Few data about the impact of emotional distress (ED) on treatment efficacy in patients with metastatic breast cancer (mBC) are available.

Aim of this study is to assess the outcomes of patients with mBC receiving first-line treatment according to the presence of baseline ED.

Metastatic breast cancer (mBC) is the most incident and prevalent cancer in the world and, according to a recent meta-analysis, 50% of patients with BC report emotional distress (ED).

In patients with cancer, ED negatively impacts treatment adherence, ability to self-manage the physical and emotional consequences of cancer symptoms and treatment-related adverse events, and overall quality of life. ED has been shown to directly affect treatment outcomes in patients with breast cancer, with studies demonstrating that psychological well-being plays a critical role in therapeutic success.

Furthermore, recent studies showed that baseline ED is associated with a lower efficacy of immunotherapy in patients with non-small cell lung cancer (NSCLC) or melanoma.

Few data about the impact of ED on treatment efficacy in patients with mBC are available. In the first line setting patients receive endocrine therapy, chemotherapy, immunotherapy and/or targeted therapy according to the disease subtype. These agents display different mechanisms of action, which involve the immune system at different levels. However, the role of ED on the efficacy of these treatments according to the BC subtype is unknown.

Aim of this study is to assess the outcomes of patients with mBC receiving first-line treatment according to the presence of baseline ED.

Inclusion Criteria:

• Age over 18 years

• Confirmed histological diagnosis of breast cancer

• No prior treatment for advanced/metastatic cancer

• Indication to receive first-line therapy as per standard clinical practice based on the disease subtype:

  1. cohort A (HR-/HER2-, PD-L1+): pembrolizumab or atezolizumab + chemotherapy
  2. cohort B (HR-/HER2-, PD-L1-): chemotherapy
  3. cohort C (HR+/HER2-): CDK4/6 inhibitor + endocrine therapy
  4. cohort D (HER2+): chemotherapy + trastuzumab and pertuzumab

• Presence of measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) v.1.1 and/or Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST) criteria

• Able to provide full informed consent for the study

Exclusion Criteria:

• Pre-existing severe psychiatric disorders or other conditions that could impair the ability to provide informed consent
• Inability to complete questionnaires
• Presence of another malignancy in the previous 3 years
• Symptomatic brain metastases
• Ongoing treatment with antidepressant and/or anxiolytic drugs

Patients with mBC eligible for standard 1st line treatment