Purpose: Common breast cancer chemotherapy regimens are associated with a risk of febrile neutropenia, so prophylactic colony-stimulating factors are incorporated for high-risk patients. Filgrastim utilizes weight-based dosing; however, its sustained-release formulation utilizes fixed dosing. The purpose of this study is to determine whether obese breast cancer patients who receive pegfilgrastim are at increased risk of developing febrile neutropenia.
Methods: This study is a single-center, retrospective chart review. Breast cancer patients were categorized as normal weight (body mass index < 30), overweight (body mass index 30-39), or obese (body mass index ≥ 40).
Results: A total of 442 eligible patients were identified between 1 July 2012 and 19 May 2016. Twenty-eight were included in the obese group. Twenty-eight patients from each non-obese group were randomly selected to make up the overweight and normal weight groups. Incidence of febrile neutropenia was 1, 2, and 2 of 28 in the normal weight, overweight, and obese research groups, respectively. Increased use of antibiotics was observed in the obese group as compared to the normal and overweight groups (2, 1, 1, respectively; p = 0.0005). Median number of days on antibiotics was statistically significantly higher in the obese group at 10 days compared to the normal and overweight groups at seven days ( p = 0.03).
Conclusion: Obese patients are not at increased risk of febrile neutropenia. However, they may have a lower threshold for febrile neutropenia and require more antibiotics after chemotherapy. Clinical significance of these results cannot be determined given the small sample size, so further multicenter studies are required.
Keywords: Breast cancer; febrile neutropenia; obesity; pegfilgrastim.