The efficacy of palbociclib on ER-positive, HER2-negative, advanced breast cancer was investigated in three main studies named PALOMA-1, PALOMA-2, and PALOMA-3.
PALOMA-1 was a randomised, multicentre, open-label trial in postmenopausal women with ER-positive, HER2-negative, advanced (locally advanced or metastatic) breast cancer who had not received previous systemic treatment for advanced disease. The trial enrolled 165 patients randomly allocated to receive either palbociclib (125 mg orally daily for 21 consecutive days, followed by 7 days off treatment) plus letrozole (2.5 mg daily continuously throughout the 28-day cycle) or letrozole alone. The progression-free survival (PFS) was 20.2 months in the palbociclib plus letrozole arm and 10.2 months in the letrozole alone arm. Overall response rate in patients with measurable disease was higher in the palbociclib plus letrozole compared to the letrozole alone arm (55.4% versus 39.4%)3.
PALOMA-2 involved 666 untreated women. They received either palbociclib and letrozole (an aromatase inhibitor) or placebo and letrozole. The median PFS in women taking palbociclib and letrozole was on average 24.8 months (95% CI 22.1, non-estimable)1,8 compared with 14.5 months (95% CI 12.9, 17.1)1,8 for women taking placebo and letrozole5,10.
PALOMA-3 involved 521 women who received either palbociclib and fulvestrant or a placebo and fulvestrant. The median PFS in women taking palbociclib and fulvestrant was 9.5 months (95% CI 9·2–11·0) compared with 4.6 months (95% CI 3·5–5·6) for women taking placebo and fulvestrant9.
In March 2017 the German Institute for Quality and Efficiency in Health Care raised its doubts regarding the added benefit of palbociclib6,7.