Fixed-dose adjuvant subcutaneous (s.c.) trastuzumab (T) has been approved in the treatment of early HER2-positive breast cancer (BC), based on the evidence of its non-inferiority to standard intravenous (i.v.) infusion. Few data from real-life are available regarding cardiac toxicities associated with fixed-dose subcutaneous T administration. We conducted a retrospective study in order to compare cardiac toxicity profile of adjuvant fixed-dose s.c.-T and weight-based i.v.-T, according to anthropometric data which takes into account more than simply weight.
Patients treated with adjuvant T for HER2-positive breast cancer at Humanitas Research Hospital from December 2013 to October 2017 were evaluated. T was administered at a either fixed dose of 600 mg s.c. or 6 mg/kg i.v, respectively. Data regarding previous chemotherapy, Body Mass Index (BMI), and development of cardiotoxicity (decrease in LVEF >10% points, to a value < 50%) were extracted from medical records. Four BMI classes were considered: underweight (BMI < 18 kg/sqm), normal weight (18-24.9 kg/sqm), overweight (25-29.99), and obesity (≥30). All variables were compared with categorical tests (Pearson Chi-squared with Yates correction or Fisher exact test).
A total of 260 HER2-positive BC patients receiving adjuvant T were analyzed. Median age was 56 (range, 32-88), median BMI 23.5 (range, 15.8-50.2 kg/sqm). 196 (75.38%) patients received s.c.-T and 64 (24.62%) i.v.-T. 156 had a normal weight, while 11 were underweight, 54 overweight and 39 obese. The incidence of cardiotoxicity was not different among the BMI classes according to the route of administration of T (p = 0.28). In the subset of the patients who had developed cardiac toxicity, BMI did not result as a risk factor, as well as a previous treatment with anthracyclines (p = 0.89).
Cardiac toxicity profile of fixed-dose s.c.-T is consistent with that of weight-based i.v.-T in the real-world setting regardless differences in anthropometric data as BMI. Our study confirms safety of subcutaneous T administration, which still represents a valid and more convenient alternative to intravenous administration.
Clinical trial identification
Legal entity responsible for the study
Istituto Clinico Humanitas.
Has not received any funding.
All authors have declared no conflicts of interest.