A Study to Assess Treatment Patterns and Treatment Adherence in Early HER2-positive Breast Cancer Participants After Treatment Decentralization

The main purpose of this study is to evaluate the impact of a decentralized treatment model on treatment adherence in participants with early-stage human epidermal growth factor receptor 2- positive (HER2+) breast cancer (BC). This study has 2 groups: Group 1: Consistent Travel Burden (Cohorts A, C, and D), will include participants whose adjuvant therapy location does not increase their travel requirements, and Group 2: Increased Travel Burden (Cohort B), will include participants who must travel from a secondary center to a tertiary center to receive their adjuvant therapy.

Inclusion Criteria: * Diagnosis of stage II and III HER2+ eBC according to European Society For Medical Oncology (ESMO) guidelines * Underwent curative-intent surgical resection for BC * Histologically documented HER2-positive BC (determined per American Society of Clinical Oncology \[ASCO\]/College of American Pathologists \[CAP\] guidelines) before or after surgery Exclusion Criteria: * Any medical or psychiatric condition that, in the investigator's opinion, would compromise the participant's ability to provide informed consent or to complete study-related questionnaires * Receipt of prior neoadjuvant or adjuvant therapy for HER2+ BC at a center other than the 10 participating study sites (Bor, Kladovo, Institute for oncology and Radiology of Serbia (IORS), Loznica, Pančevo, Požarevac, Smederevo, Smederevska Palanka, Šabac, Valjevo) * Participants administratively belonging to the following secondary centers: Bor, Kladovo, Loznica, Pančevo, Požarevac, Smederevo, Smederevska Palanka, Šabac, or Valjevo, who initiated neoadjuvant therapy at IORS instead of their local secondary center