Abstract
AbstractBackground: The objective was to evaluate the potential utility as a prognostic or predictive biomarkers of therapeutic outcome, characterize the incidents, severity, and temporal patterns of blood count abnormalities in routine practice.Methods: A prospective observational study single center study was conducted at medical City Hospital (Baghdad, Iraq) including eighty women (35 to 60 years) with HR + / HER2- advanced breast cancer treated with palbociclib plus letrozole. Baseline characteristics and CBC were collected at baseline and after each cycle (uniformly through 6 cycles). Adverse events were graded by CTC AE v5.0. The primary endpoint was incidence of neutropenia (any grade and grade ≥ 3) over the first six cycles: secondary endpoints where incidence/severity of other cytopenia’s. Analyses were descriptive, repeated measure ANOVA, AUC and ROC.Results: Palbociclib plus letrozole produce frequent hematologic toxicities but they were mostly grade1-2, with low rates of grade 3-4 neutropenia and no febrile events. Higher mean WBC count was significantly associated with non-response and shorter PFS. Higher mean RBC and higher hemoglobin were seen in non-responders which are strongly predicted treatment failure and markedly shorter 6-month PFS.Conclusion: Palbociclib plus letrozole treatment-cycles has no cumulative effect on neutrophils, WBC, RBC or lymphocytes, indicating a stable manageable safety profile. Higher mean WBC and RBC were significantly associated with non-response and shorter PFS. Routine WBC and RBC monitoring may offer a simple low-cost tool to anticipate treatment failure and optimize palbociclib therapy in HR+/HER2- metastatic breast cancer.