SABCS 2021: Final Results of PALLAS Trial on Palbociclib Plus Endocrine Therapy in HER2-Negative Breast Cancer
Posted: Friday, December 10, 2021
The phase III PALLAS trial, conducted by Michael Gnant, MD, of the Medical University of Vienna, and colleagues, evaluated whether the addition of the CDK4/6 inhibitor palbociclib to adjuvant endocrine therapy would improve clinical outcomes versus endocrine therapy alone in patients with hormone receptor (HR)-positive, HER2-negative breast cancer. Their final study results were presented during the 2021 San Antonio Breast Cancer Symposium (SABCS; Abstract GS1-07).
“With the full number of events, this analysis of the PALLAS trial shows that the addition of 2 years of palbociclib to ongoing adjuvant endocrine therapy did not improve survival endpoints for patients with stage II to III HR-positive/HER2-negative early breast cancer,” concluded the researchers. “Whether palbociclib is beneficial in the adjuvant setting for certain subgroups of patients will be further evaluated with longer-term follow-up and by the ongoing translational science program.”
This open-label trial enrolled 5,761 patients with stage II to III, HR-positive/HER2-negative early breast cancer. Participants were randomly assigned to receive either 2 years of palbociclib with adjuvant endocrine therapy or endocrine therapy alone.
Approximately 17.6% and 82.1% of patients had stage IIA and stage IIB/III disease, respectively, and the majority (82.5%) received previous chemotherapy. The median follow-up was 31 months, with 516 events of invasive disease–free survival reported; the 3-year invasive disease–free survival rate was similar between with palbociclib and without (89.3% vs. 89.4%).
There were no significant interactions revealed between treatment effect and other factors, including risk category. Additionally, the safety profile of palbociclib was as predicted, with grade 3 or 4 neutropenia being the most common side effect (61.9%). Approximately 42% of individuals discontinued palbociclib before treatment completion, with 28.2% halting therapy due to adverse events. Despite this, there were no observed impacts on survival outcomes, according to the study investigators.
Disclosure: For full disclosures of the study authors, visit sabcs.org.
