Antineoplastic Combined Chemotherapy Protocols/therapeutic use; Breast Neoplasms/drug therapy; Carcinoma, Ductal, Breast/drug therapy; Cyclophosphamide/administration & dosage; Doxorubicin/administration & dosage; Pharmacogenetics; ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics; Antineoplastic Combined Chemotherapy Protocols/adverse effects; Aryl Hydrocarbon Hydroxylases/genetics; Biomarkers, Pharmacological/analysis; Biomarkers, Tumor/genetics; Breast Neoplasms/genetics; Breast Neoplasms/mortality; Carcinoma, Ductal, Breast/genetics; Carcinoma, Ductal, Breast/mortality; Cyclophosphamide/adverse effects; Cytochrome P-450 CYP2B6; Doxorubicin/adverse effects; Drug Resistance, Neoplasm/genetics; Drug-Related Side Effects and Adverse Reactions/genetics; Female; Gene Frequency; Genotype; Humans; Middle Aged; Organic Cation Transport Proteins/genetics; Oxidoreductases, N-Demethylating/genetics; Polymorphism, Single Nucleotide; Retrospective Studies; Survival Analysis