Scintimammography for the detection of breast cancer

Breast-Specific Gamma Imaging: An Added Value in the Diagnosis of Breast Cancer, a Systematic Review

Simple Summary

Breast-specific gamma imaging represents an emergent instrument for breast cancer detection. We selected on Medline articles published from 1995 to 2022 that compare various imaging modalities with breast-specific gamma imaging. The aim of this paper was to assess if this imaging method is a more valuable choice in detecting breast malignant lesions compared to morphological counterparts such mammography, ultrasound, and magnetic resonance imaging in terms of specificity, sensibility and positive and negative predictive value. At the cost of a major radiology burden, breast-specific gamma imaging is more specific, with a sensibility comparable to magnetic resonance imaging and higher than ultrasonography and mammography.

Abstract

Purpose: Breast cancer is the most common solid tumor and the second highest cause of death in the United States. Detection and diagnosis of breast tumors includes various imaging modalities, such as mammography (MMG), ultrasound (US), and contrast-enhancement MRI. Breast-specific gamma imaging (BSGI) is an emerging tool, whereas morphological imaging has the disadvantage of a higher absorbed dose. Our aim was to assess if this imaging method is a more valuable choice in detecting breast malignant lesions compared to morphological counterparts. Methods: research on Medline from 1995 to June 2022 was conducted. Studies that compared at least one anatomical imaging modality with BSGI were screened and assessed through QUADAS2 for risk of bias and applicability concerns assessment. Sensitivity, specificity, positive and negative predictive value (PPV and NPV) were reported. Results: A total of 15 studies compared BSGI with MMG, US, and MRI. BSGI sensitivity was similar to MRI, but specificity was higher. Specificity was always higher than MMG and US. BSGI had higher PPV and NPV. When used for the evaluation of a suspected breast lesion, the overall sensitivity was better than the examined overall sensitivity when BSGI was excluded. Risk of bias and applicability concerns domain showed mainly low risk of bias. Conclusion: BSGI is a valuable imaging modality with similar sensitivity to MRI but higher specificity, although at the cost of higher radiation burden.

99mTc-3P4-RGD2 scintimammography in the assessment of breast lesions: comparative study with 99mTc-MIBI

Purpose

To compare the potential application of ^99mTc-3P-Arg-Gly-Asp (^99mTc-3P₄-RGD₂) scintimammography (SMM) and ^99mTc-methoxyisobutylisonitrile (^99mTc-MIBI) SMM for the differentiation of malignant from benign breast lesions.

Method

Thirty-six patients with breast masses on physical examination and/or suspicious mammography results that required fine needle aspiration cytology biopsy (FNAB) were included in the study. ^99mTc-3P₄-RGD₂ and ^99mTc-MIBI SMM were performed with single photon emission computed tomography (SPECT) at 60 min and 20 min respectively after intravenous injection of 738±86 MBq radiotracers on a separate day. Images were evaluated by the tumor to non-tumor localization ratios (T/NT). Receiver operating characteristic (ROC) curve analysis was performed on each radiotracer to calculate the cut-off values of quantitative indices and to compare the diagnostic performance for the ability to differentiate malignant from benign diseases.

Results

The mean T/NT ratio of ^99mTc-3P₄-RGD₂ in malignant lesions was significantly higher than that in benign lesions (3.54±1.51 vs. 1.83±0.98, p<0.001). The sensitivity, specificity, and accuracy of ^99mTc-3P₄-RGD₂ SMM were 89.3%, 90.9% and 89.7%, respectively, with a T/NT cut-off value of 2.40. The mean T/NT ratio of ^99mTc-MIBI in malignant lesions was also significantly higher than that in benign lesions (2.86±0.99 vs. 1.51±0.61, p<0.001). The sensitivity, specificity and accuracy of ^99mTc-MIBI SMM were 87.5%, 72.7% and 82.1%, respectively, with a T/NT cut-off value of 1.45. According to the ROC analysis, the area under the curve for ^99mTc-3P₄-RGD₂ SMM (area = 0.851) was higher than that for ^99mTc-MIBI SMM (area = 0.781), but the statistical difference was not significant.

Conclusion

^99mTc-3P₄-RGD₂ SMM does not provide any significant advantage over the established ^99mTc-MIBI SMM for the detection of primary breast cancer. The T/NT ratio of ^99mTc-3P₄-RGD₂ SMM was significantly higher than that of ^99mTc-MIBI SMM. Both tracers could offer an alternative method for elucidating non-diagnostic mammograms.

Role of Tc99m-Sestamibi scintimammography in assessing response to neoadjuvant chemotherapy in patients with locally advanced breast cancer

INTRODUCTION

Neoadjuvant chemotherapy (NACT) is an essential part of multi-disciplinary management of locally advanced breast cancer (LABC). In this study, we aimed at evaluating the role of Tc99m-Sestamibi scinti-mammography in assessing response to NACT in patients with LABC.

MATERIALS AND METHODS

A total of 42 patients of histologically proven LABC were enrolled in this prospective study. Imaging was performed according to pre-defined protocol at 10 min and 4 h after injection of tracer before the start of chemotherapy, 48 h after start of chemotherapy and at the end of chemotherapy. Quantitative parameters were obtained by calculating the ratio of activity in a region of interest (ROI) drawn over the tumor and the same sized ROI drawn in corresponding location in contra lateral breast.

RESULTS

At the end of chemotherapy, 6 patients achieved complete response, 25 achieved partial response, 11 had stable disease. Various retention indices calculated at baseline, 48 h after first cycle of NACT, and at the end of chemotherapy showed statistically significant difference in responders and non-responders. By using 84.05 as cut-off point for retention index (RI) of tumor calculated 48 h after first cycle of NACT (RI 2) the positive predictive value and negative predictive value, were found to be 41.9% and 72.7% respectively in differentiating responders from non-responders.

CONCLUSION

Early response assessment in patients with LABC to NACT with Tc99m-Sestamibi scintimammography is feasible and if confirmed by further studies can find routine clinical application in differentiating responders from non-responders.

Investigating the limit of detectability of a positron emission mammography device: a phantom study

PURPOSE

A new positron emission mammography (PEM) device (PEM Flex Solo II, Naviscan Inc., San Diego, CA) has recently been introduced and its performance characteristics have been documented. However, no systematic assessment of its limit of detectability has been evaluated. The aim of this work is to investigate the limit of detectability of this new PEM system using a novel, customized breast phantom.

METHODS

Two sets of F-18 infused gelatin breast phantoms of varying thicknesses (2, 4, 6, and 8 cm) were constructed with and without (blank) small, shell-less contrast objects (2 mm thick disks) of varying diameters (3-14.5 mm) [volumes: 0.15-3.3 cc] and activity concentration to background ratio (ACR) (2.7-58). For the phantom set with contrast objects, the disks were placed centrally inside the phantoms and both phantom sets were imaged for a period of 10 min on the PEM device. In addition, scans for the 2 and 6 cm phantoms were repeated at different times (0, 90, and 150 min) post phantom construction to evaluate the impact of total activity concentration (count density) on lesion detectability. Each object from each phantom scan was then segmented and placed randomly in a corresponding blank phantom image. The resulting individual images were presented blindly to seven physician observers (two nuclear medicine and five breast imaging radiologists) and scored in a binary fashion (1-correctly identified object, 0-incorrect). The sensitivity, specificity, and accuracy of lesion detectability were calculated and plots of sensitivity versus ACR and lesion diameters for different phantom thicknesses and count density were generated.

RESULTS

The overall (mean) detection sensitivity across all variables was 0.68 (95% CI: [0.64, 0.72]) with a corresponding specificity of 0.93 [0.87, 0.98], and diagnostic accuracy of 0.72 [0.70, 0.75]. The smallest detectable object varied strongly as a function of ACR, as sensitivity ranged from 0.36 [0.29, 0.44] for the smallest lesion size (3 mm) to 0.80 [0.75, 0.84] for the largest (14.5 mm).

CONCLUSIONS

The detectability performance of this PEM system demonstrated its ability to resolve small objects with low activity concentration ratios which may assist in the identification of early stage breast cancer. The results of this investigation can be used to correlate lesion detectability with tumor size, ACR, count rate, and breast thickness.