The role of 99mTc-sestamibi and other conventional radiopharmaceuticals in breast cancer diagnosis

Enhancement of Anti-Tumoral Properties of Paclitaxel Nano-Crystals by Conjugation of Folic Acid to Pluronic F127: Formulation Optimization, In Vitro and In Vivo Study

A brand-new nano-crystal (NC) version of the hydrophobic drug Paclitaxel (PT) were formulated for cancer treatment. A stable NC formulation for the administration of PT was created using the triblock co-polymer Pluronic F127. To achieve maximum entrapment effectiveness and minimal particle size, the formulation was improved using the central composite design by considering agitation speed and vacuum pressure at five levels (coded as +1.414, +1, 0, -1, and -1.414). According to the Design Expert software's predictions, 13 runs were created and evaluated for the chosen responses. The formulation prepared with an agitation speed of 1260 RPM and a vacuum pressure of 77.53 mbar can meet the requirements of the ideal formulation in order to achieve 142.56 nm of PS and 75.18% EE, according to the level of desirability (D = 0.959). Folic acid was conjugated to Pluronic F127 to create folate receptor-targeted NC. The drug release profile of the nano-crystals in vitro demonstrated sustained release over an extended period. Folate receptor (FR)-targeted NC (O-PT-NC-Folate) has also been prepared by conjugating folic acid to Pluronic F127. MTT test is used to validate the targeting efficacy on the FR-positive human oral cancer cell line (KB). At pharmacologically relevant concentrations, the PT nano-crystal formulation did not cause hemolysis. Compared to non-targeted NC of PT, the O-PT-NC-Folate showed a comparable but more sustained anti-cancer effect, according to an in vivo anti-tumor investigation in NCI/ADR-RES cell lines. The remarkable anti-tumor effectiveness, minimal toxicity, and simplicity of scale-up manufacturing of the NC formulations indicate their potential for clinical development. Other hydrophobic medications that are formulated into nano-systems for improved therapy may benefit from the formulation approach.

Molecular Breast Imaging-guided Percutaneous Biopsy of Breast Lesions: A New Frontier on Breast Intervention

Molecular breast imaging (MBI) is an increasingly recognized nuclear medicine imaging modality to detect breast lesions suspicious for malignancy. Recent advances have allowed the development of tissue sampling of MBI-detected lesions using a single-headed camera (breast-specific gamma imaging system) or a dual-headed camera system (MBI system). In this article, we will review current indications of MBI, differences of the two single- and dual-headed camera systems, the appropriate selection of biopsy equipment, billing considerations, and radiation safety. It will also include practical considerations and guidance on how to integrate MBI and MBI-guided biopsy in the current breast imaging workflow.

A brief overview of metal complexes as nuclear imaging agents

Metallic radionuclides have been instrumental in the field of nuclear imaging for over half a century. While recent years have played witness to a dramatic rise in the use of radiometals as labels for chelator-bearing biomolecules, imaging agents based solely on coordination compounds of radiometals have long played a critical role in the discipline as well. In this work, we seek to provide a brief overview of metal complex-based radiopharmaceuticals for positron emission tomography (PET) and single photon emission computed tomography (SPECT). More specifically, we have focused on imaging agents in which the metal complex itself rather than a pendant biomolecule or targeting moiety is responsible for the in vivo behavior of the tracer. This family of compounds contains metal complexes based on an array of different nuclides as well as probes that have been used for the imaging of a variety of pathologies, including infection, inflammation, cancer, and heart disease. Indeed, two of the defining traits of transition metal complexes-modularity and redox chemistry-have both been creatively leveraged in the development of imaging agents. In light of our audience, particular attention is paid to structure and mechanism, though clinical data is addressed as well. Ultimately, it is our hope that this review will not only educate readers about some of the seminal work performed in this space over the last 30 years but also spur renewed interest in the creation of radiopharmaceuticals based on small metal complexes.

Dedicated Breast Gamma Camera Imaging and Breast PET: Current Status and Future Directions

Recent advances in nuclear medicine instrumentation have led to the emergence of improved molecular imaging techniques to image breast cancer: dedicated gamma cameras using γ-emitting ^99mTc-sestamibi and breast-specific PET cameras using ¹⁸F-fluorodeoxyglucose. This article focuses on the current role of such approaches in the clinical setting including diagnosis, assessing local extent of disease, monitoring response to therapy, and, for gamma camera imaging, possible supplemental screening in women with dense breasts. Barriers to clinical adoption and technologies and radiotracers under development are also discussed.

Molecular breast imaging: an emerging modality for breast cancer screening

Screening mammography is recognized as an imperfect imaging tool that performs poorly in women with dense breast tissue - a limitation which has driven demand for supplemental screening techniques. One potential supplemental technique is molecular breast imaging (MBI). Significant improvements in gamma camera technology allow MBI to be performed at low radiation doses, comparable with those of tomosynthesis and mammography. A recent screening trial in women with dense breast tissue yielded a cancer detection rate of 3.2 per 1000 for mammography alone and 12.0 per 1000 for the combination of mammography and MBI. MBI also demonstrated a lower recall rate than that of mammography. MBI is a promising supplemental screening technique in women with dense breast tissue.

Dense breasts: a review of reporting legislation and available supplemental screening options

OBJECTIVE

The objectives of this article are to discuss the Mammography Quality Standards Act (MQSA) and what it means for patients, define breast density and explain how it is measured, review the new state-based legislation regarding the reporting of dense breast tissue directly to patients and the possibility of an adjunct screening examination, describe possible supplemental screening options and the advantages and disadvantages of each, and outline the current shortcomings and unanswered questions regarding new legislation.

CONCLUSION

Breast density is now established as an independent risk factor for developing breast cancer irrespective of other known risk factors. Women with breast density in the upper quartile have an associated four to five times greater risk of developing breast cancer relative to women with breast density in the lower quartile. Many states have enacted or proposed legislation requiring mammographers to report to patients directly if they have dense breast tissue and recommend discussing the possibility of a supplemental screening examination with their physicians. However, there is currently no consensus as to whether a supplemental screening examination should be pursued or which modality to use. Possible supplemental screening modalities include ultrasound, MRI, digital breast tomosynthesis, and molecular breast imaging. The U.S. Food and Drug Administration recently approved an automated breast ultrasound system for screening whole-breast ultrasound in patients with dense breasts. However, many questions are still unanswered including the impact on morbidity and mortality, cost-effectiveness, and insurance coverage.

Radionuclide methods and instrumentation for breast cancer detection and diagnosis

Breast cancer mammography is a well-acknowledged technique for patient screening due to its high sensitivity. However, in addition to its low specificity the sensitivity of mammography is limited when imaging patients with dense breasts. Radionuclide imaging techniques, such as coincidence photon-based positron emission tomography and single photon emission computed tomography or scintimammography, can play a role in assisting screening of such patients. Radionuclide techniques can also be useful in assessing treatment response of patients with breast cancer to therapy, and staging of patients to diagnose the disease extent. However, the performance of these imaging modalities is generally limited because of the poor spatial resolution and sensitivity of the commercially available multipurpose imaging systems. Here, we describe some of the dedicated imaging systems (positron emission mammography [PEM] and breast-specific gamma imaging [BSGI]) that have been developed both commercially and in research laboratories for radionuclide imaging of breast cancer. Clinical studies with dedicated PEM scanners show improved sensitivity to detecting cancer in patients when using PEM in conjunction with additional imaging modalities, such as magnetic resonance imaging or mammography or both, as well as improved disease staging that can have an effect on surgical planning. High-resolution BSGI systems are more widely available commercially and several clinical studies have shown very high sensitivity and specificity in detecting cancer in high-risk patients. Further development of dedicated PEM and BSGI systems is ongoing, promising further expansion of radionuclide imaging techniques in the realm of breast cancer detection and treatment.

Scintimammography for the detection of breast cancer

Scintimammography is a functional imaging technique whereby radionuclide tracers in the patient's breasts are observed with a radiation-detection camera (gamma-camera). Tracers are designed to accumulate in tumors more than in healthy tissue; the most common tracers used to date are Tc-99m sestamibi and Tc-99m tetrofosmin. Scintimammography is useful in some clinical indications as an adjunct to mammography and to reduce the rates of negative biopsies, and it is recommended for lesions where additional information is required to reach a definitive diagnosis. Patients with equivocal mammograms may benefit from this test, as well as women with dense breasts and those with implants, since scintigraphy is not affected by breast density and the photons arising from the radiotracer are not overly attenuated by implants. Scintimammography is also of value in patients with locally advanced breast cancer, for monitoring and predicting the response to neoadjuvant chemotherapy. The near availability of high-resolution breast-dedicated cameras will allow the suboptimal sensitivity in detecting cancers of less than 1 cm to be improved; this is currently the main limitation of scintimammography. These new devices also have the potential to increase the number of breast scintigraphies performed and the role of nuclear medicine in breast cancer imaging.

Nuclear imaging of the breast: translating achievements in instrumentation into clinical use

Approaches to imaging the breast with nuclear medicine and∕or molecular imaging methods have been under investigation since the late 1980s when a technique called scintimammography was first introduced. This review charts the progress of nuclear imaging of the breast over the last 20 years, covering the development of newer techniques such as breast specific gamma imaging, molecular breast imaging, and positron emission mammography. Key issues critical to the adoption of these technologies in the clinical environment are discussed, including the current status of clinical studies, the efforts at reducing the radiation dose from procedures associated with these technologies, and the relevant radiopharmaceuticals that are available or under development. The necessary steps required to move these technologies from bench to bedside are also discussed.

99mTc-thymine scintigraphy may be a promising method in the diagnosis of breast cancer

OBJECTIVE

Mammography has been established as the gold standard for the detection of breast cancer, and imaging techniques such as ultrasonography, magnetic resonance imaging, scintigraphy and positron emission tomography may be useful to improve its sensitivity and specificity. The objective of this study with breast scintigraphy was to evaluate the uptake of 99mTc-thymine in mammary lesions.

METHODS

A total of 45 patients were included in this study. Thirty-three patients (73%) were subjected to surgery or percutaneous biopsy, providing histopathological data. The other 12 patients who remained under surveillance received clinical examinations and biannual mammography with a normal follow-up of at least three years, the data from which were used for comparison with the scintimammography results.

RESULTS

The majority of patients (64.4%) had clinically impalpable lesions with a mammogram diagnosis of microcalcifications, impalpable nodules, or focal asymmetry. Of the studied lesions, 87% were smaller or equal to 20 mm in diameter, and 22% had malignant histopathological findings. Scintigraphy with 99mTc-thymine had a sensitivity of 70%, a specificity of 85.7%, positive and negative predictive values of 58.3% and 90.9%, respectively, and an accuracy of 82.2%.

CONCLUSIONS

The results of this study are consistent with those previously reported by other authors. The good specificity and high negative predictive value of this technique and the absence of uptake in the heart indicate that it may be a promising complementary method in clinical practice and that it may contribute to reducing unnecessary benign biopsies.

Radiotracer breast cancer imaging: Beyond FDG and MIBI

Radiotracer imaging with MIBI and FDG have shown the benefit of the functional imaging of breast cancer. Newer radiopharmaceuticals targeted to particular aspects of breast cancer biology will likely play an important role in directing more specific and individualized breast cancer treatment. Future studies will need to test the ability of SPECT and PET imaging to detect breast cancer, but also to assess target expression, identify resistance factors, and measure early response to treatment. This will require protocols designed to test the predictive capability of imaging in the setting of a therapy trial, a new paradigm for breast cancer imaging, for which radiotracer imaging is ideally suited.

[Non-invasive imaging modalities for preoperative axillary lymph node staging in patients with breast cancer]

In the last decade sentinel lymph node biopsy has become a well-established method for axillary lymph node staging in patients with breast cancer. Using preoperative imaging modalities it can be tested whether patients are suitable for sentinel node biopsy or if they should directly undergo an axillary dissection. The imaging modalities used must be mainly characterized by a high positive predictive value (PPV). For this question B-mode ultrasound is the best evaluated method and provides clear morphological signs for a high PPV (>90%) but the sensitivity barely exceeds 50%. It has not yet been proven whether other modalities such as duplex sonography, magnetic resonance imaging, computed tomography (CT) or scintigraphy might achieve a higher sensitivity while still maintaining a high PPV. There is only some evidence that positron emission tomography (PET) might achieve a higher sensitivity. This should be confirmed by further studies because PET or PET/CT will play an increasing role for an initial whole body staging in patients with breast cancer in the near future.

Evaluation of morphine effect on tumour angiogenesis in mouse breast tumour model, EATC

Breast cancer is the leading cause of death among women, and morphine is used to relieve the pain of patients with cancer. The data on the effects of morphine on tumour growth and angiogenesis are contradictory. We determined in mouse breast cancer model whether analgesic doses of morphine would affect tumour angiogenesis, and then the correlation between microvessel density (MVD), Doppler sonography (DS) and 99mTc-Tetrofosmin (TF) uptake. Ehrlich ascites tumour cell xenografts, Pgp-negative tumour were divided into two groups: (a) Morphine sulphate [0.714 mg/kg/day (equivalent to 50 mg per day for a 70 kg human)], (b) no-morphine. For the determination of angiogenesis in mice tumour tissue, TF scintigraphy, microvessel density and DS were done. MVD was significantly different between groups (49.4±1.8 vs. 41.8±1.9, morphine and no-morphine groups, respectively, P<0.001). A strong correlation was found between late uptakes of mass at scintigraphy and degree of angiogenesis in histopathologic examination (r=0.52, P<0.01). There was statistically significant inverse correlation between degree of angiogenesis in histopathologic examination and washout ratio of TF (r=0.40, P<0.05). The higher values for angiogenesis are related to higher TF reuptake. There was no statistically significant correlation between DS and TF. A strong correlation was found between MVD and grade of DS (r=0.51, P<0.01). Our preclinical mice study indicates that morphine at clinically relevant doses stimulates angiogenesis, and angiogenesis triggered of morphine is demonstrated with MVD and DS, but not TF. However, uptake and washout of TF are compared with immunohistochemically assessed morphine-stimulated angiogenesis in tumour tissue.

Observer detection limits for a dedicated SPECT breast imaging system

An observer-based contrast-detail study is performed in an effort to evaluate the limits of object detectability using a dedicated CZT-based breast SPECT imaging system under various imaging conditions. A custom geometric contrast-resolution phantom was developed that can be used for both positive ('hot') and negative contrasts ('cold'). The 3 cm long fillable tubes are arranged in six sectors having equal inner diameters ranging from 1 mm to 6 mm with plastic wall thicknesses of <0.25 mm, on a pitch of twice their inner diameters. Scans of the activity filled tubes using simple circular trajectories are obtained in a 215 mL uniform water filled cylinder, varying the rod:background concentration ratios from 10:1 to 1:10 simulating a large range of biological uptake ratios. The rod phantom is then placed inside a non-uniformly shaped 500 mL breast phantom and scans are again acquired using both simple and complex 3D trajectories for similarly varying contrasts. Summed slice and contiguous multi-slice images are evaluated by five independent readers, identifying the smallest distinguishable rod for each concentration and experimental setup. Linear and quadratic regression is used to compare the resulting contrast-detail curves. Results indicate that in a moderately low-noise 500 mL background, using the SPECT camera having 2.5 mm intrinsic pixels, the mean detectable rod was approximately 3.4 mm at a 10:1 ratio, degrading to approximately 5.2 mm with the 2.5:1 concentration ratio. The smallest object detail was observed using a 45 degrees tilted trajectory acquisition. The complex 3D projected sine wave acquisition, however, had the most consistent combined intra- and inter-observer results, making it potentially the best imaging approach for consistent results.

Accuracy of (99m)Tc-sestamibi scintimammography for breast cancer diagnosis

Scintimammography using (99m)Tc-sestamibi is a noninvasive and painless diagnostic imaging method that is used to detect breast cancer when mammography is inconclusive. Because of the advantages of labeling with (99m)Tc-sestamibi and its high efficiency in detecting carcinomas, it is the most widespread agent for this purpose. Its accumulation in the tumor has multifactorial causes and does not depend on the presence of architectural distortion or local or diffuse density variation in the breast. The objective of this study was to evaluate the accuracy of scintimammography for detecting breast cancer. One hundred and fifty-seven patients presenting 158 palpable and non-palpable breast nodules were evaluated. Three patients were male and 154 were female, aged between 14 and 81 years. All patients underwent scintimammography, and the nodule was subjected to cytological or histological study, i.e., the gold standard for diagnosing cancer. One hundred and eleven malignant and 47 benign nodules were detected, with predominance of ductal carcinomas (n=94) and fibroadenoma/fibrocystic condition (n=11/n=11), respectively. The mean size was 3.11 cm (7-10 cm) among the malignant nodules and 2.07 cm among the benign nodules (0.5-10 cm). The sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 89, 89, 95, 78 and 89%, respectively. Analysis on the histological types showed that the technique was more effective on tumors that were more aggressive, such as ductal carcinoma. In this study, (99m)Tc-sestamibi scintimammography was shown to be an important tool for diagnosing breast cancer when mammography was inconclusive.

Molecular breast imaging

Molecular breast imaging (MBI) is a new nuclear medicine technique that utilizes small semiconductor-based gamma-cameras in a mammographic configuration to provide high-resolution functional images of the breast. Current studies with MBI have used Tc-99m sestamibi, which is an approved agent for breast imaging. The procedure is relatively simple to perform. Imaging can be performed within 5 min postinjection, with the breast lightly compressed between the two detectors. Images of each breast are acquired in the craniocaudal and mediolateral oblique projections facilitating comparison with mammography. Key studies have confirmed that MBI has a high sensitivity for the detection of small breast lesions. In patients with suspected breast cancer, MBI has an overall sensitivity of 90%, with a sensitivity of 82% for lesions less than 10 mm in size. Sensitivity was lowest for tumors less than 5 mm in size. Tumor detection does not appear to be dependent on tumor type, but rather on tumor size. Studies using MBI and breast-specific gamma-imaging have shown that these methods have comparable sensitivity to breast MRI. A large clinical trial compared MBI with screening mammography in over 1000 women with mammographically dense breast tissue and increased risk of breast cancer and showed that MBI detected two-to three-times more cancers than mammography. In addition, MBI appears to have slightly better specificity than mammography in this trial. MBI provides high-resolution functional images of the breast and its potential applications range from evaluation of the extent of disease to a role as an adjunct screening technique in certain high-risk populations. MBI is highly complementary to existing anatomical techniques, such as mammography, tomosynthesis and ultrasound.

Molecular breast imaging: use of a dual-head dedicated gamma camera to detect small breast tumors

OBJECTIVE

Molecular breast imaging with a single-head cadmium zinc telluride (CZT) gamma camera has previously been shown to have good sensitivity for the detection of small lesions. To further improve sensitivity, we developed a dual-head molecular breast imaging system using two CZT detectors to simultaneously acquire opposing breast views and reduce lesion-to-detector distance. We determined the incremental gain in sensitivity of molecular breast imaging with dual detectors.

SUBJECTS AND METHODS

Patients with BI-RADS category 4 or 5 lesions < 2 cm that were identified on mammography or sonography and scheduled for biopsy underwent molecular breast imaging as follows: After injection of 740 MBq of technetium-99m ((99m)Tc) sestamibi, 10-minute craniocaudal and mediolateral oblique views of each breast were acquired. Blinded reviews were performed using images from both detectors 1 and 2 and images from detector 1 only (simulating a single-head system). Lesions were scored on a scale of 1-5; 2 or higher was considered positive.

RESULTS

Of the 150 patients in the study, 128 cancers were confirmed in 88 patients. Averaging the results from the three blinded readers, the sensitivity of dual-head molecular breast imaging was 90% (115/128), whereas the sensitivity from review of only single-head molecular breast imaging was 80% (102/128). The sensitivity for the detection of cancers < or = 10 mm in diameter was 82% (50/61) for dual-head molecular breast imaging and 68% (41/61) for single-head molecular breast imaging. On average, 13 additional cancers were seen on dual-head images and the tumor uptake score increased by 1 or more in 60% of the identified tumors.

CONCLUSION

Gains in sensitivity with the dual-head system molecular breast imaging are partially due to increased confidence in lesion detection. Molecular breast imaging can reliably detect breast lesions < 2 cm and dual-head molecular breast imaging can significantly increase sensitivity for subcentimeter lesions.

New diagnostic techniques for breast cancer detection

Breast imaging has made huge advances in the last decade, and along with newer techniques to diagnose primary breast cancer, many novel methods are being used and look promising in detecting distant metastasis, recurrent disease and assessing response to treatment. Full-field digital mammography optimizes the lesion–background contrast and gives better sensitivity, and it is possible to see through the dense tissues by altering computer windows; this may be particularly useful in younger women with dense breasts. The need for repeat imaging is reduced, with the added advantage of reduced radiation dose to patients. Computer-aided detection systems may help the radiologist in interpretation of both conventional and digital mammograms. MRI has a role in screening women at high risk for breast cancer. It also aids in cancer management by assessing response to treatment and can help in deciding appropriate surgery by providing accurate information on the extent of the tumor. Newer diagnostic techniques such as sestamibi scans, optical imaging and molecular diagnostic techniques look promising, but need more investigation into their use. Their roles will appear clearer in coming years, and they may prove to be of help in further investigating lesions that are indeterminate on standard imaging. Other upcoming techniques are contrast-enhanced mammography and tomosynthesis. These may give additional information in indeterminate lesions, and when used in screening they aid in reducing recall rates, as shown in recent studies. PET/computed tomography has a role in detecting local disease recurrence and distant metastasis in breast cancer patients.

Evaluation of different counting methods for use in radiochemical purity testing procedures for 99mTc-labelled radiopharmaceuticals

The efficiency and accuracy of different methods for quality control of radiopharmaceutical preparations for diagnostic purpose were studied. The radiochemical purity of (99m)Tc Tetrafosmin, (99m)Tc Exametazime, (99m)Tc Sestamibi and (99m)Tc Oxidronate was evaluated by different thin layer chromatography systems, followed by cutting of the strips into two or three sections and by the measurement of radioactivity distribution by dose calibrator or gamma counter. In addition, to confirm the accuracy of these routine procedures, the strips were cut into a number of micro-sections (14-25) and each of them evaluated by the gamma counter. The three tested procedures gave similar results and revealed a good and comparable accuracy. The radioactivity measurement with the dose calibrator remains the most practicable because of the rapidity of execution.

Radioguided Intraoperative Margins Evaluation (RIME): Preliminary results of a new technique to aid breast cancer resection

AIMS

Women undergoing breast-conserving surgery for cancer can present residual disease. We have developed a technique called Radioguided Intraoperative Margins Evaluation (RIME) that uses a radiopharmaceutical to distinguish normal and cancer tissues. The aim of this study was to assess whether RIME is a feasible technique, and if it could help in breast cancer resection with free margins, minimizing residual disease.

METHODS

Twenty-three breast cancer patients programmed for mastectomy were selected. Before surgery, the patients were submitted to scintimammography with 99mTc-sestamibi to estimate the optimal time to begin radioguided surgery. Twenty patients were submitted to magnetic resonance imaging (MRI), to evaluate skin, deep fascia and to detect other tumor foci. At the beginning of the surgery, the same dose of 99mTc-sestamibi was intravenously injected into patients. Tumor resection was performed under guidance of a gamma-probe, characterizing the RIME technique. Finally, modified radical mastectomy was performed. Tumor and residual breast were histopathologically examined.

RESULTS

The RIME technique was successfully performed in all patients. The principal tumor was removed by this technique and provided 82.6% of histologically free margins (mean margins, 4.8 mm). Additionally, 47.8% of patients were without residual disease. The mean size of residual carcinoma was 3.67 mm and generally located near the tumor bed (<1.5 cm). There was no significant association between presence of residual disease and tumor size or margin status.

CONCLUSION

RIME is a feasible technique that could help tumor resection with free margins; however, it seems to be limited for small carcinoma foci.

Fusion of Magnetic Resonance and Scintimammography Images for Breast Cancer Evaluation: A Pilot Study

BACKGROUND

To achieve a more specific method to estimate the real size of breast cancer, we have developed a method to fuse magnetic resonance imaging (MRI) and scintimammography (SM) images. The aim of this study was to assess the feasibility of this method and to evaluate its accuracy to measure the size of breast cancer compared with MRI alone, mammography, and clinical examination, employing pathologic size as the gold standard.

METHODS

Twenty consecutive breast cancer women at stages IIA-IIIA, scheduled for mastectomies, underwent SM with (99m)Tc-sestamibi and MRI with gadolinium 2-10 days before surgery. All patients had had recent mammographies and were examined clinically. Software was developed in visual language to perform the fusion between MRI and SM images and tumor measurements (MRI/SM). The tumor size, in 3 diameters (anteroposterior, longitudinal, and transverse), for each examination was correlated with pathological measurements using linear regression.

RESULTS

The MRI/SM technique was successfully performed in all patients, and the principal tumor was measured by this method. The MRI/SM cancer measurements correlated better with pathology than MRI, mammography, and clinical exam in all diameters analyzed (r = 0.88, 0.81, 0.81; SE = 0.11, 0.14, 0.11 in anteroposterior, longitudinal, and transverse diameters, respectively).

CONCLUSIONS

The MRI/SM is a feasible technique and appears to be more accurate than other examinations (MRI alone, mammography, and clinical exam) to measure breast cancer size.

Molecular breast imaging: advantages and limitations of a scintimammographic technique in patients with small breast tumors

Preliminary studies from our laboratory showed that molecular breast imaging (MBI) can reliably detect tumors <2 cm in diameter. This study extends our work to a larger patient population and examines the technical factors that influence the ability of MBI to detect small breast tumors. Following injection of 740 MBq Tc-99m sestamibi, MBI was performed on 100 patients scheduled for biopsy of a lesion suspicious for malignancy that measured <2 cm on mammography or sonography. Using a small field of view gamma camera, patients were imaged in the standard mammographic views using light pain-free compression. Subjective discomfort, breast thickness, the amount of breast tissue in the detector field of view, and breast counts per unit area were measured and recorded. Follow-up was obtained in 99 patients; 53 patients had 67 malignant tumors confirmed at surgery. Of these, 57 of 67 were detected by MBI (sensitivity 85%). Sensitivity was 29%, 86%, and 97% for tumors <5, 6-10, and > or =11 mm in diameter, respectively. In seven patients, MBI identified eight additional mammographically occult tumors. Of 47 patients with no evidence of cancer at biopsy or surgery, there were 36 true negative and 11 false positive scans on MBI. MBI has potential for the regular detection of malignant breast tumors less than 2 cm in diameter. Work in progress to optimize the imaging parameters and technique may further improve sensitivity and specificity.

Radioguided Surgery Using Intravenous 99mTc Sestamibi Associated with Breast Magnetic Resonance Imaging for Guidance of Breast Cancer Resection

The purpose of this study was to evaluate the feasibility of surgery radioguided with intravenous (99m)Tc sestamibi associated with magnetic resonance imaging (MRI) of the breast to detect tumor extent and guide complete tumor resection. A descriptive experimental study was developed with 10 breast cancer patients (stage IIA-IIB) who underwent mastectomy. From 2 to 10 days before surgery, the patients underwent breast MRI with 0.1 mmol/kg of gadolinium and scintimammography with a 740 MBq of (99m)Tc sestamibi. A region of interest was drawn around the tumor image and an uptake curve as a function of time was plotted to calculate the optimal time to perform radioguided surgery. In the perioperative period, the same dose of (99m)Tc sestamibi was intravenously injected into the patients. Tumor resection was performed under the guidance of a gamma probe. MRI was used to evaluate the skin and deep fascia involvement and to detect occult tumor foci which were also excised. Subsequently a modified radical mastectomy was performed. Tumor and residual breast were histopathologically examined. In a series of 10 women, all demonstrated (99m)Tc sestamibi uptake in tumor cells. Eight patients showed no disease in the residual breast, one presented with one foci of invasive ductal carcinoma measuring 0.5 cm in diameter located 5 cm from the tumor bed, and one presented with one foci of ductal carcinoma in situ measuring 0.8 cm at the resection margin. The mean tumor size in the histopathologic assessment was 3.3 cm and in MRI was 5.0 cm. Radioguided surgery using (99m)Tc sestamibi associated with MRI is a feasible technique that can be employed in tumor resection.

Relationship between prognostic factors of breast cancer and 99mTc-sestamibi uptake in patients who underwent scintimammography: Multivariate analysis of causes of false-negative results

The complementary role of sestamibi scintimammography (SSM) in patients with breast cancer (BC) is well established. The aim of this study was to establish whether a relationship exists between sestamibi uptake, evaluated as a tumour-to-background ratio (TBR), and the main prognostic factors of BC. SSM with the measurement of TBR was performed preoperatively in 102 women (median age 57 years, range 32-81 years) who underwent curative surgery for primary BC. Final pathology showed 4 (3.9%) with pT1a, 17 (16.7%) with pT1b, 44 (43.1%) with pT1c and 37 (36.3%) with pT2 breast carcinomas. The overall sensitivity of SSM was 80.4%. An ANOVA showed significant (P<0.01) differences between the TBR of patients with G1 vs. G3 tumours, and between the TBR of those with G2 vs. G3 breast carcinomas. Moreover, there was a difference (P=0.021) between the TBR of patients (n=12, 11.8%) with CEA serum levels >10 ng/ml (2.031+/-0.420), and those with normal (n=90, 88.2%) CEA values (1.713+/-0.446), whilst no difference (P=NS) was found between patients (n=27, 26.5%) with CA 15-3 >30 U/ml (1.893+/-0.401) and those with normal (n=75, 73.5%) CA 15-3 values (1.699+/-0.462). There was a mild inverse correlation between TBR and both the oestrogen (R=0.25, P=0.011) and the progesterone receptor (R=0.23, P=0.02) rate. The logistic regression analysis showed that only size and CA 15-3 serum levels represent true independent parameters, but the function was able to predict only 11 out of 21 (52.4%) patients with false-negative SSM. TBR is independent of age and mainly correlates with the size of the tumour. There are no reliable preoperative prognostic factors that are really useful for improving SSM sensitivity in patients with small breast carcinomas.

Comparison of small field of view gamma camera systems for scintimammography

OBJECTIVE

To compare the performance characteristics of three compact gamma camera systems for scintimammography.

METHODS

A multi-crystal NaI system (Dilon 6800), a multicrystal CsI system (Digirad 2020tc Imager) and a prototype cadmium zinc telluride (CZT) detector were evaluated using a breast phantom with simulated tumours of 1.8-9.8 mm in diameter and a tumour to background ratio of 5.6 : 1. A conventional Anger-based gamma camera was also evaluated for comparative purposes.

RESULTS

The conventional gamma camera had the highest intrinsic sensitivity of the four systems and utilized the highest resolution collimator. However, the prototype CZT and the CsI systems yielded the best spatial resolution over the range 0-5 cm from the collimator face and better visualized small (5-7 mm) tumours.

CONCLUSION

In addition to the advantage of close proximity to the breast, two of the three compact detectors offered superior performance to a conventional gamma camera for scintimammography.

Correlation between 99mTc-MIBI uptake and angiogenesis in MIBI-positive breast lesions

This study was undertaken to assess the correlation between the degree of accumulation and the washout of 99m technetium methoxyisobutylisonitrile ((99m)Tc-MIBI) and angiogenesis in MIBI-positive breast lesions. Twenty-eight patients (mean age, 51+/-11 years) with 31 breast lesions who underwent scintimammography were studied. Anterior, left and right prone lateral images were obtained 20 min and 3 h after the injection of 740 MBq (99m)Tc-MIBI. All breast lesions showed increased (99m)Tc-MIBI uptake. Early and delayed tumor to background activity ratios (T/BG) and washout index (early tumor uptake-delayed tumor uptake divided by early tumor uptake) were calculated. Vascular endothelium was immunohistochemically labeled using a biotinylated monoclonal antibody directed against the factor-VIII-associated antigen using standard biotin-avidin technique. Angiogenesis was evaluated by assessing the vascular surface density (VSD) and the microvessel number (NVES) within 10 randomly chosen areas. All pathological data were compared with early and delayed T/BG activity ratios and washout index of (99m)Tc-MIBI. Statistical analysis was performed using Spearman correlation test. There was no statistically significant correlation between the degree of angiogenesis and early T/BG (r = .287, P > .05 with VSD, r = .351, P > .05 with NVES), delayed T/BG (r = .277, P > .05 with VSD, r = .315, P > .05 with NVES) and the washout index (r = .268, P > .05 with VSD, r = .285, P > .05 with NVES) of (99m)Tc-MIBI in all breast lesions. There was no statistically significant correlation between the degree of angiogenesis and early T/BG (r = .235, P > .05 with VSD, r = .356, P > .05 with NVES), delayed T/BG (r = .181, P > .05 with VSD, r = .285, P > .05 with NVES) and the washout index (r = .158, P > .05 with VSD, r = .187, P > .05 with NVES) of (99m)Tc-MIBI in 24 invasive breast lesions. No statistically significant correlation was found between the degree of angiogenesis and early T/BG (r = -.036, P > .05 with VSD, r = -.107, P > .05 with NVES), delayed T/BG (r = -.500, P > .05 with VSD, r = -.429, P > .05 with NVES), but there was a high correlation between angiogenesis and the washout index (r = .893, P < .05 with VSD, r = .964, P < .05 with NVES) of (99m)Tc-MIBI in seven noninvasive breast lesions. Amount of (99m)Tc-MIBI uptake in breast lesions is dependent on several factors. Our study indicates that early and delayed (99m)Tc-MIBI uptakes in MIBI-positive breast lesions are not related to angiogenesis in both invasive and noninvasive breast lesions. But washout index of (99m)Tc-MIBI in noninvasive breast lesions is highly correlated with angiogenesis. (99m)Tc-MIBI scintigraphy does not seem to be able to indicate angiogenic property of invasive breast lesions.

Clinical utility of 99mTc-Sestamibi scintimammography in the management of equivocal breast lesions

The aim of this study was to assess the utility of 99mTc-sestamibi scintimammography (SM) in patients with suspected primary or recurrent breast cancer. Forty-four (44) breast lesions (17 with suspected recurrence of disease) in 40 patients were included into the study. In these patients, the results of conventional diagnostic methods were equivocal or inconclusive. Twenty-one (21) lesions were palpable and 23 lesions were not. Histological examinations performed during the follow-up revealed malignancy in 24 specimens. SM correctly identified 21 of them, as well as 12 true negatives. There were 8 false-positive studies; therefore, the sensitivity of SM was 87.5%, specificity was 60%, positive predictive value (PPV) was 72.4%, and the negative predictive value (NPV) was 80%. The sensitivity in palpable lesions was 100%; three (3) false negatives, 1 recurrence, and 2 cancers, all of them nonpalpable. In conclusion, SM is useful in equivocal palpable lesions for resolving diagnostic uncertainty after conventional examination, and can limit the number of surgical interventions for benign disease. However, its use in nonpalpable tumors is not recommended.

Clinical applications of 99mTc-sestamibi scintimammography

Mammography is the imaging modality of choice in detection of early, nonpalpable breast cancer. However, scintimammography may prove to be a very useful adjunct to a nondiagnostic or difficult mammography. Future prospective studies will have to be designed so that the specific clinical applications of scintimammography will be well defined. To be clinically relevant, each niche where scintimammography is potentially indicated should be clearly evaluated and incorporated into an algorithm of investigation of breast cancer, taking into consideration the relative advantages and limitations of scintimammography. Special care to obtain high-quality scintimammographic studies is mandatory. Because poor quality studies may be the major drawback, the nuclear medicine community should remind the lesson learned from radiologic mammography. Furthermore, it is also hoped that significant improvement in the scintigraphic equipment and data acquisition will be seen in a very near future to have more widespread clinical diagnostic applications of scintimammography.

Molecular breast imaging: a new technique using technetium Tc 99m scintimammography to detect small tumors of the breast

OBJECTIVE

To determine the sensitivity of molecular breast imaging (MBI) to detect small cancers of the breast.

PATIENTS AND METHODS

A cadmium-zinc-telluride gamma camera with a field of view of 20 x 20 cm was used. The detector elements were 2.5 x 2.5 mm. The gamma camera was mounted on a modified mammographic gantry. Between November 2001 and March 2004, we performed MBI on patients who were scheduled to undergo biopsy for a lesion suggestive of malignancy that was smaller than 2 cm on a mammogram. Patients were injected with 20 mCi of technetium Tc 99m sestamibi and underwent imaging immediately after injection. Using light pain-free compression, we obtained craniocaudal and mediolateral oblique views of each breast.

RESULTS

Of the 40 women included in the study, 26 had a total of 36 malignant lesions confirmed at surgery. Of these 36 lesions, 33 were detected by MBI (overall sensitivity, 92%). Of the 22 malignant lesions 1 cm or smaller in diameter, 19 were detected by MBI (sensitivity, 86%). Two patients had false-negative MBI results. Of the 14 malignant lesions larger than 1 cm in diameter, all were identified correctly by MBI. In 4 patients, MBI identified additional lesions not seen on mammography that were confirmed subsequently on magnetic resonance imaging and were true-positive cases at surgery. Three of these patients had lesions in the breast contralateral to the breast containing the initial mammographic finding suggestive of malignancy. Of 14 patients with no evidence of cancer at biopsy or surgery, 9 had true-negative (normal) scans and 5 had false-positive scans on MBI. False-positive results included benign fibroadenoma (2 patients), inflammatory fat necrosis (1 patient), benign breast parenchyma (1 patient), and complex sclerosing lesion (1 patient).

CONCLUSION

This prototype gamma camera system for MBI reliably detects malignant breast lesions smaller than 2 cm. Furthermore, we obtained the highest sensitivity (86%) yet reported for the detection of lesions smaller than 1 cm. These results suggest an important role for MBI, particularly for women in whom the sensitivity of mammography is reduced by the density of the breast parenchyma.

Single-photon agents for tumor imaging:201TI,99mTc-MIBI, and99mTc-tetrofosmin

This review aims at fostering comprehension and knowledge not only for expert physicians who can skillfully handle various techniques for tumor imaging but also for young practitioners in the field of nuclear medicine. As image processing software and hardware become smaller, faster and better, SPECT will adapt and incorporate these advances. A principal advantage of SPECT over PET is the more widespread availability of the equipment and lower cost for the introduction of the system in community-based facilities. Moreover, SPECT has become less dependent on a limited number of acknowledged experts for its interpretation owing to a variety of handy computer tools for imaging analyses. The increasing use of PET in tumor imaging is not necessarily proportional to the decline of SPECT. General physicians' attention to SPECT technology would also increase more by evoking their interest in "tracer imaging."

Nuclear medicine and breast cancer: a review of current strategies and novel therapies

While breast cancer is still increasing in frequency, new diagnostic procedures are now available to challenge existing procedures and to make diagnosis of breast cancer more accurate and reliable. Mammography remains the standard investigation to reveal disease in an asymptomatic population: it can also be used to diagnose breast cancer in symptomatic patients (e.g. those with palpable breast lumps) and for guiding fine needle aspiration (FNA). Because the majority of breast lumps are benign, the challenge is to distinguish benign from malignant lesions without the use of invasive methods and this has attracted nuclear medicine physicians and medical oncologists to investigate the role of scintigraphic procedures to identify which patients require FNA. This review attempts to shed light on the various scintigraphic methods available which are of potential practical use in the assessment of malignant breast disease as well as looking at the possible role of nuclear medicine in the treatment of advanced disease.

99mTc-MIBI scintimammography as a complement of the mammography in patients with suspected breast cancer. A multicentre experience

The aim of this work has been to evaluate the clinical usefulness of 99mTc-MIBI scintimammography, used as a complement to mammography, in the study of patients with suspected breast cancer. We performed prone breast scintigraphy in 253 patients (268 lesions) with suspected breast cancer. The size and degree of the suspected breast cancer was evaluated by mammography. Diagnosis was established by biopsy. Malignancy was diagnosed in 155 lesions and benign diseases in 113. The results of the scintimammography were a sensitivity of 91%, a specificity of 71%, PPV=81% and NPV=85%. In lesions smaller than 1 cm, sensitivity and specificity were 57% and 100%; in lesions with a diameter of between 1 and 2 cm, these figures were 90% and 72% respectively, and in lesions of more than 2 cm the sensitivity was 99% and the specificity 50%. On mammography, 155 lesions were considered as having a high suspicion of malignancy, whilst 72 were indeterminate and 41 had a low probability. In lesions with a low or indeterminate suspicion of malignancy on mammography, the sensitivity and NPV of the scintimammography were 97% and 98%. Scintimammography is a useful technique in the study of lesions where breast cancer is suspected. Scintimammography results are closely related to tumour size and the degree of mammographic suspicion. Scintimammography can be useful where mammography identifies lesions with a low or indeterminate suspicion of malignancy.

Usefulness of thallium-201 SPECT scintimammography to differentiate benign from malignant breast masses in mammographically dense breasts

The purpose of this study was to assess the usefulness of thallium-201 (Tl-201) single-photon emission-computed tomography (SPECT) scintimammography to differentiate benign from malignant breast masses in 32 female Taiwanese patients with indeterminate mammographic probability of malignancy because of mammographically dense breasts. All breast masses were removed, and final histopathological diagnoses were obtained in all cases. The results showed that thallium-201 SPECT scintimammography findings were true-positive in 22 cases, false-positive in 1 case, true-negative in 7 cases, and false-negative in 2 cases. The diagnostic sensitivity, specificity, and accuracy were 91.7%, 87.5%, and 90.6%, respectively, for detecting breast cancer in mammographically dense breasts. In conclusion, thallium-201 SPECT scintimammography is a useful tool for differentiating benign from malignant breast masses in patients with indeterminate mammograms because of mammographically dense breasts.

Breast imaging in the new era

In the last decade,there have been huge advances in the field of breast imaging.Full field digital mammography systems optimise lesion to background contrast with resultant improvement in the sensitivity of the technique for cancer detection, facilitated by computer-aided detection.Though mammography remains the only established modality for population-based screening, preliminary results from several large studies indicate that magnetic resonance imaging(MRI) has a role in high-risk patients.On the other hand, advances in ultrasound, MRI and nuclear medicine have the potential to greatly improve the specificity of breast imaging with regard to cancer detection and lesion characterisation.A number of new and experimental techniques are being developed which may have great impact in this area and these will be discussed. Though MRI now has an established place in the diagnosis of breast cancer, it is becoming clear that it can directly affect surgical and medical management by enabling assessment of response to chemotherapy and endocrine therapy, and facilitating choice of the most appropriate surgery.Just as the role of MRI has evolved,so too the place of nuclear medicine, particularly positron emission tomography and radio-immunoscintigraphy should become clearer in the next few years.

Noncardiac findings on dual-isotope myocardial perfusion SPECT

BACKGROUND

This study examined the frequency of reporting noncardiac findings (NCFs), such as malignancies from inspection of raw projection images with dual-isotope single photon emission computed tomography (SPECT) perfusion imaging, which could potentially be of greater clinical importance than myocardial perfusion imaging alone. Dual-isotope (ie, rest thallium 201 and stress technetium 99m sestamibi [MIBI] or Tc-99m tetrofosmin [TET]) SPECT myocardial perfusion imaging combines multipotential tracers for noncardiac purposes (Tl-201 for renal or splenic imaging, inflammation, or lymphoma and MIBI or TET for hepatobiliary imaging and detecting increased mitochondrial number or activity in neoplastic processes). These images are optimally interpreted with cinematic inspection of the raw projection data, but this may not be practiced uniformly in every laboratory.

METHODS AND RESULTS

We reviewed 12,526 computer-generated text reports of dual-isotope perfusion SPECT studies from a 6-year period for NCFs. NCFs were categorized by organ and by probability of malignancy: high (eg, focal breast or lung uptake of MIBI or TET), intermediate (eg, lymph node uptake or thyroid abnormalities), or low (eg, filling defects in liver, kidney, spleen, or gall bladder; ascites; or pleural effusions). Confirmatory imaging studies or clinical confirmation for each NCF was sought. There were a total of 207 NCFs identified in 180 reports (1.7% of reports, ranging from 0% to 2.8% of reports of individual interpreters). Of these, 107 NCFs were unsuspected before SPECT; 24% were considered at high probability for malignancy, and 24% were considered intermediate in likelihood of malignancy. Follow-up data were available for 178 NCFs, confirming 88% of these findings, including 82% of breast foci, 62% of lung foci, 86% of hepatobiliary/spleen abnormalities, and 94% of renal abnormalities. The probability of malignancy was highest (82%) in breast or lung foci in which uptake of both Tl-201 and the Tc-99m-labeled agent was present.

CONCLUSIONS

In patients referred for evaluation of myocardial perfusion, NCFs are unusual and require systematic and careful inspection of projection images for their detection. With Tl-201, TET, MIBI, or dual-isotope imaging, detecting and reporting NCFs may occasionally result in life-saving early cancer identification.

Complementary use of scintimammography with 99m-Tc-MIBI to triple diagnostic procedure in palpable and non-palpable breast lesions

PURPOSE

The aim of this study was to determine the clinical value of scintimammography with 99m-Tc-MIBI (Sc) as a complementary method to the triple diagnostic procedure in the diagnosis of breast lesions.

MATERIAL AND METHODS

Ninety-six consecutive patients with 65 palpable and 54 non-palpable breast lesions were included in a prospective study. All lesions were evaluated by clinical examination, mammography and fine-needle-aspiration cytology (FNAC), called triple diagnostic procedure (TD). Prone planar scintimammography with 99m-Tc-MIBI was performed in all patients. Five groups were defined for diagnosis: 1 = normal; 2 = benign; 3 = probably benign; 4 = highly suspect of malignancy; and 5 = malignant. In the calculations, groups 1-3 were considered benign, and 4-5 malignant. All lesions were excised and examined histologically. The additional value of Sc + TD procedure was studied separately for palpable and non-palpable lesions.

RESULTS

Histologically, 83 malignant and 36 benign lesions were found in the 119 breast lesions. Sensitivity for malignancy in palpable lesions of TD alone and of the combination TD + Sc were 95.6% and 100%, respectively. Sensitivity for malignancy in non-palpable lesions of TD and TD + Sc was 89.1% and 97.2%, respectively.

CONCLUSION

Adding scintimammography to the triple diagnostic procedure increased the sensitivity for the detection of both palpable and non-palpable breast cancers, but decreased the specificity.