two hundred twenty-nine were eligible for the evaluation of the pathologic response. No statistically significant changes were observed in the pCR rates for the patients treated with the F/G therapy with placebo or palbociclib (7% versus 2%, respectively) per the Chevallier classification (Class1 + Class2) (p = 0.1464) and 3% versus 10% assessed per Sataloff Classification (TA, NA/NB) (p = 0.3108). Palbociclib did not increase the rate of complete pathological response.

Conclusion: Neoadjuvant hormonal therapy is feasible in a selected population with a low RS score of < 31 CLINICAL TRIAL: NCT03447132.