Objective This study was initially designed to evaluate the effect of celecoxib on the regimen of 5-fluorouracil,epirubicin,and cyclophosphamide(FEC)combination,followed by docetaxel(T)in neoadjuvant setting.An unplanned preliminary review on safety was conducted after a halt of the study due to the concerned potential cardiovascular risk of using COX-2 inhibitors.Methods We studied 23 consecutive cases of operable breast cancer having received four cycles of FEC(500 mg/m2,100 mg/m2,500 mg/m2)followed by four cycles of T(100 mg/m2)with concurrent celecoxib(400 mg twice daily)(group A)or same chemotherapy regimen but without concurrent celecoxib(group B).These combined chemotherapies were administered every 3 weeks.The Chi-square test or Fisher’s exact test were used to assess the difference in incidence of limiting hematological toxicites between groups.Results 23 patients(group A:n=12;group B,n=11)received a total of 183 out of 184 planned treatment cycles;one(4%,1/23)of them omitted the fourth cycle of FEC owing to repeated incidences of febrile neutropenia.Received dose intensity(RDI)for FEC in group A(90%±11%)was higher than that in group B(80%±8%)while RDI for T was similar between group A(93%±8%)and group B(96%±9%).Of the first 91 treatment cycles of FEC,limiting hematological toxicity,severe neutropenia including febrile neutropenia,was significantly different between group A and B [(10.4%,5/48)vs.(32.6%,14/43),P=0.009].Other toxicities commonly observed in chemotherapy receiving patients were manageable.Conclusions Neoadjuvant use of FEC followed by T with concurrent celecoxib appeared to be safe for treatment of operable invasive breast cancer.The observed lower incidence of chemotherapy-induced neutropenia is possibly contributed by the administration of COX-inhibitor.We believe that further investigation might provide more evidence on the use of COX-2 inhibitors in breast cancer. Objective This study was initially designed to evaluate the effect of celecoxib on the regimen of 5-fluorouracil, epirubicin, and cyclophosphamide (FEC) combination, followed by docetaxel (T) in neoadjuvant setting. An unplanned preliminary review on safety was conducted after a halt of the study due to the concerned potential cardiovascular risk of using COX-2 inhibitors. Methods We studied 23 consecutive cases of operable breast cancer having received four cycles of FEC (500 mg / m2, 100 mg / m2, 500 mg / m2) by four cycles of T (100 mg / m2) with concurrent celecoxib (400 mg twice daily) (group A) or with concurrent chemotherapy only without celecoxib (group B). The combined chemotherapies were administered every 3 weeks.The Chi-square test or Fisher’s exact test were used to assess the difference in incidence of limiting hematological toxicites between groups. Results 23 patients (group A: n = 12; group B, n = 11) received a total of 183 out of 184 planned treatment cycles; one (4%, 1/23) of them omitted the fourth cycle of FEC due to more incidences of febrile neutropenia. Received dose intensity (RDI) for FEC in group A (90% ± 11%) was higher than that in group B (80% ± 8%) while RDI for T was Of the first 91 treatment cycles of FEC, limiting hematological toxicity, severe neutropenia including febrile neutropenia, was significantly different between groups A and B [93% ± 8%] and group B (96% ± 9% (10.4%, 5/48) vs. (32.6%, 14/43), P = 0.009] .Other toxicities commonly observed in chemotherapy receiving patients were manageable. Conclusions Neoadjuvant use of FEC followed by T with concurrent celecoxib appeared to be safe for treatment of operable invasive breast cancer. observed lower incidence of chemotherapy-induced neutropenia is possibly contributed by the administration of COX-inhibitor. We believe that further investigation might provide more evidence on the use of COX-2 inhibitors in breast cancer.