The clinical impacts of molecular subtyping by multigene assay on hormone receptor-positive breast cancers.

BACKGROUND

Multigene assays, such as MammaPrint and BluePrint, provide additional information other than conventional immunohistochemistry (IHC) to help making decision of treatment. This study aims to compare the clinical correlation between molecular subtyping (MS) versus surrogate pathological subtyping (PS).

METHODS

A database from patients receiving MS evaluation in Taipei Veterans General Hospital from 2013 to 2018 was reviewed retrospectively. Patients were categorized as luminal A, luminal B, human epidermal growth factor receptor 2 (HER2) and basal type from MS results and also centrally assessed according to PS (estrogen receptor [ER], progesterone receptor [PgR], HER2, and Ki-67). The clinical correlation between two different subtyping methodologies was analyzed, and the application of chemotherapy was compared.

RESULTS

From 2013 to 2018, a total of 130 patients received MS testing in our institute, and 132 tumor samples were sent for analysis. From MammaPrint, 64 (48.5%) and 55 (41.7%) samples were defined as low and high risks, respectively. The other 13 (9.8%) tumor samples were identified as late recurrence low risk. MS restratified 44 tumors as subtype shifting including 20 tumors from A to B in intrinsic subtypes and 24 tumors from B to A after MS evaluation. Chemotherapy was conducted in only one (1.3%) patient with MS-luminal A but in 87.8% (n = 43) of MS-luminal B subtypes.

CONCLUSION

The MS results restratify the subtypes of hormone receptor positive breast cancer and dominate decision-making of adjuvant therapy. The role of surrogate biomarkers as an alternative tool needs further elucidation. The treatment outcome in different subtypes categorized by MS or PS will be the interesting focus of research.