Relative Dose Intensity Delivered to Patients with Early Breast Cancer: Canadian Experience

Adjuvant chemotherapy for early breast cancer improves disease-free and overall survival in pre- and postmenopausal women. The importance of maintaining relative dose intensity (rdi) is well-known; however, little information is available from routine clinical practice regarding how well dose intensity is maintained with modern chemotherapy regimens. In a retrospective review of patients undergoing chemotherapy for early breast cancer at a single institution in Canada from January 2006 to November 2007, a total of 263 patients received one of the following regimens: (1) ac-t [doxorubicin (Adriamycin: Pharmacia, Kalamazoo, MI, U.S.A.)–cyclophosphamide, paclitaxel (Taxol: Bristol–Myers Squibb, Princeton, NJ, U.S.A.)]; (2) fec-100 (5-fluorouracil–epirubicin–cyclophosphamide); (3) fec-d (5-fluorouracil–epirubicin–cyclophosphamide, docetaxel). Overall, only 14.4% of patients had a rdi less than 85%. Dose delay or reduction (or both) occurred in 46%, 37%, and 20% of patients receiving fec-100, ac-t, and fec-d respectively. Optimal rdi was delivered to 96%, 95%, and 70.7% of patients for ac-t, fec-d and fec-100 regimens respectively. Patients over 65 years of age accounted for 14% of the total cohort and were more likely to receive a suboptimal rdi than were patients younger than 65 years of age (35% vs. 6.6%). Optimal chemotherapy rdi (>85%) for early breast cancer can be achieved at an academic cancer centre. This goal is less often accomplished in elderly patients, and thus a proactive approach is required for managing toxicity in that population.