Real-World Data of Clinicopathological Characteristics and Management of Breast Cancer Patients According to HER2 Status

Change in HER2 expression between initial diagnosis of early BC or locally advanced BC or de novo mBC and any of subsequent BC relapses by IHC and/or ISH validated assays.

HER2 expression changes as assessed by IHC (0+, 1+, 2+, 3+) and/or ISH (positive or negative) validated assays among different lines of treatment in the advanced setting, and/or among different metastatic sites.

Description of all the comprehensive clinicopathological characteristics (age at diagnosis, gender [male or female], baseline Eastern Cooperative Oncology Group [ECOG] performance status [0, 1, or 2], breast cancer pathological subtype at primary site, intrinsic subtype at primary and/or metastatic site by PAM50 test [including luminal A, luminal B, HER2-overexpressing, and basal-like], ER and PgR status [positive and/or negative] at primary and/or metastatic site, HER2 status by IHC and/or ISH testing [HER2-positive, HER2-low expressing, and HER2-negative status per ASCO-CAP guidelines] at primary and/or metastatic site, Ki67 at primary and/or metastatic site, endocrine resistance [primary or secondary]), metastatic sites (bone, brain, visceral involvement) nodal involvement, presence of measurable or evaluable disease per Response Evaluation Criteria In Solid Tumors (RECIST) in all patients enrolled.

Description of disease management and treatment patterns in all patients enrolled for gaining contemporary insights into HER2-low expressing breast cancer treatment trends that may inform clinicians for future management plans.

Identification of patients' genomic profile including DNA alterations and/or RNA expression of genes commonly disrupted in breast cancer, including driver, prognostic-related, and drug-response associated genes in tissue or liquid biopsies from all patients enrolled.

Overall survival (OS) is defined as the time from date of primary treatment initiation to date of death due to any cause. In the absence of confirmation of death, survival time will be censored to last date the participant was known to be alive.

Objective response rate (ORR) is defined as the sum of complete response (CR) and partial response (PR) relative to the number of patients in the analysis set with measurable disease at baseline as per RECIST v.1.1.

Clinical benefit rate (CBR) is defined as the proportion of participants with CR, PR or stable disease (SD) ≥24 weeks relative to the number of patients in the analysis set as per RECIST v.1.1.

Progression-free survival (PFS) is defined as the period of time from treatment initiation to the first occurrence of disease progression or death from any cause, whichever occurs first, as determined locally by the investigator using RECIST v.1.1.

Duration of response (DoR) is defined as the time from the first documentation of objective tumor response (CR or PR) to the first documentation of disease progression, death due to any cause or treatment discontinuation, whichever occurs first as per RECIST v.1.1.