Efficacy and safety of palbociclib plus fulvestrant in Asian women with hormone receptor-positive (HR+)/human epidermal growth factor-2 negative (HER2-) metastatic breast cancer (MBC) that progressed on prior endocrine therapy (ET)

Aim/Background

Endocrine resistance is a major clinical issue for patients (pts) with HR + /HER2- breast cancer. The standard of care (SOC) is to re-challenge with ET before switch to chemotherapy (CT). PALOMA3 assessed whether Palbociclib (P) + fulvestrant (F) prolonged progression-free survival (PFS) vs F + placebo (PLB) in pts with HR + /HER2- MBC whose disease had progressed on prior ET. Primary analysis showed median PFS of 9.2 vs 3.8 m (HR 0.42, P < 0.001) in full population (Turner et al NEJM 2015). We present the efficacy and safety in Asian pts with longer follow-up.

Methods

In the Ph 3 PALOMA3 study, 521 pts were randomized 2:1 to P (125 mg/d oral [3 wks drug, 1 wk off]) + F (500 mg, SOC) or PLB + F. Pre-/perimenopausal pts also received goserelin. One previous line of CT for MBC was allowed. Safety assessments occurred at baseline and on D1 per cycle; blood counts every 2 wks for first 2 cycles and on D1 of subsequent cycles. Primary endpoint was investigator-assessed PFS. Secondary endpoints: overall survival, response assessment, patient-reported outcomes, safety. PALOMA3 enrolled pts in Korea and Japan.

Results

By March 2015, 105 Asian pts were randomized (P + F, 74; PLB + F, 31). Baseline characteristics were well balanced. Compared to non-Asians, median age was lower in Asians (52 vs 58 y) and more were pre/perimenopausal (42% vs 15%). 59% of Asian pts had visceral disease, 80% had documented endocrine responsiveness, 34% had 1 line of CT for MBC. Median PFS in Asian pts was not reached for P + F (95% CI 9.2–NR) and 5.8 m for PLB + F (3.5–9.5m) (HR 0.485 [95% CI 0.270–0.869], P = 0.0065). Most common Grade 3/4 adverse events (AEs) in Asian pts were neutropenia (92%) and leucopenia (29%); febrile neutropenia occurred in 4.1% (P + F). No pt stopped P + F due to AEs. 51% of Asian pts had dose reduction due to AEs. 48% were on 100 mg dose.

Conclusions

P + F improved PFS in Asians with HR + /HER2- MBC that progressed on prior ET. The safety profile was consistent with that seen in Non-Asians; neutropenia was the most common AE, and can be managed by dose reduction. P + F may be a reasonable therapeutic option in Asian pts.

Clinical trial identification

NCT01942135

Disclosure

J. Ro: served as a consultant/advisor to Nippon Kayaku (NK) and received travel support from Eisai.

S.-A. Im: consulting fees (e.g. advisory boards): Roche, Novartis, AstraZeneca; Contracted Research: AstraZeneca in 2014. N. Masuda: fees for Non-CME Services received directly from commercial interest or their agents (speaker's Bureaus): Chugai, AstraZenaca Contracted Research Chugai, Novaltis, Pfizer, AstraZeneca, Lilly. K. Inoue: research funding from Pfizer, Lilly, Chugai, Taiho, Daiichi-Sankyo, Parexel. K. Zhang, C. Giorgetti, P. Schnell, C. Huang Bartlett: employee of and owns stock in Pfizer Inc and receive stock options from Pfizer Inc. H. Iwata: honoraria from AstraZeneca, Eisai, Daiichi-Sankyo, Chugai, and Pfizer Inc. All other authors have declared no conflicts of interest.