Table 1.
Baseline patient characteristics
| Patient characteristics | ||||||
|---|---|---|---|---|---|---|
| Cohort 1 (n 34) | Cohort 2 (n 48) | Cohort 3 (n 127) | ||||
| First CDK4/6i exposure | CDK4/6i re-treatment | First CDK4/6i exposure | CDK4/6i re-treatment | First CDK4/6i exposure | CDK4/6i re-treatment | |
| Prognostic markers | ||||||
| Median age | 61 | 62 | 56 | 58 | 61 | 63 |
| Bone only metastasesa | 9 (26%) | 9 (26%) | 18 (37.5%) | 15 (31.2%) | 40 (31.2%) | 23 (18%) |
| Sites of metastatic disease | ||||||
| 1 | 18 (53%) | 18 (53%) | 22 (46%) | 17 (35%) | 49 (39.6%) | 25 (19.7%) |
| 2 | 6 (18%) | 4 (12%) | 11 (23%) | 9 (19%) | 35 (27.6%) | 31 (24.4%) |
| 3 | 6 (18%) | 8 (24%) | 10 (21%) | 12 (25%) | 20 (15.8%) | 29 (22.9%) |
| ≥4 | 4 (12%) | 4 (12%) | 5 (10%) | 10 (21%) | 23 (18.1%) | 42 (33.1%) |
| Brain metastasis | 1 (3%) | 1 (3%) | 3 (6%) | 5 (10%) | 10 (7.9%) | 14 (11%) |
| Prior treatment details | ||||||
| De novo metastatic disease | 11 (32%) | 16 (33%) | 34 (27%) | |||
| Median closest endocrine therapy duration in monthsb | 2.6 (1.3–3.4) | 8.5 (3.6–12.3) | 4.7 (2.4–9.1) | |||
| Median chemotherapy lines prior to retrialb | 0 (0-0) | 0 (0–1) | 1 (0–3) | |||
| Endocrine partner | ||||||
| Aromatase inhibitor | 22 (65%) | 16 (47%) | 44 (92%) | 1 (2%) | 68 (54%) | 14 (11%) |
| SERD | 11 (32%) | 15 (44%) | 1 (2%) | 45 (94%) | 51 (40%) | 78 (61%) |
| Tamoxifen | 0 | 0 | 0 | 1 (2%) | 0 | 1 (0.7%) |
| No endocrine partner | 1 (3%) | 3 (9%) | 3 (6%) | 1 (2%)c | 8 (6%)d | 34 (27%) |
| CDK4/6i | ||||||
| Palbociclib | 28 (82%) | 15 (44%) | 45 (94%) | 45 (94%) | 122 (96.1%) | 4 (3.2%) |
| Abemaciclib | 4 (12%) | 16 (47%) | 3 (6%) | 3 (6%) | 4 (3.2%) | 104 (81.9%) |
| Ribociclib | 2 (6%) | 3 (9%) | 0 | 0 | 1 (0.8%) | 19 (15%) |
| Treatment sequencing | ||||||
| CDK4/6i retrial immediately after initial CDK4/6i failure | 31 (91%) | 41 (85.4%) | 45 (35.4%) | |||
| Median lines of therapy for metastatic diseaseb | 1 (1–3) | 3 (2–4) | 1 (1–2) | 2 (2–4) | 2 (1–4) | 5 (3–7) |
| First line | 19 (56%) | 0 | 29 (60%) | 0 | 43 (33.9%) | 0 |
| Second line | 6 (18%) | 16 (47%) | 7 (15%) | 28 (58%) | 28 (22.1%) | 17 (13.4%) |
| Third line | 1 (3%) | 7 (21%) | 4 (8%) | 6 (13%) | 18 (14.2%) | 23 (18.1%) |
| Fourth and beyond | 8 (24%) | 11 (32%) | 8 (17%) | 14 (29%) | 38 (30%) | 87 (68.5%) |
Baseline clinical characteristics are summarized and separated by respective cohort.
aPatient with bone lesions and breast primary lesion and/or lymph node involvement were included as bone only as far as no presence of visceral disease.
bMedian (Interquartile Range).
cOne patient received bicalutamide as endocrine partner.
dSix patients received bicalutamide as endocrine partner.