Clinical impact of molecular breast imaging as adjunct diagnostic modality in evaluation of indeterminate breast abnormalities and unresolved diagnostic concerns

Abstract

Purpose: Improvements in molecular breast imaging (MBI) have increased the use of MBI as adjunct diagnostic modality and alternative to MRI. We aimed to assess the value of MBI in patients with equivocal breast lesions on conventional imaging, especially in terms of its ability to rule out malignancy.

Methods: We selected patients who underwent MBI in addition to conventional diagnostics due to equivocal breast lesions between 2012 and 2015. All patients underwent digital mammography, target ultrasound and MBI. MBI was performed using a single-head Dilon 6800 gamma camera after administration of 600 MBq 99m Tc-sestamibi. Imaging was reported according to BI-RADS classification and compared with pathology or follow-up of ≥6 months.

Results: Of 226 women included, pathology was obtained in 106 (47%) and (pre)malignant lesions were found in 25 (11%). Median follow-up was 5.4 years (IQR 3.9-7.1). Sensitivity was higher for MBI compared to conventional diagnostics (84% vs. 32%; P = 0.002), identifying malignancy in 21 and 6 patients, respectively, but specificity did not differ (86% vs. 81%; P = 0.161). Positive and negative predictive value were 43% and 98% for MBI and 17% and 91% for conventional diagnostics. MBI was discordant with conventional diagnostics in 68 (30%) patients and correctly changed diagnosis in 46 (20%) patients, identifying 15 malignant lesions. In subgroups with nipple discharge ( N = 42) and BI-RADS 3 lesions ( N = 113) MBI detected 7 of 8 occult malignancies.

Conclusion: MBI correctly adjusted treatment in 20% of patients with diagnostic concerns after conventional work-up, and could rule out malignancy with a high negative predictive value of 98%.

Fig. 1

Value of adjunct molecular breast imaging in patients with remaining diagnostic concerns after conventional breast imaging. MBI, molecular breast imaging; CD, conventional diagnostic imaging with mammography and ultrasound. BI-RADS ≤ 3 classifications were considered benign and BI-RADS > 3 classifications were considered malignant. BI-RADS scores were compared with histopathological analysis or at least 6 months follow-up imaging.

Fig. 2

Breast imaging of a 56-year-old patient with left-sided breast cancer, detected at 1-year follow-up after treatment for right-sided breast cancer. With digital mammography, more glandular tissue was described in the medial lower quadrant (BI-RADS 3) (a), but no mass could be distinguished and ultrasound was negative. Molecular breast imaging (MBI; Dilon 6800 gamma camera) revealed suspicious sestamibi uptake in the medial lower quadrant over an area of 36 mm (b). MBI-guided biopsy was conducted, showing invasive carcinoma grade 2 with a lobular growth pattern, hormone receptor-positive, HER2-negative.

Fig. 3

Breast imaging of a 69-year-old patient with left-sided breast cancer and ductal carcinoma in situ. The patient was referred by the national breast cancer screening program due to incomplete imaging (BI-RADS 0). There appeared to be slightly more glandular tissue in the medial lower quadrant on digital mammography (a) including the mammographic enlargements (b), with an inhomogeneous echotexture, but no mass could be distinguished. Adjunct molecular breast imaging showed suspicious irregular sestamibi uptake in the medial lower quadrant (c) (Dilon 6800 gamma camera). A hydromarker was placed in the area with inhomogeneous echotexture to confirm correlation with the pathological sestamibi uptake on MBI (d), after which ultrasound-guided biopsy was performed. The representativity of the acquired biopsy specimens was confirmed by showing uptake of sestamibi in the specimens in vitro. Pathological analysis showed ductal carcinoma in-situ grade 3 with a small focus of invasive carcinoma, hormone receptor-negative, HER2-positive. MBI, molecular breast imaging.