Triple-negative invasive breast cancer (TNBC): Mammographic, US, and MR imaging features according to androgen receptor (AR) expression.

Abstract

159 Background: A subset of TNBC is characterized by an androgen gene signature and early clinical trials have demonstrated clinical benefit with the use of the AR antagonist, bicalutamide, for the treatment of patients with AR+, estrogen receptor/progesterone receptor- breast cancer. Methods: AR expression was assessed immunohistochemically in 125 patients (median age; 54 years, range; 26-82 years) with TNBC from a consecutive series of 1,086 operable invasive breast cancers. Two experienced breast imaging radiologists (6 and 24 years of experience, respectively) reviewed the mammograms, US, and MR images without knowledge of clinicopathologic findings. The imaging and pathologic features of 33 AR-positive TNBCs were compared with those of 92 AR-negative TNBCs by using the Fisher’s exact or chi-squared tests. Results: AR expression in TNBC is significantly associated with mammographic findings (P < 0.001), lesion type at MR imaging (P < 0.001), and mass shape or margin at ultrasound (P < 0.001; P= 0.002). The highest PPVs for AR-positive cancer were non-mass enhancement on MR imaging (PPV, 1.00; 95% CI: 0.61, 1.00), calcifications only seen on mammography (PPV, 1.00; 95% CI: 0.37, 1.00), and spiculated masses on US (PPV, 1.00; 95% CI: 0.22, 1.00). Conclusions: AR-positive and AR-negative tumors have distinct imaging features in TNBC. The presence of calcifications or focal asymmetries at mammography, the presence of echogenic halo or non-complex hypoechoic masses at US, masses with irregular shape or indistinct margins at mammography and US, and masses with irregular shape or spiculated margins, or non-mass lesions at MR imaging were associated with AR expression in TNBC. These imaging features may be used to predict AR status, which could assist in treatment planning, prediction of response, and assessment of prognosis for patients with TNBC.