Résumé : Purpose: The subcutaneous (SC) administration of trastuzumab is highly preferred by patients. At home, administration of trastuzumab SC might further improve patient benefit. The aims of the BELIS study are to evaluate the safety and tolerability of trastuzumab SC when administered at home by a healthcare professional (HCP) and to evaluate patient-reported outcomes for treatment experience of at home cancer therapy. Methods: This open-label phase IIIb study enrolled HER2-positive early breast cancer patients in Belgium and Israel who completed the first six cycles of trastuzumab IV (neo)adjuvant therapy. The study consisted of three consecutive treatment periods: three cycles of trastuzumab IV and SC each at the hospital and six cycles of trastuzumab SC at home. Results: Between November 2013 and December 2014, 23 centres enrolled 102 patients in the intent-to-treat population of which 101 patients entered the safety population. No new safety signals were detected with as expected, more mild administration site events with trastuzumab SC when compared to IV treatment. All patients agreed that they had benefit from at home administration to a large (18/81; 22%) or very large (63/81; 78%) extent. All HCPs (21/21) agreed that SC is the quickest method from start of preparation to finish of administration and that less resource use is needed. Conclusion: The results of the BELIS study support that trastuzumab SC can be safely administered at home by a HCP and all patients considered this setting as beneficial. HCPs consider the SC formulation as the quickest method to administer trastuzumab. Trial registration: EudraCT Identifier: 2013-000123-13. ClinicalTrials.gov Identifier: NCT01926886.