Table 1.
Baseline characteristics in patients with ESR1-mutated tumors and prior ET+CDK4/6i ≥12 months.
| Parameter | Elacestrant (N = 78) | SOC (N = 81) |
|---|---|---|
| Median age, years (range) | 65.5 (40–89) | 63 (32–82) |
| Female, n (%) | 78 (100) | 81 (100) |
| Race or ethnicity, n (%) | ||
| Asian | 3 (3.9) | 3 (3.7) |
| Black or African American | 3 (3.9) | 4 (4.9) |
| Other | 1 (1.3) | 0 |
| White | 59 (75.6) | 59 (72.8) |
| Hispanic or Latino | 6 (7.7) | 7 (8.6) |
| ECOG PS 0, n (%) | 42 (53.9) | 49 (60.5) |
| Metastatic site, n (%) | ||
| Bonea | 67 (85.9) | 69 (85.2) |
| Visceral | 58 (74.4) | 57 (70.4) |
| Liver and/or lungb | 56 (71.8) | 57 (70.3) |
| Number of metastatic sites, n (%)c | ||
| <3 | 42 (53.8) | 40 (49.4) |
| ≥3 | 28 (35.9) | 25 (30.9) |
| Mutations, n (%) | ||
| ESR1d | 78 (100) | 81 (100) |
| D538G | 48 (61.5) | 49 (60.5) |
| Y537S/N | 49 (62.8) | 43 (53.1) |
| PIK3CAe | 27 (34.6) | 35 (43.2) |
| H1047X | 10 (12.8) | 16 (19.8) |
| E542X and E545X | 12 (15.4) | 15 (18.5) |
| TP53 | 32 (41.0) | 29 (35.8) |
| BRCA1/2 | 16 (20.5) | 16 (19.8) |
| HER2-low expressionf | 37 (47.4) | 40 (49.4) |
| Prior adjuvant therapy, n (%) | 44 (56.4) | 47 (58.0) |
| No. of prior lines of ET in the advanced or metastatic setting, n (%) | ||
| 1 | 49 (62.8) | 55 (67.9) |
| 2 | 29 (37.2) | 26 (32.1) |
| No. of prior lines of chemotherapy in the advanced or metastatic setting, n (%) | ||
| 0 | 62 (79.5) | 63 (77.8) |
| 1 | 16 (20.5) | 18 (22.2) |
| Prior CDK4/6i, n (%) | ||
| Abemaciclib | 3 (3.8) | 3 (3.7) |
| Palbociclib | 70 (89.7) | 77 (95.1) |
| Ribociclib | 14 (17.9) | 11 (13.6) |
| Any prior ET, n (%) | 78 (100) | 80 (98.8) |
| Fulvestrant, n (%) | 13 (16.7) | 22 (27.2) |
| AI, n (%) | 72 (92.3) | 71 (87.7) |
| Tamoxifen, n (%) | 7 (9.0) | 7 (8.6) |
| PI3K inhibitor, n (%) | 0 | 0 |
| mTOR inhibitor, n (%) | 5 (6.4) | 1 (1.2) |
Abbreviations: BRCA1/2, breast cancer gene 1 and/or 2; ECOG PS, Eastern Cooperative Oncology Group performance status.
Eighty-five percent of patients had bone and other sites of metastases (30% of these patients had no liver or lung involvement).
Fifty-five percent of patients had liver and other sites of metastases (10% of these patients had no lung or bone involvement); 25% of patients had lung and other sites of metastases (2% of these patients had no liver or bone involvement).
The number of metastatic sites was available for 135 of 159 patients with ESR1-mutated tumors and prior ET+CDK4/6i ≥12 months.
Ninety percent of patients had one or more ESR1 mutations detected in the three hot spots presented (D538G, Y537S, and/or Y537N).
Includes E545K, H1047R, E542K, and others.
Locally assessed HER2 IHC score of 1+ and 2+ with no ISH amplification. Data not available for all patients.