Switching to fulvestrant + palbociclib benefits ER + HER2− BC patients with rising bESR1mut

Key clinical point: Switch to fulvestrant + palbociclib from aromatase inhibitor (AI) + palbociclib improved progression-free survival (PFS) without increasing toxicity in patients with estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2−) breast cancer (BC) and high levels of ESR1 mutation in the blood (bESR1^mut).

Major finding: Median PFS improved significantly in the fulvestrant + palbociclib vs AI + palbociclib group (stratified hazard ratio 0.61; 2-sided P = .0040). The rates of most common grade ≥3 adverse events, such as neutropenia (44.3% and 41.7%, respectively) and lymphopenia (4.5% and 3.6%, respectively), were similar in the fulvestrant + palbociclib and AI + palbociclib groups.

Study details: Findings are from the phase 3, PADA-1 trial including 172 patients with ER+HER2− advanced BC, rising bESR1^mut, and no synchronous disease progression with first-line AI + palbociclib who were randomly assigned to continue AI + palbociclib or switch to fulvestrant + palbociclib.

Disclosures: This study was funded by Pfizer. Some authors declared receiving grants, honoraria, consulting fees, or travel support, or having other ties with several sources, including Pfizer.

Source: Bidard FC et al. Switch to fulvestrant and palbociclib versus no switch in advanced breast cancer with rising ESR1 mutation during aromatase inhibitor and palbociclib therapy (PADA-1): A randomised, open-label, multicentre, phase 3 trial. Lancet Oncol. 2022 (Sep 29). Doi: 10.1016/S1470-2045(22)00555-1

Key clinical point: Switch to fulvestrant + palbociclib from aromatase inhibitor (AI) + palbociclib improved progression-free survival (PFS) without increasing toxicity in patients with estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2−) breast cancer (BC) and high levels of ESR1 mutation in the blood (bESR1^mut).

Major finding: Median PFS improved significantly in the fulvestrant + palbociclib vs AI + palbociclib group (stratified hazard ratio 0.61; 2-sided P = .0040). The rates of most common grade ≥3 adverse events, such as neutropenia (44.3% and 41.7%, respectively) and lymphopenia (4.5% and 3.6%, respectively), were similar in the fulvestrant + palbociclib and AI + palbociclib groups.

Study details: Findings are from the phase 3, PADA-1 trial including 172 patients with ER+HER2− advanced BC, rising bESR1^mut, and no synchronous disease progression with first-line AI + palbociclib who were randomly assigned to continue AI + palbociclib or switch to fulvestrant + palbociclib.

Disclosures: This study was funded by Pfizer. Some authors declared receiving grants, honoraria, consulting fees, or travel support, or having other ties with several sources, including Pfizer.

Source: Bidard FC et al. Switch to fulvestrant and palbociclib versus no switch in advanced breast cancer with rising ESR1 mutation during aromatase inhibitor and palbociclib therapy (PADA-1): A randomised, open-label, multicentre, phase 3 trial. Lancet Oncol. 2022 (Sep 29). Doi: 10.1016/S1470-2045(22)00555-1

Key clinical point: Switch to fulvestrant + palbociclib from aromatase inhibitor (AI) + palbociclib improved progression-free survival (PFS) without increasing toxicity in patients with estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2−) breast cancer (BC) and high levels of ESR1 mutation in the blood (bESR1^mut).

Major finding: Median PFS improved significantly in the fulvestrant + palbociclib vs AI + palbociclib group (stratified hazard ratio 0.61; 2-sided P = .0040). The rates of most common grade ≥3 adverse events, such as neutropenia (44.3% and 41.7%, respectively) and lymphopenia (4.5% and 3.6%, respectively), were similar in the fulvestrant + palbociclib and AI + palbociclib groups.

Study details: Findings are from the phase 3, PADA-1 trial including 172 patients with ER+HER2− advanced BC, rising bESR1^mut, and no synchronous disease progression with first-line AI + palbociclib who were randomly assigned to continue AI + palbociclib or switch to fulvestrant + palbociclib.

Disclosures: This study was funded by Pfizer. Some authors declared receiving grants, honoraria, consulting fees, or travel support, or having other ties with several sources, including Pfizer.

Source: Bidard FC et al. Switch to fulvestrant and palbociclib versus no switch in advanced breast cancer with rising ESR1 mutation during aromatase inhibitor and palbociclib therapy (PADA-1): A randomised, open-label, multicentre, phase 3 trial. Lancet Oncol. 2022 (Sep 29). Doi: 10.1016/S1470-2045(22)00555-1