|The following article features coverage from the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, Illinois. Click here to read more of Cancer Therapy Advisor‘s conference coverage.|
Single-agent palbociclib added to current endocrine therapy improves outcomes among women with hormone receptor positive (HRplus), HER2 negative (HER2-) metastatic breast cancer (MBC) who progress on endocrine therapy (ET), according to data from the TREnd trial (ClinicalTrials.gov Identifier: NCT02549430) presented at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago.1
“Preclinical data suggest that adding palbociclib to endocrine therapy may reverse acquired endocrine resistance,” presenter Luca Malorni, MD, from the Istituto Toscano Tumori in Prato, Italy, said.
TREnd was a randomized phase 2 study which enrolled 115 women with HRplus/HER2- MBC whose disease progressed on 1 or 2 prior ETs.
Fifty-seven patients were randomly assigned to the palbociclib only arm and received palbociclib 125 mg daily (3 weeks on, 1 week off); 58 were randomly assigned to receive palbociclib plus ET.
The primary endpoint was clinical benefit rate (CBR: complete response [CR], partial response [PR], or stable disease for longer than 6 months [SD]).
At baseline, more than 70% of patients had visceral disease; about 69% had received 1 line of prior ET. Across each arm of the study, 67% received study treatment as second-line ET and 33% as third line.
CBR was similar for patients across both arms of the study: 54% for palbociclib plus ET and 60% for palbociclib alone.
Median duration of clinical benefit was significantly longer for patients receiving the combination of palbociclib plus ET: 11.5 vs 6 months for palbociclib alone; P = .0021). Progression-free survival (PFS) was longer, but not significantly longer, for patients on palbociclib plus ET: 10.8 vs 6.5 months.
Although palbociclib plus ET was not associated with significantly longer PFS, patients receiving palbociclib plus ET due to secondary ET resistance (defined as prior ET for longer than 6 months) had significantly longer PFS (11.5 vs 65.5 months for palbociclib alone; P = .02).
No new safety signals were seen in the study.
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“Despite no difference seen in CBR, the PFS and related subgroup analyses by duration of prior ET suggests that palbociclib could reverse acquired resistance to the same endocrine agent used in prior line of ET,” Dr Malorni concluded.
Read more of Cancer Therapy Advisor‘s coverage of the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting by visiting the conference page.
- Malorni L, Curigliano G, Minisini AM, et al. A phase II trial of the CDK4/6 inhibitor palbociclib (P) as single agent or in combination with the same endocrine therapy (ET) received prior to disease progression, in patients (pts) with hormone receptor positive (HRplus) HER2 negative (HER2-) metastatic breast cancer (mBC) (TREnd trial). J Clin Oncol. 2017;34(suppl; abstr 1002).