Pattern of distant metastasis in molecular subtypes of carcinoma breast: An institutional study

Molecular subtypes of carcinoma breast show a particular pattern of distant metastasis, the knowledge of which can help to diagnose and intervene early in the course of the disease.

The aim of this study was to investigate and establish an association between the molecular subtypes of carcinoma breast and the pattern of distant metastasis.

Single arm, retrospective study.

Totally 400 patients of carcinoma breast (Stage I and II) were selected who were treated between January 2010 and December 2013. All these patients were treated with the standard treatment protocol for breast cancer. The estrogen receptor, progesterone receptor, human epidermal growth factor receptor-2 (HER-2) Neu status, and Ki-67 were done, and patients were classified into luminal A/B, HER-2 enriched, luminal/HER-2, and triple-negative subtypes. All patients were followed up until December 2015, and the pattern of local failure as well as distant metastasis was correlated with the molecular subtypes.

A total of 143 patients developed distant metastasis and local recurrence. Bone was the most common site of metastasis overall. It was the most common type of metastasis in luminal A/B (53.3%) and luminal-HER (57.1%). Brain metastasis was most common in HER-2-enriched subtype (30.3%), whereas liver was the most common site of metastasis in HER-2-enriched subtype (45.45%). The incidence of brain metastasis was comparatively lower in luminal A/B subtype. Local recurrence was most common in HER-2-enriched subtype. The results were statistically significant for lung metastasis and local recurrence (with P = 0.004 and 0.047, respectively).

A strong association exists between the molecular subtypes and the site of distant metastasis in breast cancer which can be used for greater vigilance to detect site-specific distant metastasis beforehand.