Aims. (Neo)adjuvant breast cancer chemotherapy regimens are associated with relatively high rates of FN. Pegfilgrastim, a GCSF, reduces the risk of FN, hospitalization and infection; however the optimal approach to patient selection for GCSF is unknown. We conducted a retrospective review of patients treated with (neo)adjuvant breast cancer chemotherapy at a single tertiary centre to assess if secondary-GCSF following nadir-neutropenia <1.0x109cells/L was associated with lower rates of FN compared with patients who did not have a nadir blood count in cycle 1 of chemotherapy to direct GCSF use.
Methods. Data were collected from electronic patient records and analysed using Stata. The primary outcome was the FN rate in patients who received secondary-GCSF after cycle 1 nadir-neutropenia, versus the rate that did not have cycle 1 nadir blood counts or secondary GCSF.
Results. Between 11/4/2011-22/4/2018, 584 patients received (neo)adjuvant chemotherapy. The most commonly prescribed regimen was TC (31.9%). Rates of FN were highest in TCH (27.3%) and TC (26.9%). 268 patients (46.1%) received primary and 238 patients (40.8%) received secondary-GCSF. FN in 64 patients and nadir-neutropenia in 124 patients in cycle 1 led to secondary-GCSF. There was no significant difference in rates of FN in patients who received nadir-neutropenia directed secondary-GCSF (6/124, 4.8%, 95% CI 1.1-8.6) compared with those who did not have a nadir measurement (0/50, 0%) (p = 0.1135). Patients >65years were more likely to have FN (20.6% versus 16.6%) and non-FN admissions (32.8% versus 27.4%). 2 of 3 treatment related deaths occurred due to FN.
Conclusions. In this population, nadir blood counts did not contribute to reduced rates of FN or admissions. Observed rates of FN >20% in TC and TCH in routine clinical practice can guide primary GCSF use under existing reimbursement arrangements in Australia.