Table 2.
Studies assessing the role of CDK4/6 inhibition after progression on CDK4/6 inhibition in metastatic breast cancer.
| MAINTAIN [9] | PACE [8,37] | PALMIRA [10] | |
|---|---|---|---|
| Phase | II | II | II |
| Sample size | 120 | 220 | 198 |
| Design | Fulvestrant or exemestane ± ribociclib in patients with HR+, HER2- BC whose cancer previously progressed on CDK 4/6 inhibitor + ET (1:1) | Arm A (n = 55): fulvestrant Arm B (n = 111): fulvestrant and palbociclib; or Arm C (n = 54): fulvestrant, palbociclib, and avelumab in patients with HR+, HER2- BC whose cancer previously progressed on any CDK 4/6 inhibitor + AI | Fulvestrant or letrozole ± palbociclib in patients with HR+, HER2- BC whose cancer previously progressed on palbociclib inhibitor + ET (2:1) |
| Initial CDK 4/6 inhibitor | Palbociclib (84%), ribociclib (11%) | Palbociclib (90%) | Palbociclib (100%) |
| Continuation CDK 4/6 inhibitor | Ribociclib (100%) | Palbociclib (100%) | Palbociclib (100%) |
| Continuation ET | Fulvestrant (83%), exemestane (17%) | Fulvestrant (100%) | Fulvestrant (90%), letrozole (10%) |
| PFS ET + CDK4/6 inhibitor vs. ET | 5.3 vs. 2.8 months (HR 0.56) | 4.6 vs. 4.8 months (HR 1.11) | 4.9 vs. 3.6 months (HR 0.84) |
Abbreviations: AI: aromatase inhibitor; CDK: cyclin dependent kinase; ER: endocrine therapy; HER2: human epidermal growth factor receptor 2; HR: hazard ratio; HR + hormone receptor positive; PFS: progression free survival * The primary objective was to evaluate PSF between arms A and B.