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

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%.

Molecular Breast Imaging in the Screening Setting

Early detection of breast cancer through screening mammography saves lives. However, the sensitivity of mammography for breast cancer detection is reduced in women with dense breast tissue. Imaging modalities for supplemental breast cancer screening include MRI, whole breast US, contrast-enhanced mammography, and molecular breast imaging (MBI). Molecular breast imaging with 99mTc-sestamibi is a functional imaging test to identify metabolically active areas in the breast with positioning analogous to mammography. Since 2011, there have been six large, published studies of screening MBI as a supplement to mammography involving over 6000 women from four different institutions. A multicenter, prospective clinical trial of 3000 women comparing breast cancer detection using screening digital breast tomosynthesis alone or in combination with MBI recently completed enrollment. This review focuses on the current evidence of MBI use for supplemental breast cancer screening, the strengths and limitations of MBI, and recent technological advances.

Breast-Specific Gamma Imaging with [99mTc]Tc-Sestamibi: An In Vivo Analysis for Early Identification of Breast Cancer Lesions Expressing Bone Biomarkers

The main purpose of this pilot investigation was to evaluate the possible relationship among [⁹⁹mTc]Tc-Sestamibi uptake, the presence of breast osteoblast-like cells, and the expression of molecules involved in bone metabolism, such as estrogen receptor, bone morphogenetic proteins-2, and PTX3. To this end, forty consecutive breast cancer patients who underwent both breast-specific gamma imaging with [^99mTc]Tc-Sestamibi and breast bioptic procedure were retrospectively enrolled. From each diagnostic paraffin block collected in the study, histological diagnosis, immunohistochemical investigations, and energy dispersive X-ray microanalysis were performed. Our data highlight the possible use of breast-specific gamma imaging with [⁹⁹mTc]Tc-Sestamibi for the early detection of breast cancer lesions expressing bone biomarkers in the presence of breast osteoblast-like cells. Specifically, we show a linear association among sestamibi uptake, the presence of breast osteoblast-like cells, and the expression of estrogen receptor, bone morphogenetics proteins-2, and PTX3. Notably, we also observed an increase of [⁹⁹mTc]Tc-Sestamibi in breast cancer lesions with magnesium-substituted hydroxyapatite. In conclusion, in this pilot study we evaluated data from the nuclear medicine unit and anatomic pathology department on breast cancer osteotropism, identifying a new possible interpretation of Breast Specific Gamma Imaging with [⁹⁹mTc]Tc-Sestamibi analysis.

Breast-Specific Gamma Imaging Versus MRI: Comparing the Diagnostic Performance in Assessing Treatment Response After Neoadjuvant Chemotherapy in Patients With Breast Cancer

OBJECTIVE

The purpose of this retrospective study was to evaluate the diagnostic performance of breast-specific gamma imaging (BSGI) and breast MRI in assessing for residual tumor after neoadjuvant chemotherapy (NAC) in patients with breast cancer.

MATERIALS AND METHODS

A total of 114 patients underwent BSGI and MRI for initial staging as well as after undergoing NAC. Of those, 112 underwent subsequent definitive breast surgery. Thirty of the 114 patients had a complete pathologic response to NAC.

RESULTS

BSGI and MRI had comparable sensitivities in detecting residual tumor after NAC (70% vs 83%). BSGI had a higher specificity than MRI in accurately determining complete response after NAC (90% vs 60%).

CONCLUSION

BSGI may be a useful adjunctive tool for predicting a complete pathologic response to NAC.

Correlation of tumor uptake on breast-specific gamma imaging and fluorodeoxyglucose PET/CT with molecular subtypes of breast cancer

Mechanisms of technetium-99m sesta-methoxyisobutylisonitrile (sestamibi) and F-fluorodeoxyglucose (FDG) uptake by tumor are different. The purpose of this study was to investigate the association between the tumor uptake of these 2 tracers in invasive ductal carcinoma and to examine thecorrelation of uptake of each tracer with prognostic factors and tumor molecular subtypes.A total of 96 patients with invasive ductal carcinoma who underwent preoperative breast-specific gamma imaging and FDG positron-emission tomography/computed tomography were retrospectively enrolled. Tumor-to-background ratio (TBR) of sestamibi and maximum standardized uptake value (SUVmax) of FDG were correlated with each other. Each of them was then compared with prognostic factors and molecular subtypes.In all tumors, there was a moderate positive correlation between TBR and SUVmax (r = 0.520, P < .001). Both TBR and SUVmax were significantly correlated with tumor size, incidence of axillary lymph node metastasis, histologic grade, estrogen receptor, progesterone receptor status, and Ki-67.There is a moderate degree of association between TBR of sestamibi and SUVmax of FDG in the invasive breast cancer. Two imaging indexes showed the similar tendency related with prognostic factors and molecular subtypes. While both TBR and SUVmax were significantly different between luminal A and nonluminal A tumors, neither of them had high enough sensitivity or specificity to obviate pathologic and molecular diagnosis.

Gamma Imaging-Guided Minimally Invasive Breast Biopsy: Initial Clinical Experience

OBJECTIVE

The purpose of this study was to evaluate our initial experience with gamma imaging-guided vacuum-assisted breast biopsy in women with abnormal findings.

MATERIALS AND METHODS

A retrospective review of patients undergoing breast-specific gamma imaging (BSGI), also known as molecular breast imaging (MBI), between April 2011 and October 2015 found 117 nonpalpable mammographically and sonographically occult lesions for which gamma imaging-guided biopsies were recommended. Biopsy was performed with a 9-gauge vacuum-assisted device with subsequent placement of a titanium biopsy site marker. Medical records and pathologic findings were evaluated.

RESULTS

Of the 117 biopsies recommended, 104 were successful and 13 were canceled. Of the 104 performed biopsies, 32 (30.8%) had abnormal pathologic findings. Of those 32 biopsies, nine (28.1%) found invasive cancers, six (18.8%) found ductal carcinoma in situ (DCIS), and 17 (53.1%) found high-risk lesions. Of the 17 high-risk lesions, there were three (17.6%) lobular carcinomas in situ, five (29.4%) atypical ductal hyperplasias, two (11.8%) atypical lobular hyperplasias, one (5.9%) flat epithelial atypia, and six (35.3%) papillomas. Two cases of atypical ductal hyperplasia were upgraded to DCIS at surgery. The overall cancer detection rate for gamma imaging-guided biopsy was 16.3%. In this study, gamma imaging-guided biopsy had a positive predictive value of total successful biopsies of 16.3% for cancer and 30.8% for cancer and high-risk lesions.

CONCLUSION

Gamma imaging-guided biopsy is a viable approach to sampling BSGI-MBI-detected lesions without sonographic or mammographic correlate. Our results compare favorably to those reported for MRI-guided biopsy.

Breast-Specific γ-Imaging for the Detection of Mammographically Occult Breast Cancer in Women at Increased Risk

Breast-specific γ-imaging (BSGI) is a physiologic imaging modality that can detect subcentimeter and mammographically occult breast cancer, with a sensitivity and specificity comparable to MRI. The purpose of this study was to determine the incremental increase in breast cancer detection when BSGI is used as an adjunct to mammography in women at increased risk for breast cancer.

METHODS

All patients undergoing BSGI from April 2010 through January 2014 were retrospectively reviewed. Eligible patients were identified as women at increased risk for breast cancer and whose most recent mammogram was benign. Examinations exhibiting focally increased radiotracer uptake were considered positive. Incremental increase in cancer detection was calculated as the percentage of mammographically occult BSGI-detected breast cancer and the number of mammographically occult breast cancers detected per 1,000 women screened.

RESULTS

Included in this study were 849 patients in whom 14 BSGI examinations detected mammographically occult breast cancer. Patients ranged in age from 26 to 83 y, with a mean age of 57 y. Eleven of 14 cancers were detected in women with dense breasts. The addition of BSGI to the annual breast screen of asymptomatic women at increased risk for breast cancer yields 16.5 cancers per 1,000 women screened. When high-risk lesions and cancers were combined, BSGI detected 33.0 high-risk lesions and cancers per 1,000 women screened.

CONCLUSION

BSGI is a reliable adjunct modality to screening mammography that increases breast cancer detection by 1.7% (14/849) in women at increased risk for breast cancer, comparable to results reported for breast MRI. BSGI is beneficial in breast cancer detection in women at increased risk, particularly in those with dense breasts.

Comparative Diagnostic Utility of Low-Dose Breast-Specific Gamma Imaging to Current Clinical Standard

To retrospectively compare low-dose (7-10 mCi) to high-dose (15-30 mCi) breast-specific gamma imaging (BSGI) in the detection of breast cancer. A retrospective review of 223 consecutive women who underwent BSGI exam between February 2011 and August 2013 with subsequent pathologic analysis was performed. Women were divided into low-dose and high-dose groups. The results of BSGI and pathology were compared, and the sensitivity, positive predictive value (PPV), and negative predictive value (NPV) were determined. A subgroup analysis was performed to evaluate specificity using benign follow-up imaging to establish true-negative results. There were 223 women who met inclusion criteria with 109 patients with 153 lesions in the low-dose group and 114 patients with 145 lesions in the high-dose group. Pathologic correlation demonstrates sensitivities of 97.6% (95% CI = 90.9-99.6%) and 94.6% (95% CI = 84.2-98.6%; p = 0.093), PPVs of 62.1% (95% CI = 53.2-70.3%) and 50.5% (95% CI = 40.6-60.3%, p = 0.089), and NPVs of 90.5% (95% CI = 68.2-98.3%) and 92.5% (95% CI = 78.5-98.0%, p = 0.781) in the low-dose and high-dose groups, respectively. Subgroup analysis included 72 patients with 98 lesions in the low-dose group and 116 patients with 132 lesions in the high-dose group, with a specificity of 53.7% (95% CI = 39.7-67.1%) and 66.3% (95% CI = 56.2-75.2%%, p = 0.143), respectively. Low-dose BSGI demonstrated high sensitivity and NPV in the detection of breast cancer comparable to the current standard dose BSGI, with moderate specificity and PPV in a limited subgroup analysis, which was associated with a substantial number of false-positives.

Breast-specific gamma imaging: correlations with mammographic and clinicopathologic characteristics of breast cancer

OBJECTIVE

The purpose of this article is to evaluate the correlations between breast-specific gamma imaging (BSGI) findings and mammographic and clinicopathologic characteristics of breast cancer.

MATERIALS AND METHODS

Our study included 56 breast cancers that had undergone BSGI between August 2010 and December 2012. We reviewed imaging findings (BSGI and mammography) with histopathologic findings, including tumor size, histologic type, nuclear grade, presence of ductal carcinoma in situ (DCIS), and presence of extensive intraductal component (EIC); and immunochemical features, including estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (ERBB2, formerly HER2), Ki67, and p53. We classified cancers into positive or negative groups on the basis of BSGI visibility and investigated the statistical differences in mammographic and histopathologic characteristics between the BSGI-positive and -negative groups.

RESULTS

Among 56 malignancies, 48 (85.7%) were shown to be BSGI positive. Patients in the BSGI-positive group were statistically significantly older than those in the BSGI-negative group (p = 0.027). BSGI-positive cancers were statistically significantly larger than BSGI-negative cancers (p = 0.002). Cancers 1.0 cm or larger, unlike those of subcentimeter size, were statistically significantly more visible on BSGI (p = 0.004). The mammographic findings and mammographic densities did not statistically significantly differ between the BSGI-positive and -negative groups. Invasiveness of cancer showed no statistically significant difference on BSGI finding. Cancers with a DCIS component tended to be BSGI positive, but without statistical significance (p = 0.051). Visibility on BSGI was not statistically significantly associated with EIC, nuclear grade, ER, PR, ERBB2, Ki67, and p53.

CONCLUSION

The sensitivity of BSGI for breast cancer was 85.7%. Breast cancers in older patients, cancers larger than 1.0 cm, and cancers with the DCIS component tended to be visible on BSGI. BSGI was an equally sensitive tool to detect the breast cancer in women with fatty and dense breast.

Breast-specific gamma imaging influences surgical management in patients with breast cancer

Breast-specific gamma imaging (BSGI) is a physiologic breast imaging modality that provides more sensitive detection of breast lesions than mammography or ultrasound, and appears to have greater specificity than breast MRI. The purpose of this study was to evaluate how often BSGI changed surgical management in patients with breast cancer. Charts were reviewed from 218 consecutive eligible patients who had preoperative evaluation with BSGI or MRI before surgery for breast cancer from January 2008 to May 2010. Patients who were initially considered eligible for breast-conserving therapy (BCT) were evaluated to determine how many ultimately had mastectomies. Patients who underwent mastectomy because of personal choice or ineligibility for BCT were excluded. Management was changed to mastectomy in 11.9% of those who had BSGI and 28.9% of those who had MRI. Review of pathology demonstrated that all patients who underwent mastectomies were not candidates for breast conservation. 15.4% of patients who underwent BCT based on BSGI findings required a single re-excision due to positive surgical margins. 14.4% required mastectomy. In the MRI group, 18.8% required a single re-excision, and 6.3% required mastectomy. Evaluation with BSGI changed management to mastectomy in a substantial proportion of patients believed to be eligible for BCT following standard imaging. BSGI is effective in evaluation of extent of disease in patients with breast cancer, and is comparable to MRI in terms of its influence on surgical management.

Contrast-noise-ratio (CNR) analysis and optimisation of breast-specific gamma imaging (BSGI) acquisition protocols

BACKGROUND

Breast cancer is one of the most prevalent forms of cancer in women. Breast-specific gamma imaging (BSGI) is a diagnostic imaging method that uses sestamibi-labelled 99Tc and a dedicated gamma camera to localize malignant lesions in breast tissue. The aim of this study is to investigate if the current acquisition protocol for BSGI at our hospital is optimized for the detection of lesions in our patients.

METHODS

We analyzed patient data and performed a phantom study with a Dilon 6800 gamma camera. The patient data were collected from a group of 13 patients (740 MBq 99mTc-sestamibi, four views per patient were dynamically acquired with a frame duration of 30 s per frame and a total acquisition time of 8 min per view). Reduced-time static images were created, and contrast-to-noise ratios of identified hotspots were determined for different acquisition times. For the phantom study, we used a contrast detail phantom to investigate the contrast and resolution properties, within the range of relevant clinical acquisition parameters. The phantom was filled with a concentration of 80 MBq in 500 ml of water, and we dynamically acquired frames for a total acquisition time of 60 min using a general purpose (GP) collimator. To compare the GP collimator with the high-resolution collimator, a second acquisition was made for both collimators with a total acquisition time of 16 min.

RESULTS

The initial analysis of BSGI scans of the 13 patients showed that a dose reduction by a factor of 3 would not have reduced the number of observable hotspots in each of the acquired views. However, a subsequent systematic analysis of our protocol with a contrast-detail phantom showed that dose reduction results in a lower observability of hotspots, whereas increased doses resulted in a higher observability.

CONCLUSION

We believe that the results of our phantom study are relevant for clinical practice and that further dose reduction cannot be recommended for the BSGI exams at our hospital and that an increase of the administered activity should be considered.