Ribociclib boosts PFS in HR+, HER2- breast cancer
The addition of the selective CDK*4/6 inhibitor ribociclib to a regimen consisting of tamoxifen or a non-steroidal aromatase inhibitor (NSAI) and goserelin prolonged progression-free survival (PFS) and generated a higher objective tumour response rate in pre- or perimenopausal women with HR-positive, HER2-negative advanced breast cancer, according to additional results from the MONALEESA-7** trial presented at EBCC 2018.
This multicentre trial comprised 672 participants who were randomized 1:1 to receive ribociclib 600 mg/day (3 weeks on, 1 week off) or placebo in conjunction with tamoxifen 20 mg/day or NSAI (letrozole 2.5 mg/day or anastrozole 1 mg/day) and subcutaneous goserelin 3.6 mg every 28 days. Patients should have previously received up to one prior line of chemotherapy but not endocrine therapy for advanced breast cancer. [EBCC 2018, abstract 1LBA]
Compared with placebo, ribociclib-treated patients had a significantly longer PFS (median, 23.8 vs 13.0 months, hazard ratio [HR], 0.55, 95 percent confidence interval [CI], 0.44–0.69; p=9.83×10–8).
Subgroup analysis comprising patients treated in Europe showed consistent PFS benefit (HR, 0.65, 95 percent CI, 0.44–0.95).
Among participants with measurable disease at baseline, ribociclib-treated participants demonstrated a higher complete or partial response rate than placebo recipients (51 percent vs 36 percent; p=3.17×10–4).
As early as the first tumour evaluation at week 8, a decrease in any tumour size was observed in 58 percent and 48 percent of participants in the ribociclib and placebo arms, respectively.
More ribociclib recipients had a decrease in best percentage change from baseline in any tumour size vs placebo-treated patients (83 percent vs 71 percent).
There was a higher likelihood of a response by 6 months in the ribociclib vs the placebo arm (35 percent vs 25 percent), as well as a longer median duration of response (21.3 vs 17.5 months).
Taken together, these results underscore the early and durable tumour response associated with ribociclib, noted the researchers.
At week 8, mean pain reduction was higher in the ribociclib than the placebo arm (20 percent vs 14 percent), with a median percentage change from baseline of -33 percent and -17 percent, respectively, based on the EORTC QLQ-C30*** pain symptom score.
These findings highlight the role of ribociclib in HR+, HER2- breast cancer and support previous results showing improved PFS when ribociclib was added to letrozole. [N Engl J Med 2016;375:1738-1748]