Palbociclib in clinical use for metastatic breast cancer at a single institution

Abstract

Abstract Background The PALOMA2/3 trials demonstrated prominent efficacy of combination therapy of palbociclib (PAL) and endocrine therapy (ET) compared with monotherapy. PAL was approved for metastatic breast cancer in Japan in 2017. We evaluated the efficacy and safety in practice after approval of PAL in Japan. Methods We retrospectively reviewed patients who newly received PAL at Aichi Cancer Center after Dec 2017. The patients were classified by treatment-line and assessed as follows; clinical benefit rate (CBR) defined as the rate of clinical PR, CR and long SD (more than 6 months) based on physician’s judgment, time to failure (TTF) defined as the duration time of PAL, prior ET response, and adverse events (AEs). TTFs were figured with swimmer’s plot by treatment-line, PAL doses (125, 100, 75mg/day). Results Between Dec 2017 and Oct 2018, 64 patients were eligible. Median age was 62.5 (37-82). Forty-one patients (64%) had visceral metastasis. PAL was administered for 1st to 3rd line (early-line group) in 52% (n\u2009=\u200933), and for more than 4th line (late-line group) in 48% (n\u2009=\u200931). Combination ETs were aromatase inhibitors (n\u2009=\u200927, 42%), fulvestrant (n\u2009=\u200935, 55%), and tamoxifen (n\u2009=\u20092, 3%). Prior ET was sensitive in 59% (n\u2009=\u200933). The dose reduction was needed in 62% (100mg; n\u2009=\u200919, 75mg; n\u2009=\u200921). Twenty-eight patients (43.8%) were continuing PAL. Overall CBR was 38%. By treatment line, CBR was 51.6% in the early-line group, and 22.6% in the late-line group. Median TTF was 4.6 months (0.2-10.2). There were no significant differences of TTF by treatment-line, prior ET response, and PAL doses. The grade 3-4 hematological toxicity, such as neutropenia and anemia, were observed in 83% (n\u2009=\u200953). Stomatitis, nausea, and fatigue were common, but most of them were grade 1-2. No patients discontinued PAL due to AEs. Conclusions In the clinical setting, PAL was given in many late line-patients who were not eligible for the PALOMA2/3 trials. Its efficacy was not sufficient, although it was feasible.