Impact of Primary Prophylactic Colony-Stimulating Factor Delivery Method on Febrile Neutropenia: Secondary Analysis of a Pragmatic Cluster Randomized Clinical Trial

Purpose Primary prophylactic colony-stimulating factor (PP-CSF) is recommended for patients receiving chemotherapy with high risk of febrile neutropenia (FN). The impact of PP-CSF delivery method on FN is unknown. We performed a secondary analysis of SWOG S1415CD (Trial Assessing CSF Prescribing Effectiveness and Risk), a pragmatic, cluster-randomized trial evaluating a guideline-informed standing order system to improve PP-CSF use, to evaluate associations between PP-CSF delivery method and FN. Methods Female patients with breast cancer receiving first-line chemotherapy and PP-CSF with a known delivery method (administration in-clinic [IC], home delivery via an on-body device [OBD], or home self-injection [SI]) were included. The primary outcome was FN within 6 months of chemotherapy initiation, defined per the Common Terminology Criteria for Adverse Events. Results Among 1,713 patients, the median age was 55 years (IQR, 46-64). By stage, 566 (33%) were local, 709 (41%) regional, 41 (2%) distant, and 397 (23%) unknown. PP-CSF was delivered IC in 773 (45%), OBD in 862 (50%), and SI in 78 (5%). Most received high-risk FN regimens. Pegfilgrastim use was nearly exclusive in IC and OBD (98% and 99%), versus 29% in SI. FN incidence was low: IC 3.8% (95% CI, 2.5 to 5.3), OBD 5.0% (95% CI, 3.6 to 6.6), and SI 6.4% (95% CI, 2.1 to 14.3; P = .29). FN was associated with high-risk FN regimens (odds ratio [OR], 2.97 [95% CI, 1.2 to 9.9]; P = .04) and Zubrod performance status ≥2 (OR, 4.99 [95% CI, 1.12 to 15.9]; P = .01), but not with delivery method or PP-CSF agent. Conclusion Women with breast cancer receiving chemotherapy and PP-CSF had low rates of FN regardless of PP-CSF delivery method or agent. Delivery decisions may be guided by patient-centered factors including cost, convenience, and access.