Abstract PD2-05: Biomarker analysis by baseline circulating tumor DNA alterations in the MONALEESA-3 study

Abstract

Background: In the Phase III MONALEESA-3 (NCT02422615) study, ribociclib (RIB; cyclin-dependent kinase 4/6 inhibitor) + fulvestrant (FUL) significantly prolonged progression-free survival (PFS) vs placebo (PBO) + FUL in postmenopausal women with hormone receptor-positive (HR+), HER2-negative (HER2–) advanced breast cancer (ABC). Here we present MONALEESA-3 efficacy data by molecular alterations detected in circulating tumor DNA (ctDNA) at baseline. Methods: Postmenopausal women (N=726) with HR+, HER2– ABC (treatment naïve or received ≤1 line of prior endocrine therapy for ABC) were randomized 2:1 to RIB or PBO (600 mg/day; 3-weeks-on/1-week-off) + FUL (500 mg per label). Biomarker analysis of baseline ctDNA was an exploratory endpoint. Baseline plasma samples were collected from 692 patients (pts), and plasma ctDNA was analyzed using next-generation sequencing with a targeted panel of ˜550 genes. The subgroup analysis was performed in 600 pts (RIB + FUL n=400; PBO + FUL n=200) with evaluable ctDNA data. Results were not adjusted for multiple testing. Results: Alterations (frequency) were observed in the following genes: PIK3CA (35%), ESR1 (14%), TP53 (18%), CDH1 (12%), FGFR1 (5%), FGFR1/ZNF703/WHSC1L1 (11%), cell cycle-related (CCC) genes (16%), and genes involved in receptor tyrosine kinase (RTK) signaling (20%), and the mitogen-activated protein kinase (MAPK) pathway (10%). PFS hazard ratios favored RIB vs PBO regardless of baseline ctDNA gene alteration status (Table). Events, n/NMedian PFS, months Gene(s)RIB + FULPBO + FULRIB + FULPBO + FULHazard ratio; 95% confidence intervalPIK3CAWT108/26570/12422.3416.490.67; 0.49–0.91Altered75/13549/7616.3611.100.75; 0.52–1.08ESR1WT141/33899/17622.3414.880.66; 0.51–0.85Altered42/6220/249.236.110.71; 0.41–1.23TP53WT132/32598/17022.3414.880.62; 0.47–0.80Altered51/7521/309.177.390.75; 0.44–1.27CDH1WT156/35697/17320.6316.490.70; 0.54–0.90Altered27/4422/2712.095.130.46; 0.24–0.86FGFR1WT165/378113/19221.3214.550.65; 0.51–0.83Altered18/226/88.346.110.64; 0.23–1.75FGFR1/ZNF703/WHSC1L1WT155/356105/18121.3214.650.67; 0.52–0.85Altered28/4414/1910.976.670.73; 0.37–1.43CCCWT138/331103/17422.0814.650.61; 0.47–0.79Altered45/6916/2612.659.130.92; 0.51–1.65RTKWT126/31595/16622.3414.820.61; 0.47–0.80Altered57/8524/349.175.780.82; 0.50–1.35MAPKWT158/357105/18320.0414.820.69; 0.54–0.89Altered25/4314/1714.723.610.47; 0.22–1.00 Numerically shorter PFS was observed in pts with altered vs wildtype (WT) genes, irrespective of treatment. A slight trend towards limited RIB benefit vs PBO was observed in pts with altered CCC and RTK genes. RIB benefit was more pronounced vs PBO in pts with altered CDH1 and MAPK genes. PIK3CA and ESR1 analyses for pts receiving treatment in the first- or second-line setting will be presented at the meeting. Conclusions: Generally consistent PFS benefit for RIB + FUL vs PBO + FUL was observed irrespective of baseline ctDNA alterations; altered status trended to correlate with a shorter PFS. Results are hypothesis generating and should be interpreted with caution for some subgroups due to small sample sizes. Citation Format: Neven P, Petrakova K, Val Bianchi G, De la Cruz-Merino L, Jerusalem G, Sonke GS, Nusch A, Beck JT, Chia S, Solovieff N, Rodriguez Lorenc K, Miller M, Su F, Lm S-A. Biomarker analysis by baseline circulating tumor DNA alterations in the MONALEESA-3 study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD2-05.

Mechanisms of Resistance to CDK4/6 Inhibitors: Potential Implications and Biomarkers for Clinical Practice

“…Contrastingly, PIK3CA mutations were detected in the circulating DNA of 129 patients enrolled in PALOMA-3, with no significant association observed with response to treatment (9). Similarly, biomarker analysis of MONALEESA-3 demonstrated consistent benefit from ribociclib plus fulvestrant, irrespective of PIK3CA alteration status, as detected in baseline circulating tumor DNA (35). Functioning downstream of PI3K is 3-phosphoinositide-dependent protein kinase 1 (PDK1), a vital requisite for the full activation of AKT (36).…”

Phase I/II Trial of Exemestane, Ribociclib, and Everolimus in Women with HR+/HER2− Advanced Breast Cancer after Progression on CDK4/6 Inhibitors (TRINITI-1)

“…In these analyses, treatment with fulvestrant (including in combination with a CDK4/6i) showed potential efficacy benefit in patients with ESR1-mutated tumors. [36][37][38] Fulvestrant, rather than EXE (which was used in TRINITI-1), may be a more suitable option for these patients; however, it is unknown whether continuation of a CDK4/6i in combination with fulvestrant and EVE would be the optimal treatment. Consistent with the results of TRINITI-1, PIK3CA was the most common mutation in BOLERO-2 and the median PFS was shorter in patients with mutated PIK3CA.…”

Liquid Biopsy: New Tool to Overcome CDKi Resistance Mechanism in Luminal Metastatic Breast Cancer

“…This polytherapy improved PFS regardless of ctDNA genetic alterations at baseline: PIK3CA, TP53, CDH1, FGFR1, cell cycle-related genes or genes involved in receptor tyrosine kinase signalling [54]. However, Neven et al found shorter PFS was correlated with altered gene status irrespective of treatment (polytherapy or letrozole alone) [54], [55].…”