Indirect Analysis Supports First-Line Ribociclib–Letrozole for HR+HER2- Advanced Breast Cancer

Author: By Lynda Williams, Senior medwireNews Reporter 

medwireNews: First-line ribociclib plus letrozole offers significantly better overall survival (OS) than palbociclib plus letrozole for postmenopausal women with hormone receptor-positive, HER2-negative (HR+HER2-) advanced breast cancer, indicate the findings from a matching adjusted indirect comparison (MAIC) presented at the European Breast Cancer Conference in Barcelona, Spain. 

Using data from the phase III trials MONALEESA-2 and PALOMA-2, the analysis also showed numerically superior progression-free survival (PFS) with the ribociclib combination but the difference between the two regimens did not reach statistical significance. 

Presenting author Komal Jhaveri, from Memorial Sloan Kettering Cancer Center in New York, USA, explained that “MAIC statistically controls for cross-trial differences and provides clinically important comparative results in the absence of head-to-head studies” that “are useful for informing decision making by physicians and policy makers”. 

The investigator noted that the two trials recruited comparable patient populations, and commented that it was “reassuring” that a similar proportion (range 17.7–22.1%) of participants assigned to receive a CDK4/6 inhibitor or placebo in the studies had a treatment-free interval of 12 months or less after the end of (neo)adjuvant treatment. 

Komal Jhaveri said that patients participating in MONALEESA-2 who met criteria for PALOMA-2 were matched to PALOMA-2 participants and reweighting was performed to allow further matching by baseline characteristics, giving an overall effective sample size of 262 patients. 

Baseline characteristics, such as age, race, ECOG performance status, metastases and prior treatment were “nearly identical” in these matched groups of 150 patients given ribociclib in MONALEESA-2 and 112 given palbociclib in PALOMA-2, the presenter emphasised. 

While both the MONALEESA-2 and PALOMA-2 trials had shown a significant OS advantage with use of their respective CDK4/6 inhibitor versus placebo, the MAIC significantly favoured the use of ribociclib plus letrozole with a hazard ratio for death of 0.68 versus palbociclib and letrozole, reported Komal Jhaveri. 

Although the PFS comparison also had a hazard ratio of 0.80 in support of ribociclib, the 95% confidence intervals crossed 1 and the difference was not statistically significant. 

“In light of the ongoing debate [about] whether patient differences could have influenced the comparison of OS data from the MONALEESA-2 and PALOMA-2 trials, the results of this MAIC, which adjusted for patient level differences, provide additional data to support the use of ribociclib plus letrozole over palbociclib plus letrozole as first-line treatment for HR+/HER2- advanced breast cancer”, the presenter concluded. 

Reference  

Jhaveri K, O’Shaughnessy J, Fasching P, et al. Matching adjusted comparison of PFS and OS comparing ribociclib + letrozole vs palbociclib + letrozole as first-line treatment of HR+HER2- ABC: Analysis based on updated PFS & final OS results of MONALEESA-2 & PALOMA-2. Eur J Cancer 2022;175(Supplement 1):S2–S3. DOI: 10.1016/S0959-8049(22)01353-3