Table 2. Risk of developing grade 3 or 4 neutropenia^a by clinical characteristics in patients receiving palbociclib plus letrozole.

^aNeutropenia was determined based on laboratory tests of absolute neutrophil counts.

^bAbsolute neutrophil count median value = 3.68 × 10³ per mm³.

Abbreviation: ECOG, Eastern Cooperative Oncology Group.