Abstract 228P
Background
Fulvestrant is one of the standard treatments for first- or second-line endocrine therapy for hormone receptor (HR)-positive metastatic breast cancer (MBC). We investigated whether the addition of palbociclib to fulvestrant was effective and safe in patients with HR-positive MBC and advanced breast cancer (ABC) who relapsed with fulvestrant monotherapy.
Methods
Patients were primary registered during fulvestrant treatment as 1st or 2nd endocrine therapy. Patients were secondary registered when patients had disease progression during fulvestrant monotherapy and received fulvestrant and palbociclib as the study treatment. The primary endpoint was progression free survival(PFS) from the start of the study treatment. The secondary endpoints included the time to treatment failure(TTF) from the start of the study treatment and adverse events. Our null hypothesis was a median PFS of 5 months, which was the value reported in the PALOMA 3 study. Assuming the median PFS of 8 months for the alternative hypothesis, 63 patients were required to reject the null hypothesis with 80% power under a one-sided alpha of 0.05. (UMIN 000029294).
Results
Between January, 2018 and February, 2020, we enrolled 167 patients from 55 institutions as 1st registration. However, nine cases were excluded from analysis for not meeting inclusion criteria. Of these, 72 patients were enrolled in 2ndary registration. Median follow up time were 23.8 months from 1st registration and 8.9 months from 2nd registration. Median PFS of the study treatment in patients with resistance to fulvestrant monotherapy was 9.4 months (90% Confidence interval 6.9- 11.2 months, p<0.001). TTF from 2nd registration was 7.2 months (90% CI 5.5- 10.4 months). No new adverse events were observed.
Conclusions
Our data suggest that palbociclib plus fulvestrant beyond disease progression to fulvestrant monotherapy is possibly effective and safe in patients with HR-positive HER2-negative ABC/MBC.
Clinical trial identification
UMIN 000029294.
Editorial acknowledgement
Legal entity responsible for the study
JBCRG (Japan Breast Cancer Reserch Group).
Funding
AstraZeneca K.K.
Disclosure
K. Watanabe: Financial Interests, Personal, Invited Speaker: Pfizer, Lilly, Chugai, Kyowa-Kirin, Novartis. N. Niikura: Financial Interests, Institutional, Research Grant: Chugai, Pfizer, Eisai, Mochida, Daiichi Sankyo, Novartis, Lilly; Financial Interests, Personal, Invited Speaker: Chugai, Lilly, Novartis, Daiichi Sankyo, AstraZeneca, Pfizer, Eisai. Y. Kikawa: Financial Interests, Personal, Advisory Role: Daiichi Sankyo; Financial Interests, Personal, Invited Speaker: AstraZeneca, Novartis, Taiho, Chugai, Daiichi Sankyo, Eisai, Kyowa. M. Oba: Non-Financial Interests, Personal, Advisory Role: JBCRG. K. Kobayashi: Financial Interests, Personal, Invited Speaker: Pfizer, Chugai, Lilly, Taiho, Kyowa, Novartis, Eisai, AstraZeneca. H. Tada: Financial Interests, Personal, Invited Speaker: Chugai, Pfizer, Lilly, Daiichi Sankyo. U. Toh: Financial Interests, Personal, Invited Speaker: Daiichi Sankyo, Pfizer, Chugai, Kyowa Kirin. Y. Yamamoto: Financial Interests, Institutional, Funding: Chugai, Kyowa-Kirin, Eisai, Daiichi Sankyo, Nippon-Kayaku, Taiho, Takeda, Lilly, Pfizer, Novartis; Financial Interests, Personal, Invited Speaker: AstraZeneca, Chugai, Kyowa-Kirin, Novartis, Lilly, Pfizer, Daiichi Sankyo, Nippon-Kayaku, Taiho, Eisai, Takeda; Financial Interests, Personal, Advisory Board: AstraZeneca, Chugai, Novartis, Lilly, Pfizer, Daiichi Sankyo; Non-Financial Interests, Personal, Member of the Board of Directors: Japanese Breast Cancer Society; Financial Interests, Personal, Member of the Board of Directors: Japan Breast Cancer Research Group. T. Takeshita: Financial Interests, Personal, Invited Speaker: Pfizar. H. Ishiguro: Financial Interests, Personal, Invited Speaker: Kyowa-Kirin, EP-Force, Chugai, Eisai, Pfizer, JMS, Taiho, Daiichi Sankyo. N. Masuda: Financial Interests, Institutional, Research Grant: Chugai, Lilly, AstraZeneca, Pfizer, Daiichi Sankyo, MSD, Eisai, Novartis, Sanofi, Kyowa-Kirin, Nippon-Kayaku; Financial Interests, Personal, Invited Speaker: Chugai, Pfizer, AstraZeneca, Lilly, Eisai; Non-Financial Interests, Personal, Leadership Role, Representative director: JBCRG. S. Saji: Financial Interests, Personal, Invited Speaker: Eli Lilly, Chugai, AstraZeneca, Kyowa Kirin, Daiichi Sankyo, Taiho, Pfizer, MSD, Novartis, Eisai; Financial Interests, Institutional, Research Grant: Taiho, Eisai, Chugai, Takeda, Daiichi Sankyo; Financial Interests, Institutional, Invited Speaker: MSD, Daiichi Sankyo, Chugai, AstraZeneca; Non-Financial Interests, Invited Speaker: Japanese Breast Cancer Society, Japanse Society of Medical Oncology, Japan Breast Cancer Research Group, Breast International Group. All other authors have declared no conflicts of interest.