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Standard-of-care guidelines differ widely from countries with historic access to medical innovation versus those that lack such resources. Metastatic breast cancer (MBC) is one diagnosis that poses a challenge to under-resourced clinicians. The expert panel of ASCO's provide standard-of-care recommendations for resource-constrained countries in three different settings.

Menopausal status and tumor biomarkers should be considered when deciding the ideal treatment. For clinicians practicing in areas with basic resources, defined as vaccination only available to highest-need patients, immunohistochemistry (IHC) staining may not be readily available. Clinicians should assume tumors are HR+ and prescribe tamoxifen.

If HR+ staining can be confirmed via IHC, first-line treatment in resource-rich areas is CDK 4/6 inhibitor and non-steroidal aromatase inhibitor combination therapy. When combination therapy is not available, hormonal therapy should be used. Single-agent chemotherapy and/or surgery can be used in the instance of life-threatening MBC. For triple-negative MBC, clinicians should utilize single-agent chemotherapy when the PD-L1 status cannot be tested, or if the tumor is proven PD-L1 positive and immunotherapy is not accessible.

Premenopausal patients in resource-depleted areas can be treated with ablation and hormone therapy, as well as ovarian suppressing medications. HER2+ tumors can be managed with chemotherapy only, if trastuzumab or pertuzumab are not available. HER2+ MBC, typically treated with trastuzumab deruxtecan, can be treated with trastuzumab emtansine; if trastuzumab emtansine is not available, capecitabine and lapatinib are acceptable replacements. In instances of MBC that is HR+ and HER2+, standard first-line therapy should be used, with endocrine therapy as a second option.

If genetic testing is available and reveals germline BRCA1/2 mutations in the setting of MBC, the first-line therapy is a poly-ADP-ribose polymerase inhibitor, which is not available in resource-scarce countries. Hormone therapy and chemotherapy should be used instead, with hormone therapy appropriate for HR+ tumors and chemotherapy appropriate for HR- tumors.

This study provides valuable guidelines on prescribing information in resource-scarce areas. However, some limitations are present, including a lack of research on how screening for breast cancer occurs in resource-scarce areas and a general lack of data on how cancer is researched in settings with little to no medical resources.

Regardless of these limits, the expert panel in this study provided excellent recommendations for clinicians who find themselves practicing in areas where first-line therapies and diagnostic biomarker testing are not readily available.

Rachel Akers and Ruta Rao, MD, Rush University Medical Center.

Read the guideline here and an interview about it here.