Abstract P5-01-09: Improving specificity and refining diagnostic accuracy of MRI in breast cancer with dedicated breast PET (dbPET)

BACKGROUND.

Continued progress in the control of breast cancer will require sustained efforts to provide high-quality screening, diagnosis, and treatment to all segments of the population. MRI has the advantages of providing a 3D view of the breast with high sensitivity, using non-ionizing radiation. However, MRI has significant limitations including its moderate specificity that, in combination with high sensitivity, often leads to unnecessary biopsies. Recently, the MAMmography with Molecular Imaging (MAMMI) dedicated breast PET (dbPET) has emerged as an additional imaging tool for breast cancer diagnosis, clarification of complex lesions and therapy follow-up. It is well known that 18F-FDG-PET has high specificity by assessing metabolic activity, potentially reducing the number of false positive findings. To compare FDG-dbPET with the conventional magnetic resonance imaging (MRI) on breast lesion characterization, we analyzed sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of 37 cases of patients with BC using both dbPET and MRI.

METHODS.

Thirty-seven women with known or suspected breast carcinoma (41 lesions: 36 invasive carcinomas, 2 noninvasive carcinomas, 1 case of ductal hyperplasia, and 2 benign lesions) were enrolled in this study. Both a prone dbPET Mammi scan, and routine breast MRI scans were performed. A joint reading of MRI and PET scans side-by-side by a nuclear medicine physician and a radiologist was performed. Sensitivity and specificity of MRI and dbPET scans were calculated on the basis of post-surgical pathology reports. Breast MRI examinations were performed in a 1.5-T or 3-T commercial imager (Siemens Medical Solutions) with the use of a dedicated breast coil. The imaging sequence included a sagittal T1-weighted localizing sequence followed by a sagittal T2- weighted sequence. A T1-weighted 3D, fat-suppressed fast spoiled-gradient-echo sequence was then performed with an injection of 0.1 mmol per kilogram body weight of gadolinium dimeglumine (Magnevist; Schering). A prone position high-resolution dedicated breast PET was performed 60 min after administration of 90-120 MBq of 18F-FDG.

RESULTS.

A total of 41 lesions were assessed. Lesion size range was 0.2 to 7.6 cm. In lesion-by-lesion analysis, sensitivity and specificity of MRI alone were 91% and 54%, respectively; while lesion-based sensitivity of dbPET was 93% and breast-based specificity was 100%. The positive predictive value and the negative predictive value for MRI alone were 69% and 85%, respectively; and for dbPET were 100% and 89%, respectively. In a significant number of cases, dbPET helped to clarify or disprove positive findings by MRI, and in four cases helped to define new positives that had gone unnoticed at MRI,

CONCLUSION:

Dedicated breast PET scans increase the specificity of MRI. False positives, one of the most challenging aspects of MRI in breast lesions, are reduced. The results of the current study show that FDG-dbPET is more effective than MRI in detecting true breast cancer positives. Its functional information may improve the likelihood of a successful excision, reduce costs from additional procedures, and minimize discomfort and anxiety for the patient.

Citation Format: Ines Dominguez, Michel Herranz, Sze Yiun Teo, Elena Brozos, Carmela Rodriguez, Jasper Chaal, Juan Cueva, Jose Ramon Antúnez, Gabriel Gonzalez Pavón, Marielle Fortier, Rafael López, Alvaro Ruibal. Improving specificity and refining diagnostic accuracy of MRI in breast cancer with dedicated breast PET (dbPET) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-01-09.