Tumour volume doubling time of molecular breast cancer subtypes assessed by serial breast ultrasound.

OBJECTIVES

The aim of our study was to evaluate the tumour volume doubling time (TVDT) of molecular breast cancer subtypes by serial ultrasound (US).

METHODS

Sixty-six patients (mean age, 50 years; range, 29-78 years) with invasive breast cancer underwent initial and follow-up breast US examinations (at least three months apart) with no intervention. TVDT was determined using the tumours' greatest dimensions in two orthogonal planes. The results were compared with clinical, imaging, and tumour variables and molecular subtypes (oestrogen receptor [ER]-positive, human epidermal growth factor receptor 2 [HER2]-positive, and triple negative) using a multiple linear regression analysis.

RESULTS

TVDT exhibited a wide range (46-825 days; median, 141 days) with an overall mean of 193 ± 141 days and mean values of 241 ± 166 days for ER-positive tumours (n = 37), 162 ± 60 days for HER2-positive tumours (n = 12), and 103 ± 43 days for triple-negative tumours (n = 17) (P < 0.0001). In a multivariate regression analysis, compared to other features, only the different molecular breast cancer subtypes showed significant difference in TVDT (P < 0.0001).

CONCLUSIONS

TVDT differed significantly among the three molecular breast cancer subtypes, with the triple-negative tumours showing the fastest growth.

KEY POINTS

Knowledge of tumour volume doubling time provides clues for improving screening. TVDT assessed by serial US differed significantly between breast cancer subtypes. Triple-negative tumours had 2.4-fold shorter TVDT compared to ER-positive tumours. Tumours classified as BI-RADS 3 had shorter TVDT than BI-RADS 4.