Effectiveness of Breast MRI and (18)F-FDG PET/CT for the Preoperative Staging of Invasive Lobular Carcinoma versus Ductal Carcinoma

Purpose

We evaluated the utility of magnetic resonance imaging (MRI) and ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) for the preoperative staging of invasive lobular carcinoma (ILC) of the breast and compared the results with those of invasive ductal carcinoma (IDC).

Methods

The study included pathologically proven 32 ILCs and 73 IDCs. We compared clinical and histopathological characteristics and the diagnostic performances of MRI and ¹⁸F-FDG PET/CT for the primary mass, additional ipsilateral and/or contralateral lesion(s), and axillary lymph node metastasis between the ILC and IDC groups.

Results

Primary ILCs were greater in size, but demonstrated lower maximum standardized uptake values than IDCs. All primary masses were detected on MRI. The detection rate for ILCs (75.0%) was lower than that for IDCs (83.6%) on ¹⁸F-FDG PET/CT, but the difference was not significant. For additional ipsilateral lesion(s), the sensitivities and specificities of MRI were 87.5% and 58.3% for ILC and 100.0% and 66.7% for IDC, respectively; whereas the sensitivities and specificities of ¹⁸F-FDG PET/CT were 0% and 91.7% for ILC and 37.5% and 94.7% for IDC, respectively. The sensitivity of ¹⁸F-FDG PET/CT for ipsilateral lesion(s) was significantly lower in the ILC group than the IDC group. The sensitivity for ipsilateral lesion(s) was significantly higher with MRI; however, specificity was higher with ¹⁸F-FDG PET/CT in both tumor groups. There was no significant difference in the diagnostic performance for additional contralateral lesion(s) or axillary lymph node metastasis on MRI or ¹⁸F-FDG PET/CT for ILC versus IDC.

Conclusion

The MRI and ¹⁸F-FDG PET/CT detection rates for the primary cancer do not differ between the ILC and IDC groups. Although ¹⁸F-FDG PET/CT demonstrates lower sensitivity for primary and additional ipsilateral lesions, it shows higher specificity for additional ipsilateral lesions, and could play a complementary role in the staging of ILC as well as IDC.

Invasive lobular carcinoma of the breast: patient response to systemic endocrine therapy and hormone response in model systems

Invasive lobular carcinoma of the breast (ILC) represents 10-15% of all newly diagnosed breast cancers, affecting ∼30,000 women annually in the United States. However, ILC is critically understudied as a breast cancer subtype. Though the vast majority of ILC are estrogen receptor-positive and present with overall favorable biomarkers, ILC patients do not benefit from improved outcomes versus other breast cancer patients. Patient outcomes, in particular in response to endocrine therapies, are not well understood in ILC, due in large part to the lack of prospective identification in large clinical trials. Further, there is a lack of laboratory models to study cell signaling, hormone response, and endocrine resistance in ILC. In this review, we provide an overview of clinicopathological features of ILC tumors, discuss issues with clinical management, and highlight the disconnect between ILC biomarkers and patient outcomes. We review currently available data on ILC patient outcomes, with a focus on response to endocrine therapy. Additionally, we describe currently available laboratory models for understanding hormone response in ILC cells, and review current data on these model systems. The promise for new insight into ILC, based on extensive representation of the disease in recent large scale genomic studies, is also discussed. Increasing understanding of endocrine response in ILC represents a critical area for future research to improve patient outcomes for this understudied breast cancer subtype.