Purpose: Accumulating evidence suggests that not all cancer chemotherapy patients who receive first-cycle pegfilgrastim prophylaxis continue to receive it in subsequent cycles and that these patients may be subsequently at higher risk of febrile neutropenia (FN). Additional evidence from US clinical practice is warranted.
Methods: Data from two US private healthcare claims repositories were employed. The source population comprised adults who received "intermediate-risk" or "high-risk" chemotherapy regimens for solid cancers or non-Hodgkin's lymphoma and first-cycle pegfilgrastim prophylaxis. From the source population, all patients who did not receive second-cycle pegfilgrastim prophylaxis ("comparison patients") were matched (1:1) to those who received it ("pegfilgrastim patients") based on cancer, regimen, and propensity score. Odds ratios (OR) for FN-broad and narrow definitions-during the second chemotherapy cycle were estimated for comparison patients versus pegfilgrastim patients using generalized estimating equations.
Results: A total of 2245 comparison patients (5.3 % of source population) were matched to pegfilgrastim patients; cohorts were well-balanced on baseline characteristics. Second-cycle FN incidence proportions for comparison and pegfilgrastim patients were 3.8 versus 2.2 % based on broad definition and 2.6 versus 0.8 % based on narrow definition; corresponding OR were 1.7 (95 % CI 1.2-2.5, p = 0.002) and 3.5 (95 % CI 2.0-6.0, p < 0.001). Results were similar within cancer/regimen-subgroups and were robust when using alternative methods for confounding adjustment.
Conclusions: In this retrospective evaluation of cancer chemotherapy patients who received first-cycle pegfilgrastim prophylaxis in US clinical practice, a clinically relevant minority did not receive second-cycle prophylaxis. Second-cycle FN odds among this subset were significantly higher than they were among those who continued prophylaxis.
Keywords: Febrile neutropenia; Granulocyte colony-stimulating factor; Neulasta; Pegfilgrastim.