Letrozole and palbociclib versus 3rd generation chemotherapy as neoadjuvant treatment of minal breast cancer. Results of the UNICANCER-eoPAL study

Abstract

Background: Benefit of neoadjuvant chemotherapy in patients (pts) with luminal breast cancer (LBC) is limited. Palbociclib combined with endocrine treatment has shown impressive results in advanced LBC. We conducted a randomized parallel phase II study, assessing letrozole + palbociclib (LP) as neoadjuvant treatment in LBC. Methods: Postmenopausal women were eligible if they had a stage II‐III ER‐positive HER2‐negative BC, not candidate for breast conserving surgery (BCS), with either a PAM50 luminal B, or a PAM50 luminal A profile with proven lymph node involvement (N+). A parallel 1:1 randomization proposed 6 courses of 3rd generation chemotherapy (FEC100 x 3 ‐ docetaxel 100 x 3), or 19 weeks (wks) of L 2.5 mg/day plus P 125 mg/day, 3 wks/4. Surgery was performed at wk 20. Primary endpoint was locally assessed Residual Cancer Burden (RCB) rate. Main secondary endpoints included safety, response rate, positive and negative predictive values of PAM50 ROR (risk of recurrence)‐ defined status, centrally reviewed RCB, and BCS rates. The protocol planned that the trial should be stopped for futility if <0.001). Conclusions: Neoadjuvant LP led to a slightly lower pCR/RCB 0‐I rate than chemo, however clinical response and BCS rates were similar in both arms and LP had a much better safety profile. Extensive analyses are ongoing.