Cost-Effectiveness Analysis of CDK 4/6 Inhibitors

The following model assumptions were made: (a) Patients received ribociclib plus letrozole or, in accordance with National Comprehensive Cancer Network guidelines, palbociclib plus letrozole or letrozole monotherapy; (b) all costs were applied to the mid-cycle occupancy to minimize under-or overestimation; (c) the cost of CDK 4/6 inhibitor therapy was modeled independently of PFS, based on MONALEESA-2 data showing that, on average, patients discontinue treatment before disease progression; (d) MONALEESA-2 and PALOMA-1 were considered equivalent, so that any difference in patient population had a minimal impact on outcomes; (e) subsequent treatment costs accrued at the start of the time horizon; (f) ribociclib plus letrozole and palbociclib plus letrozole were assumed to have had a clinical equivalence effect on OS and PFS, since the therapies share the same CDK 4/6 pathway inhibition mechanism; (g) proportional hazards between comparators held true (in the absence of patient-level data from other trials, it was challenging to reestimate the effect of treatment on a nonproportional hazards scale); (h) AEs occurred in the first month of the model, reflecting the likelihood that they would be experienced within the first year of therapy; and (i) HSUs were dependent on response status, as supported by the published literature.