Epidemiology and Treatment of HR+/HER2- Breast Cancer in England

Epidemiology and Treatment of HR+/HER2- Breast Cancer in England

The aim of this study was to describe the epidemiology, treatment pathway, treatment access, wastage of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i), and health care resource use among adults with hormone receptor positive, human epidermal growth factor receptor 2 negative (HR+/HER2-) breast cancer (BC) in England, including their treatment pathway leading to progression to metastatic BC for those who were initially diagnosed with early BC. This was a retrospective cohort study using linked registry and administrative data.

Inclusion criteria:

• Patient with a registered diagnosis of International Classification of Diseases,10th Revision (ICD-10) code C50: malignant neoplasm of the breast, between 01 April 2012 and 31 December 2022.
• Patient ≥18 years of age at diagnosis.
• Patient with estrogen receptor-positive (ER+) or progesterone receptor-positive (PR+), i.e., hormone receptor positive (HR+) breast cancer
• Patient with human epidermal growth factor receptor 2 negative (HER2-) breast cancer.

Additional inclusion criteria for patients with metastatic BC were defined as:

• Tumor stage IV at diagnosis or on subsequent treatment or
• Tumor Node Metastases (TNM) staging indicative of M1 at diagnosis or on subsequent treatment or
• Record with ICD-10 codes indicating secondary malignant neoplasm C77* (excluding C771 and C773), C78*, or C79* or
• Initiation of treatment specified for metastatic BC, defined as ribociclib or palbociclib from 01 January 2017 to the end of the study period or abemaciclib from 01 January 2017 to 31 May 2022 or
• Record of treatment for distant/metastatic recurrence.

An additional inclusion criterion for patients with early BC was:

• No evidence of metastatic disease (defined above) before or up to 100 days after the first BC diagnosis date.

Additional inclusion criteria for patients in the NATALEE Trial-aligned sub-cohort:

• Patient with stage IIa BC at diagnosis (i.e., T0-1 N1 or T2 N0 with Grade 3 tumor), or
• Stage IIb BC at diagnosis (i.e., T2 N1, T3 N0), or
• Stage III BC at diagnosis.

Exclusion criteria:

• Patient's sex unknown.

• Patient with ductal carcinoma in situ (DCIS), or lobular carcinoma in situ (LCIS).

• Patient with a diagnosis of Second Edition of the International Classification of Diseases for Oncology (ICD-0-O2) code 0, 1, or 2 denoting non-malignant disease.

• Patient with any indication of co-positive disease before or within 6 months after diagnosis (i.e., HR+ and HER2+) including:

  • treated with trastuzumab
  • treated with tyrosine kinase inhibitors (TKIs)

• Any registered BC tumor or evidence of metastatic cancer prior to index date.