Background: Febrile neutropenia (FN) is a serious adverse effect of adjuvant chemotherapy for breast cancer. Primary GCSF prophylaxis is recommended for patients at > 20% risk of FN, but is not funded in Australia with docetaxel (non-anthracycline) regimens in adjuvant breast cancer patients (TC and TCH), despite literature reporting rates of FN of up to 50%. Prophylactic antibiotics can prevent FN, but are not routinely incorporated into chemotherapy guidelines for TC and TCH regimens. This retrospective study evaluates the usage and benefit of primary ciprofloxacin prophylaxis, in patients receiving TC and TCH chemotherapy. Methods: Retrospective review of breast cancer patients receiving adjuvant TC or TCH chemotherapy between 1.1.11 and 30.6.13 (single centre). Logistic regression analysis used to model the contribution of regimen, primary GCSF use (pegfilgrastim), and prophylactic antibiotic use on presence of FN. Results: 131 eligible patients, mean age 55 years (28-77). 96/131 (73%) received TC chemotherapy, 35/131 (27%) received TCH chemotherapy. 97/131 (74%) received primary ciprofloxacin prophylaxis from cycle 1. Primary ciprofloxacin prophylaxis was more frequently prescribed with TC rather than TCH chemotherapy (93% vs 26%). 26 admissions occurred with FN (24 patients). 21/26 admissions for FN occurred after cycle 1 or 2 of chemotherapy. Primary ciprofloxacin prophylaxis significantly reduced the risk of FN (12% vs 41%) and on logistic regression analysis, was the only predictive factor reducing risk of FN (p=0.019). There was no interaction between use of antibiotics and growth factors. Further evaluation of interactions was limited by small numbers. Conclusions: There is a high rate of FN amongst breast cancer patients receiving TC and TCH chemotherapy. Primary ciprofloxacin prophylaxis significantly decreases the risk of FN. Primary ciprofloxacin prophylaxis should be considered for patients receiving TC and TCH chemotherapy, where primary GCSF prophylaxis is unavailable.