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.
Istituto Clinico Humanitas.
Has not received any funding.
All authors have declared no conflicts of interest.