Table 1.
Patient characteristics in first-line (1L) and second-line (2L) CDK4/6i cohorts
| Total number of patients | 1L CDK4/6i | 2L CDK4/6i | |
|---|---|---|---|
| 91 | 45 | ||
|
| |||
| Age at start of CDK4/6i (years) | Median (Q1–Q3) | 59 (50–66) | 63 (52–71) |
| Deaths, n (%) | 31 (34.1%) | 27 (60%) | |
| Gender, n (%) | Female | 90 (98.9%) | 43 (95.5%) |
| Male | 1 (1.1%) | 2 (4.5%) | |
| M stage at initial diagnosis, n (%) | M0 | 71 (78.0%) | 28 (62.2%) |
| M1 | 20 (22.0%) | 17 (37.8%) | |
| Sites of metastases at diagnosis | Bone | 75 (82.4%) | 35 (77.8%) |
| Liver | 16 (17.6%) | 9 (20%) | |
| Lung | 28 (30.8%) | 6 (13.3%) | |
| Brain | 3 (3.3%) | 2 (4.4%) | |
| Prior curative intent surgery, n (%) | n = 71 | n = 30 | |
| Lumpectomy | 25 (35.2%) | 14 (46.6%)a | |
| Mastectomy | 46 (64.8%) | 16 (53.4%) | |
| Prior chemotherapy, n (%) | n = 71 | n = 28 | |
| Neoadjuvant chemotherapy | 16 (22.5%) | 5 (17.9%) | |
| Adjuvant chemotherapy | 35 (49.3%) | 17 (60.7%) | |
| None | 30 (42.2%) | 6 (21.4%) | |
| Prior adjuvant radiation therapy, n (%) | None | 24 (33.8%) | 7 (25%) |
| Received | 47 (66.2%) | 21 (75%) | |
| Adjuvant ET, n (%) | None | 7 (9.9%) | 2 (5.9%) |
| Received | 64 (90.1%) | 26 (94.1%) | |
| Median Duration of ET, months (Q1–Q3) | 45 (26–60) | 60 (27.5–60) | |
| Type of ET resistanceb | Primary ET resistance | 9 (14.1%) | 10 (35.7%) |
| Secondary ET resistance | 24 (37.5%) | 10 (35.7%) | |
a
One patient underwent lumpectomy for bone-only metastatic disease after near complete response on ET and another patient underwent mastectomy and found to have metastatic disease shortly after surgery
b
ET resistance was higher in the 2L CDK4/6i cohort due to the majority of patients having previously been on ET as 1L treatment for metastatic breast cancer