The application of positron emission tomographic imaging with fluorodeoxyglucose to the evaluation of breast disease

Fructose and prostate cancer: toward an integrated view of cancer cell metabolism

Activation of glucose transporter-1 (Glut-1) gene expression is a molecular feature of cancer cells that increases glucose uptake and metabolism. Increased glucose uptake is the basis for the clinical localization of primary tumors using positron emission tomography (PET) and 2-deoxy-2-[18F]-fluoro-D-glucose (FDG) as a radiotracer. However, previous studies have demonstrated that a considerable number of cancers, which include prostate cancer (CaP), express low to undetectable levels of Glut-1 and that FDG-PET has limited clinical applicability in CaP. This observation could be explained by a low metabolic activity of CaP cells that may be overcome using different hexoses, such as fructose, as the preferred energy source. However, these hypotheses have not been examined critically in CaP. This review article summarizes what is currently known about transport and metabolism of hexoses, and more specifically fructose, in CaP and provides experimental evidences indicating that CaP cells may have increased capacity to transport and metabolize fructose in vitro and in vivo. Moreover, this review highlights recent findings that allow better understanding of how metabolism of fructose may regulate cancer cell proliferation and how fructose uptake and metabolism, through the de novo lipogenesis pathway, may provide new opportunities for CaP early diagnosis, staging, and treatment.

Nuclear Medicine Advances in Breast Cancer Imaging

Primary breast cancer imaging can be done by various means. Mammography is the most widely used technique because of its excellent diagnostic performance, patient compliance, and cost-effectiveness ratio. Other radiological techniques (such as ultrasonography) are indicated in particular circumstances, while some (such as digital mammography and magnetic resonance imaging) seem very promising but are still under evaluation. The recent technological progress in nuclear medicine has resulted in the availability of two diagnostic procedures that have been validated by extensive international clinical experience: scintimammography with Ses-ta-MIBI and positron emission tomography (PET) with fluorodeoxyglucose (FDG). The general advantage of nuclear medicine imaging is that tumor-seeking radiopharmaceuticals accumulate in cancer lesions, which makes scintimammography and PET fundamentally different from the radiological techniques that image the tumor mainly on the basis of morphological alterations. Scintimammography is indicated for the study of breast lesions in patients in whom mammography is non-diagnostic or difficult to interpret; it may be useful also to assess and even predict the response to primary chemotherapy. FDG-PET is increasingly used in oncology and is particularly useful in breast cancer as it gives more accurate information than scintimammography in the evaluation of patients with ambiguous mammographies and in discriminating between viable tumor, fibrotic scar or necrosis following surgery, chemo- or radiotherapy. The FDG uptake in the tumor correlates with the histological grade and potential aggressiveness of breast cancer, which may have prognostic implications. In addition to its usefulness in the study of breast lesions, FDG-PET shows great efficacy in detecting lymph node involvement prior to surgery. Whole-body PET provides information on soft tissue and bone metastases in a single scanning session, and has an important clinical role in detecting recurrent metastatic disease. On the basis of the above-mentioned evidence, nuclear medicine techniques, integrated with radiological techniques, offer an interesting opportunity to improve the diagnostic imaging yield in breast cancer, which will eventually lead to better patient management. This paper reports on the latest developments in this field.

Multimodal breast cancer imaging using coregistered dynamic diffuse optical tomography and digital breast tomosynthesis

Diffuse optical tomography (DOT) is emerging as a noninvasive functional imaging method for breast cancer diagnosis and neoadjuvant chemotherapy monitoring. In particular, the multimodal approach of combining DOT with x-ray digital breast tomosynthesis (DBT) is especially synergistic as DBT prior information can be used to enhance the DOT reconstruction. DOT, in turn, provides a functional information overlay onto the mammographic images, increasing sensitivity and specificity to cancer pathology. We describe a dynamic DOT apparatus designed for tight integration with commercial DBT scanners and providing a fast (up to 1 Hz) image acquisition rate to enable tracking hemodynamic changes induced by the mammographic breast compression. The system integrates 96 continuous-wave and 24 frequency-domain source locations as well as 32 continuous wave and 20 frequency-domain detection locations into low-profile plastic plates that can easily mate to the DBT compression paddle and x-ray detector cover, respectively. We demonstrate system performance using static and dynamic tissue-like phantoms as well as in vivo images acquired from the pool of patients recalled for breast biopsies at the Massachusetts General Hospital Breast Imaging Division.

Role of Optimal Quantification of FDG PET Imaging in the Clinical Practice of Radiology

The combination of fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) and computed tomography (CT) for dual-modality imaging (PET/CT) plays a key role in the diagnosis and staging of FDG-avid malignancies. FDG uptake by the tumor cells offers an opportunity to detect cancer in organs that appear normal at anatomic imaging and to differentiate viable tumor from posttreatment effects. Quantification of FDG uptake has multiple clinical applications, including cancer diagnosis and staging. Dedicated FDG PET/CT-based visual and quantitative criteria have been developed to evaluate treatment response. Furthermore, the level of tumor FDG uptake reflects the biologic aggressiveness of the tumor, predicting the risk of metastasis and recurrence. FDG uptake can be measured with qualitative, semiquantitative, and quantitative methods. Qualitative or visual assessment of PET/CT images is the most common clinical approach for describing the level of FDG uptake. Standardized uptake value (SUV) is the most commonly used semiquantitative tool for measuring FDG uptake. SUV can be measured as maximum, mean, or peak SUV and may be normalized by using whole or lean body weight. SUV measurements provide the basis for quantitative response criteria; however, SUVs have not been widely adopted as diagnostic thresholds for discriminating malignant and benign lesions. Volumetric FDG uptake measurements such as metabolic tumor volume and total lesion glycolysis have shown substantial promise in providing accurate tumor assessment. SUV measurement and other quantification techniques can be affected by many technical, physical, and biologic factors. Familiarity with FDG uptake quantification approaches and their pitfalls is essential for clinical practice and research.

Cellular distribution of Glut-1 and Glut-5 in benign and malignant human prostate tissue

Over-expression of hexose transporters (Gluts), specifically Glut-1, is a common event in human malignancies. In prostate cancer (CaP), however, expression of Gluts has been characterized poorly. In this study, expression and distribution of Glut-1 and Glut-5 proteins were characterized using immunohistochemistry in 76 specimens of benign prostate, 10 specimens of high-grade intraepithelial neoplasia (HGPIN), and 28 specimens of CaP. In addition, mRNA expression of Glut-2, Glut-7, Glut-9, and Glut-11 was analyzed in a set of five specimens of benign prostate and CaP. In benign prostate, Glut-1 localized to the basal cells and to the basolateral membrane of secretory/luminal epithelial cells. Glut-5, however, localized to the apical membrane of secretory/luminal epithelial cells. In HGPIN, Glut-1 was immunohistochemically undetectable. Glut-5, however, localized to the apical membrane of the neoplastic epithelial cells. In CaP, Glut-1 and Glut-5, were immunohistochemically undetectable. However, over-expression of GLUT1 was observed in some specimens of highly proliferative intraductal CaP. Glut-7, Glut-9, and Glut-11 mRNAs were detected in benign prostate and CaP, however, only Glut-11 mRNA was consistently up-regulated in CaP compared to benign prostate. Low levels of expression of Glut-1 protein in the majority of CaP could explain, at least in part, the limited clinical applicability of positron emission tomography using 2-[18F]-fluoro-2-deoxy-D-glucose for imaging CaP. Moreover, expression of Glut-5 in HGPIN suggested that fructose could be utilized as potential metabolic substrate in HGPIN. Understanding the molecular mechanisms involved in regulation/dysregulation of Gluts in CaP could provide insight in the understanding of hexose metabolism in CaP.

Wide-field imaging of fluorescent deoxy-glucose in ex vivo malignant and normal breast tissue

Rapid in situ determination of surgical resection margins during breast cancer surgery would reduce patient time under anesthesia. We present preliminary data supporting the use of a fluorescent glucose analog (2-NBDG) as an optical contrast agent to differentiate freshly excised breast tissue containing cancerous cells from normal breast tissue. Multi-spectral images of 14 breast cancer specimens acquired before and after incubation with 2-NBDG demonstrated increased fluorescent signal in all of the malignant tissue due to increased 2-NBDG consumption. We demonstrate that 2-NBDG has potential as an optical contrast agent to differentiate cancerous from non-cancerous tissue.

Breast cancer

Diagnostic imaging modalities utilized in the care of cancer patients must fulfill several requirements: they must diagnose and characterize tumors with high accuracy, must reliably stage and restage the disease, and should allow for monitoring the effects of therapeutic interventions on the course of the disease. They should impact management by guiding treating physicians to appropriate individualized treatment strategies. There is ample evidence that positron emission tomography (PET) and PET-computed tomography (CT) imaging can meet these requirements. This chapter discusses the role and contributions of PET and PET-CT imaging using (18)F-fluorodeoxyglucose in diagnosing, staging, restaging, and treatment monitoring of breast cancer. Novel molecular imaging probes and devices that have been developed and translated into early clinical research protocols are also introduced.

Incidental breast lesions identified by 18F-fluorodeoxyglucose-positron emission tomography

BACKGROUND

Positron emission tomography (PET) scanning is now part of the standard evaluation for patients with a variety of different malignancies. We describe our experience with breast incidentalomas in a large series of PET scans performed for patients without a known history of breast cancer.

MATERIALS AND METHODS

From March 2000 through June 2007, approximately 45,000 PET scans were performed; 163 had breast findings unrelated to the primary malignancy. In 103 of 163 (63%), findings included physiologic variation, lactation, implants, or benign calcifications. Chart review was conducted in the remaining 60 of 163 patients (37%).

RESULTS

In 20 of 60 patients (33%), no additional evaluation was performed due to advanced stage of the primary malignancy; 40 of 60 (67%) underwent additional imaging and evaluation. In 16 of 40 patients (40%), the lesion resolved on repeat PET; the lesion persisted in 10 of 40 (25%). Additional breast imaging was performed in 14 of 40 (35%). In total, 12 of 40 (30%) underwent biopsy; 7 of 40 (18%) were positive for malignancy.

CONCLUSIONS

In our experience, 29% of breast incidentalomas (7 of 24) with persistent imaging findings were malignant. Further evaluation of these lesions should be based on overall clinical status. In patients where results would not change overall management, biopsy may not be warranted.

PET, PET/CT, and PET/MR Imaging Assessment of Breast Cancer

This review focuses mainly on clinical applications of PET/CT in patients with breast cancer. It discusses the role of 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) PET/CT (and FDG PET) in the diagnosis and initial staging of breast cancer, in monitoring the response of disease to chemotherapy, and in identifying metastatic and recurrent disease. In addition, it discusses the role of MR imaging and potential future hybrid modalities such as PET/MR imaging.

Nutritional channels in breast cancer

Breast cancers increase glucose uptake by increasing expression of the facilitative glucose transporters (GLUTs), mainly GLUT1. However, little is known about the relationship between GLUT1 expression and malignant potential in breast cancer. In this study, expression and subcellular localization of GLUT1 was analysed in vivo in breast cancer tissue specimens with differing malignant potential, based on the Scarff-Bloom-Richardson (SBRI, II, III) histological grading system, and in vitro in the breast cancer cell lines, MDA-MB-468 and MCF-7, and in MDA-MB-468 cells grown as xenografts in nude athymic BALB/c male mice. In situ hybridization analyses demonstrated similar levels of GLUT1 mRNA expression in tissue sections from breast cancers of all histological grades. However, GLUT1 protein was expressed at higher levels in grade SBRII cancer, compared with SBRI and SBRIII, and associated with the expression of the proliferation marker PCNA. Immunolocalization analyses in SBRII cancers demonstrated a preferential localization of GLUT1 to the portions of the cellular membrane that faced neighbouring cells and formed ‘canaliculi-like structures’, that we hypothesize could have a potential role as ‘nutritional channels’. A similar pattern of GLUT1 localization was observed in confluent cultures of MDA-MB-468 and MCF-7, and in MDA-MB-468 cells grown as xenografts, but not in the normal breast epithelial cell line HMEC. However, no relationship between GLUT1 expression and malignant potential of human breast cancer was observed. Preferential subcellular localization of GLUT1 could represent a physiological adaptation of a subset of breast cancer cells that form infiltrative tumours with a nodular growth pattern and that therefore need a major diffusion of glucose from blood vessels.

The relationship between FDG uptake in PET scans and biological behavior in breast cancer

BACKGROUND

Positron emission tomography (PET) is a non-invasive imaging modality used in the diagnosis and staging of breast cancer. However, several factors can affect fluoro-deoxyglucose (FDG) uptake by a tumor. To clarify the parameters that most affect FDG accumulation in tumors, the relationship between standardized uptake values (SUVs) and clinicopathological factors and immunohistopathological analysis was investigated in breast cancer.

MATERIAL AND METHODS

PET studies were performed preoperatively on 37 patients with breast carcinoma. SUVs were counted at one hour (early phase) and at two hours (delayed phase) after FDG injection. The relationships between SUVs and 13 clinical, pathological and immunohistchemical factors were studied.

RESULTS

A significant association was found between FDG accumulation and early and delayed phase mitotic counts (p=0.0018 and 0.0010, respectively), Ki67 positive cell percentage (p=0.0098 and 0.0062, respectively), and nuclear grade (p=0.0232 and 0.0195, respectively). On the other hand, nodal status weakly correlated with the delayed phase (p=0.0907). However, other clinicopathological parameters and immunohistopathological status, which included tumor size, age, histology, estrogen receptor, progesterone receptor and Her2/neu overexpression, did not correlate significantly with FDG uptake.

CONCLUSION

Mitotic count and Ki67 reflect cellular aggressiveness. These parameters were strongly correlated with tracer uptake. Thus our data suggested that the biological behavior of breast cancer is reflected in the variation of FDG uptake by the tumor. However, whether FDG uptake is a true prognostic and predictive factor remains to be confirmed in larger studies over an extended period of time.

F-18 Fluorodeoxyglucose-Positron Emission Tomography Imaging for Primary Breast Cancer and Loco-Regional Staging

Breast cancer is the most common female malignancy in Western countries. The limitations of mammography, ultrasound and MRI do not allow reliable identification of primary breast cancer at early stages. Functional breast imaging with positron emission tomography (PET) and F-18 fluorodeoxyglucose (FDG) enables the visualization of increased glucose metabolism of breast cancer. However, despite the successful identification of primary breast cancer, FDG-PET provides a low sensitivity to detect small tumors. Therefore, FDG-PET does not allow screening of asymptomatic women and cannot be used to exclude breast cancer in patients with suspicious breast masses or abnormal mammography. FDG-PET is a powerful tool for staging of breast cancer patients, but does not detect micrometastases and small tumor infiltrated lymph nodes. Nevertheless, in patients with locally advanced breast cancer, PET accurately determines the extent of disease, particularly the loco-regional lymph node status. Advances in technology, for example the development of dedicated breast imaging devices such as positron emission mammography, hold promise to improve the detection of primary tumors in the future.

Cost-effectiveness of positron emission tomography in breast cancer

PURPOSE

In this study, we used quantitative decision tree modeling to assess the cost-effectiveness of a positron emission tomography (PET)-based management scenario for breast cancer in Canada.

PROCEDURES

Two patient management scenarios were compared (with and without PET). A metaanalysis of studies for the accuracy of PET in staging breast cancer was conducted. Life expectancies were calculated. Management costs were determined from previous cost-effective analyses, management costs from our institutions, and recently published Canadian cost estimates of various procedures.

RESULTS

A cost savings of $695 per person is expected for the PET strategy, with an increase in life expectancy (7.4 days), when compared with the non-PET strategy. This cost savings remained in favor of the PET strategy when subjected to a sensitivity analysis.

CONCLUSIONS

The use of a PET management strategy for the staging of breast cancer is expected to remain economically viable in Canada under various economic conditions.

Positron emission mammography: high-resolution biochemical breast imaging

Positron emission mammography (PEM) provides images of biochemical activity in the breast with spatial resolution matching individual ducts (1.5 mm full-width at half-maximum). This spatial resolution, supported by count efficiency that results in high signal-to-noise ratio, allows confident visualization of intraductal as well as invasive breast cancers. Clinical trials with a full-breast PEM device have shown high clinical accuracy in characterizing lesions identified as suspicious on the basis of conventional imaging or physical examination (sensitivity 93%, specificity 83%, area under the ROC curve of 0.93), with high sensitivity preserved (91%) for intraductal cancers. Increased sensitivity did not come at a cost of reduced specificity. Considering that intraductal cancer represents more than 30% of reported cancers, and is the form of cancer with the highest probability of achieving surgical cure, it is likely that the use of PEM will complement anatomic imaging modalities in the areas of surgical planning, high-risk monitoring, and minimally invasive therapy. The quantitative nature of PET promises to assist researchers interested studying the response of putative cancer precursors (e.g., atypical ductal hyperplasia) to candidate prevention agents.

Imaging in breast cancer: Single-photon computed tomography and positron-emission tomography

Although mammography remains a key imaging method for the early detection and screening of breast cancer, the overall accuracy of this test remains low. Several radiopharmaceuticals have been proposed as adjunct imaging methods to characterize breast masses by single-photon-emission computed tomography (SPECT) and positron-emission tomography (PET). Useful in characterizing indeterminate palpable masses and in the detection of axillary metastases, these techniques are insufficiently sensitive to detect subcentimetric tumor deposits. Their role in staging nodal involvement of the axillary areas therefore currently remains limited. Several enzymes and receptors have been targeted for imaging breast cancers with PET. [¹⁸F]Fluorodeoxyglucose is particularly useful in the detection and staging of recurrent breast cancer and in assessing the response to chemotherapy. Several other ligands targeting proliferative activity, protein synthesis, and hormone and cell-membrane receptors may complement this approach by providing unique information about biological characteristics of breast cancer across primary and metastatic tumor sites.

PET and functional anatomic fusion imaging in lung and breast cancers

Metabolic imaging with PET is an established adjunct to anatomic imaging methods in patients with bronchial and breast cancers. The functional anatomic fusion imaging with PET/CT can further improve staging and restaging of patients. PET/CT can influence the planning of a surgical intervention or radiation treatment at staging and in patients with suspected locoregional recurrence. The use of a PET/CT whole body imaging protocol may identify extended disease earlier than conventional imaging methods and thus influence treatment decisions.

Positron emission tomography in the staging and management of breast cancer

Background

Breast cancer is the commonest cause of cancer death in women in the Western world, and imaging is essential in its diagnosis and staging. Metabolic imaging is a novel approach to improving the detection of cancers, as malignant transformation of cells is often associated with increased metabolic activity. This review assesses the possible role of positron emission tomography (PET) as a single non-invasive imaging modality to replace or complement current imaging and surgical practices in the diagnosis and staging of breast cancer.

Methods and results

A Medline search was performed and articles were cross-referenced with other relevant material. Evaluation of primary breast cancer with PET has shown a sensitivity of between 64 and 100 per cent and a specificity of 33–100 per cent; diagnostic accuracy appears to be related to tumour size. Difficulties arise in altered fluorodeoxyglucose uptake in lobular carcinoma, carcinoma in situ and benign inflammatory breast disease. In axillary staging, sensitivities of between 25 and 100 per cent have been reported, but with a false-negative of up to 20 per cent. In the assessment of distant metastasis and asymptomatic patients with raised levels of tumour markers, PET was superior to conventional imaging modalities.

Conclusion

PET is not a single diagnostic and staging tool that can replace current surgical, histological and radiological staging. Its main role in breast cancer lies in the investigation of metastatic disease and the evaluation of pathological response to various chemotherapeutic regimens.

An introduction to PET-CT imaging

Cancer is one of the leading causes of morbidity and mortality in developed countries such as the United States. Complex clinical decisions about treatment of oncologic patients are largely guided by imaging findings, among other factors. Most radiologic procedures map the anatomy and morphology of tumors with little or no information about their metabolism. Positron emission tomography (PET) performed with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) has proved valuable in providing important tumor-related qualitative and quantitative metabolic information that is critical to diagnosis and follow-up. PET-computed tomography (CT) is a unique combination of the cross-sectional anatomic information provided by CT and the metabolic information provided by PET, which are acquired during a single examination and fused. FDG PET-CT offers several advantages over PET alone; the most important is the ability to accurately localize increased FDG activity to specific normal or abnormal anatomic locations, which may be difficult or even impossible with PET alone. Understanding the principles of FDG PET-CT and the optimal scanning techniques and recognizing the potential pitfalls and limitations are important for advantageous use of this imaging modality.

Current and future uses of positron emission tomography in breast cancer imaging

Positron emission tomography using (18)F-fluorodeoxyglucose (FDG-PET) has been used for the detection, staging, and response monitoring in breast cancer patients. Although studies have proven its accuracy in detection of the primary tumor and axillary staging, its most important current clinical application is in detection and defining the extent of recurrent or metastatic breast cancer and for monitoring response to therapy. PET is complementary to conventional methods of staging in that it provides better sensitivity in detecting nodal and lytic bone metastases; however, it should not be considered a substitute for conventional staging studies, including computed tomography and bone scintigraphy. FDG uptake in the primary tumor carries prognostic information, but the underlying biochemical mechanisms that are responsible for enhanced glucose metabolism have not been completely elucidated. Future work using other PET tracers besides FDG will undoubtedly help our understanding of tumor biology, improve our ability to measure and predict response and help tailor therapy to individual patients.

18F-2-Fluoro-2-Deoxy-d-Glucose Positron Emission Tomography in Staging of Locally Advanced Breast Cancer

Purpose

To prospectively evaluate the effect of adding whole-body 18F-2-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) to conventional screening for distant metastases in patients with locally advanced breast cancer (LABC).

Patients and Methods

All women with LABC referred for participation in the LABC Spinoza trial were considered eligible for this study. Patients were included if chest x-ray, bone scan, liver ultrasound, or computed tomography scan performed by the referring physician failed to reveal distant metastases. They underwent whole-body FDG PET scanning before therapy. Patients with subsequently proven distant metastases were switched to alternative forms of chemotherapy, hormonal therapy, or both.

Results

Among the 48 patients evaluated with PET, 14 had abnormal FDG uptake, and metastases were suspected in 12. After simple clinical evaluation (plain x-ray, history), 10 sites that were suggestive of abnormality remained. Further work-up revealed that four sites were metastases. Proven false positivity occurred in one patient with sarcoidosis. In the other five patients, the reason for abnormal FDG uptake (liver, lung, bone) remained unclear, and patients were treated as planned. Eleven months later, distant metastases were found in one patient at sites unrelated to the previous FDG uptake.

Conclusion

The addition of FDG PET to the standard work-up of patients with LABC may lead to the detection of unexpected distant metastases. This may contribute to a more realistic stratification between patients with true stage III breast cancer and those who are in fact suffering from stage IV disease. Abnormal PET findings should be confirmed to prevent patients from being denied appropriate treatment.

Prospective multicenter study of axillary nodal staging by positron emission tomography in breast cancer: a report of the staging breast cancer with PET Study Group

PURPOSE

To determine the accuracy of positron emission tomography with fluorine-18-labeled 2-fluoro-2-deoxy-d-glucose (FDG-PET) in detecting axillary nodal metastases in women with primary breast cancer.

PATIENTS AND METHODS

In this prospective multicenter study, 360 women with newly diagnosed invasive breast cancer underwent FDG-PET. Images were blindly interpreted by three experienced readers for abnormally increased axillary FDG uptake. Imaging results from 308 assessable axillae were compared with axillary node pathology.

RESULTS

For detecting axillary nodal metastasis, the mean estimated area under the receiver operator curve for the three readers was 0.74 (range, 0.70 to 0.76). If at least one probably or definitely abnormal axillary focus was considered positive, the mean (and range) sensitivity, specificity, and positive and negative predictive values for PET were 61% (54% to 67%), 80% (79% to 81%), 62% (60% to 64%), and 79% (76% to 81%), respectively. False-negative axillae on PET had significantly smaller and fewer tumor-positive lymph nodes (2.7) than true-positive axillae (5.1; P <.005). Semiquantitative analysis of axillary FDG uptake showed that a nodal standardized uptake value (lean body mass) more than 1.8 had a positive predictive value of 90%, but a sensitivity of only 32%. Finding two or more intense foci of tracer uptake in the axilla was highly predictive of axillary metastasis (78% to 83% positive predictive value), albeit insensitive (27%).

CONCLUSION

FDG-PET has moderate accuracy for detecting axillary metastasis but often fails to detect axillae with small and few nodal metastases. Although highly predictive for nodal tumor involvement when multiple intense foci of tracer uptake are identified, FDG-PET is not routinely recommended for axillary staging of patients with newly diagnosed breast cancer.

Role of positron emission tomography in the management of breast cancer

Positron emission tomography (PET) is an imaging modality that utilises tracers based on biologically important compounds and can be used to study in vivo tissue function. This article reviews the current status of PET imaging in breast disease. The positron emitting glucose analogue 18F-FDG is used to image tissue glycolysis and has been extensively evaluated. Studies have shown that 18F-FDG PET has a high sensitivity and specificity for the detection of primary breast cancers, however its use is not superior that of conventional imaging modalities. Considerable interest is now focussing on the application of PET to non-invasively determine the lymph node status of patients with breast cancer and to predict and evaluate tumour response to chemotherapy. Relatively low cost gamma camera systems are now available that are capable of PET imaging, and thus it may therefore be possible to perform PET imaging in the majority of hospitals.

Measuring [(18)F]FDG uptake in breast cancer during chemotherapy: comparison of analytical methods

Over the years several analytical methods have been proposed for the measurement of glucose metabolism using fluorine-18 fluorodeoxyglucose ([(18)F]FDG) and positron emission tomography (PET). The purpose of this study was to evaluate which of these (often simplified) methods could potentially be used for clinical response monitoring studies in breast cancer. Prior to chemotherapy, dynamic [(18)F]FDG scans were performed in 20 women with locally advanced ( n=10) or metastasised ( n=10) breast cancer. Additional PET scans were acquired after 8 days ( n=8), and after one, three and six courses of chemotherapy ( n=18, 10 and 6, respectively). Non-linear regression (NLR) with the standard two tissue compartment model was used as the gold standard for measurement of [(18)F]FDG uptake and was compared with the following methods: Patlak graphical analysis, simplified kinetic method (SKM), SUV-based net influx constant ("Sadato" method), standard uptake value [normalised for weight, lean body mass (LBM) and body surface area (BSA), with and without corrections for glucose (g)], tumour to non-tumour ratio (TNT), 6P model and total lesion evaluation (TLE). Correlation coefficients between each analytical method and NLR were calculated using multilevel analysis. In addition, for the most promising methods (Patlak, SKM, SUV(LBMg) and SUV(BSAg)) it was explored whether correlation with NLR changed with different time points after the start of therapy. Three methods showed excellent correlation ( r>0.95) with NLR for the baseline scan: Patlak10-60 and Patlak10-45 ( r=0.98 and 0.97, respectively), SKM40-60 ( r=0.96) and SUV(LBMg) ( r=0.96). Good correlation was found between NLR and SUV-based net influx constant, TLE and SUV(BSAg) (0.90< r<0.95). The 6P model and TNT had the lowest correlation ( r<or=0.84). SUV was least accurate in predicting changes in [(18)F]FDG uptake over time during therapy. For all methods, correlation with NLR was significantly lower for bone metastases than for other (primary or metastatic) tumour lesions ( P<0.05). In conclusion, three methods with different degrees of complexity appear to be promising alternatives to NLR for measuring glucose metabolism in breast cancer: Patlak, SKM and SUV (normalised for LBM and with a correction for plasma glucose).

Positron emission tomography in diagnosis and management of invasive breast cancer: current status and future perspectives

[18F]fluorodeoxyglucose positron emission tomography (FDG-PET) is a metabolic imaging modality that has increasing applications in oncology, neurology, and cardiology. Among the oncology applications, breast cancer is one of the most extensively studied diseases. FDG-PET has been performed for diagnosis, staging, and restaging of invasive breast cancer and for monitoring responsiveness to therapies. At the present time, the results of FDG-PET in detection of primary breast cancer and axillary staging are mixed and inconclusive. However, results demonstrating the superiority of FDG-PET over anatomic imaging modalities in detection of distant metastasis, recurrence, and monitoring therapies are relatively well documented. These applications have been accepted by medical professionals and the public, as evidenced by a recent decision by the Centers for Medicare and Medicaid Services (formerly Health Care Financing Agency) to provide coverage for the procedure. Future trends in this exciting area include development of novel breast cancer-specific PET radiopharmaceuticals and use of dedicated breast PET technologies for scans of breast/axillary lesions. PET/computed tomography technology, which combines anatomic and molecular/biochemical information, is also rapidly proliferating and should help to further improve the management of patients with breast cancer. The role of FDG-PET in breast cancer is increasing and evolving, and this metabolic imaging modality, in conjunction with newer tracers and other anatomic imaging methods, should improve diagnosis and management of patients with breast cancer

Breast cancer imaging with PET and SPECT agents: an in vivo comparison

Several radiopharmaceuticals and imaging techniques are proposed for breast cancer imaging. Since limited data are available of the uptake of SPECT and PET radiopharmaceuticals in malignant breast tumors and their metastases the aim of this study was to compare the uptake values and to correlate these data with imaging findings.

METHODS

We have studied the uptake of F-18 FDG, Tc-99m MIBI and Tc-99m (V)DMSA in 31 tumors using immunosuppressed rats implanted with HH-16 clone 4 mammary tumor cells. Tumor gamma camera and PET imaging was performed to gain biokinetic data and uptake values by ROI-analysis.

RESULTS

Tumor uptake was highest for F-18 FDG > Tc-99m (V)DMSA > Tc-99m MIBI. The uptake ratios (tumor to muscle) correlated well with the ratios calculated by ROI-analysis determined by imaging.

CONCLUSIONS

In this in-vivo model, F-18 FDG revealed the best uptake and imaging properties and may be the radiopharmaceutical of choice for routine breast cancer imaging.

Fluorine-18 FDG-PET in detecting local recurrence and distant metastases in breast cancer--Taiwanese experiences

Fluorine-18 fluorodeonyglucose positron emission tomography (FDG-PET) was used to detect local recurrence, axillary lymph node (LN) involvement and distant metastases in patients with breast cancer. Thirty-six female patients with breast cancer s/p operation underwent FDG-PET studies. Findings were confirmed by histology following surgery and/or biopsy or negative follow-up results over a period of at least one year. In the evaluation of local recurrence, the diagnostic sensitivity, specificity, and accuracy of FDG-PET was 100, 96.8, and 97.2%, respectively. In the evaluation of axillary LN involvement, sensitivity, specificity, and accuracy was 80, 100, and 97.2%, respectively. In the evaluation of distant metastases, the diagnostic sensitivity, specificity, and accuracy was 83.3, 85.2, and 84.4%, respectively. The FDG-PET is a useful diagnostic tool in detecting local recurrence, axillary LN involvement, and distant metastasis.

Comparison of fluorodeoxyglucose positron emission tomography and "conventional diagnostic procedures" for the detection of distant metastases in breast cancer patients

The presence of distant metastases is the main prognostic factor in patients with breast cancer and has a significant influence in the choice of therapy. Therefore, chest X-ray, bone scintigraphy and ultrasound of the abdomen are performed to detect distant metastases at diagnosis and follow-up. Fluorodeoxyglucose positron emission tomography (FDG PET) has been shown to provide sensitive detection of primary tumour and metastases for many tumour entities, but little information is available about the diagnostic value for breast cancer patients. This study retrospectively compared FDG PET for detection of metastatic disease with chest X-ray, bone scintigraphy and ultrasound of the abdomen, referred to as "conventional diagnostic procedures" (CDPs), in 50 breast cancer patients. Imaging procedures were analysed in a blinded fashion with the results classified as "no evidence of metastases", "equivocal" and "evidence of metastases". Clinical follow-up and the results of other imaging modalities including computed tomography and magnetic resonance imaging were used to determine if metastases were present. FDG PET identified metastatic disease with a sensitivity and specificity of 86% and 90% as compared to 36% and 95% for CDPs, respectively. Regarding "equivocal" and "evidence of metastases" as positive, the sensitivity of CDPs increased to 57% with a corresponding specificity of 81%, whereas sensitivity and specificity of FDG PET remained unchanged. Regarding different localities of metastases the sensitivity of FDG PET was superior in the detection of pulmonary metastases and especially of lymph node metastases of the mediastinum in comparison to chest X-ray, whereas the sensitivity of FDG PET in the detection of bone and liver metastases was of the same magnitude as compared with bone scintigraphy and ultrasound of the abdomen.

The Role of 18F-FDG-PET in the Local/Regional Evaluation of Women with Breast Cancer

PURPOSE

In women with breast cancer, knowledge of the local/regional extent of the tumor is essential for staging, treatment planning, monitoring response to therapy, and follow-up. Positron emission tomography (PET) is an important imaging test which can detect tumor at multiple sites in women with breast cancer. We compared the ability of PET to provide a comprehensive view of the local/regional extent of tumor in women with stage I, II and stage III, IV breast cancer.

MATERIALS AND METHODS

Forty-six women with breast cancer underwent PET using 18F-FDG. 18FDG uptake in the breast primary tumor, associated skin, axillary and internal mammary lymph nodes, and the contralateral breast was determined qualitatively, and correlated with histologic, clinical and radiographic findings.

RESULTS

Twenty-four patients were premenopausal and 22 were postmenopausal, with the following distribution according to clinical stage: stage I--2 patients, stage II--16, stage III--16, stage IV--12 patients. Among stage I, II patients, the sensitivity for detection of the primary tumor was 83.3%, and for detection of axillary lymph node metastases was 42.9%. 18FDG-PET was negative for the breast skin, contralateral breast, and internal mammary lymph nodes in all stage I, II patients, in agreement with clinical and radiographic findings. Among 28 stage III, IV patients, the sensitivity of 18FDG-PET for detection of the primary tumor was 90.5%, and for detection of axillary lymph node metastases 83.3%. Fourteen patients had clinically advanced changes in the skin, and the sensitivity of PET for detection of skin changes was 76.9%. 18FDG-PET was positive in the internal mammary lymph nodes in 25.0%, and negative in the contralateral breast in all patients with stage III, IV breast cancer. 18FDG-PET was studied in 10 patients following neoadjuvant chemotherapy, and showed a strong correlation with clinical response, and with clinical and pathological findings post-treatment at multiple local/regional sites.

CONCLUSION

18FDG-PET can provide a comprehensive image of local/regional tumor in women with breast cancer. 18FDG-PET may play a greater role in women with stage III, IV breast cancer because of increased sensitivity and the increased involvement of multiple local/regional sites with tumor.

Use of serial FDG PET to measure the response of bone-dominant breast cancer to therapy

RATIONALE AND OBJECTIVES

The authors performed this study to determine the feasibility of using quantitative 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) to monitor the response of breast cancer bone metastases to therapy.

MATERIALS AND METHODS

Twenty-four women with stage IV bone-dominant breast carcinoma were included in this study. Whole-body FDG PET imaging was performed at serial time points during the course of therapy. FDG PET scans were interpreted quantitatively by using the maximum standard uptake value (SUV) of the most conspicuous bone lesion at baseline FDG PET. PET results were compared to the overall assessment of response (response, stable disease, progressive disease) with a combination of conventional imaging, change in tumor marker values, and subjective symptom changes by experienced medical oncologists blinded to the findings at FDG PET. Changes in FDG SUV were also correlated quantitatively to the changes in a particular tumor marker (CA 27.29).

RESULTS

The changes in FDG SUV with therapy showed correlation with the overall clinical assessment of response (P < .01). The percentage change in FDG uptake with therapy showed strong correlation with the percentage change in tumor marker value (P < .01).

CONCLUSION

Preliminary results indicate that serial whole-body FDG PET can help quantitatively assess the response of breast cancer bone metastases to therapy. Prospective trials are needed to further investigate its accuracy.

Should FDG PET be used to decide whether a patient with an abnormal mammogram or breast finding at physical examination should undergo biopsy?

RATIONALE AND OBJECTIVES

The purpose of this systematic review was to assess the performance of fluorodeoxyglucose positron emission tomography (PET) in the differential diagnosis of benign from malignant lesions among patients with abnormal mammograms or a palpable breast mass and to examine the effects of PET findings on patient care and health outcomes.

MATERIALS AND METHODS

A search of the MEDLINE and CancerLit databases covered articles entered between January 1966 and March 2001. Thirteen articles met the selection criteria. Each article was assessed for study quality characteristics. Meta-analysis was performed with a random effects model and a summary receiver operating characteristic curve.

RESULTS

A point on the summary receiver operating characteristic curve was selected that reflected average performance, with an estimated sensitivity of 89% and a specificity of 80%. When the prevalence of malignancy is 50%, 40% of all patients would benefit by avoiding the harm of a biopsy with negative biopsy results. The risk of a false-negative result, leading to delayed diagnosis and treatment, is 5.5%. The negative predictive value is 87.9%; thus, the false-negative risk is 12.1%. For a patient with a negative PET scan, a 12% chance of missed or delayed diagnosis of breast cancer is probably too high to make it worth the 88% chance of avoiding biopsy of a benign lesion.

CONCLUSION

The evidence does not favor the use of fluorodeoxyglucose PET to help decide whether to perform biopsy. Available studies omit a critical segment of the biopsy population with indeterminate mammograms or nonpalpable masses, for which no conclusions can be reached.

Nuclear medicine in primary breast cancer imaging

The application of nuclear medicine techniques to study patients with breast cancer has recently raised its profile, particularly in the investigation 'indeterminate mammographic lesions'. This review briefly points out some of the difficulties encountered with other more conventional imaging modalities and describes the radionuclide techniques most frequently employed in the investigation of those patients with breast cancer. Both planar and single photon emission tomography methods are discussed including the use of monoclonal antibodies, perfusion ligands, receptor binding hormones and other specific radiotracers, non-specific tumour markers, as well as deoxyglucose and other amino acids labelled with positron emitting radionuclides.

Positron emission tomography for the diagnosis of breast cancer

This article reviews the literature on breast imaging with [18F]fluorodeoxyglucose positron emission tomography (FDG PET). In clinical applications, there is currently no defined role for detecting primary breast cancer. The limited sensitivity of FDG PET does not allow the exclusion of malignancy, in particular small breast carcinomas, micrometastases and small, tumour infiltrated lymph nodes. However, in advanced stages, PET accurately determines the extent of disease, including the loco-regional lymph node status. Furthermore, whole-body PET imaging promises a high diagnostic accuracy for detecting recurrent or metastatic breast carcinoma. Future clinical applications may include monitoring therapeutic effects.

New modalities in breast imaging: digital mammography, positron emission tomography, and sestamibi scintimammography

Digital mammography, PET, and sestamibi scintimammography are three new modalities in breast imaging. DM has advantages over film-screen mammography in image storage, retrieval, and processing and may lower the recall rate. Computer-aided detection may increase the sensitivity of mammographic screening without a substantial reduction in specificity. Whereas PET and sestambi scintimammography are not useful in breast cancer screening, PET may play a role in detecting nodal metastases and monitoring treatment response, and sestamibi scintimammography in selected cases may serve as an adjunct to conventional imaging. The cost-effectiveness of these new modalities remains to be evaluated, but all have the potential to significantly advance the diagnosis and management of women with breast cancer.

Positron emission tomography scanning: current and future applications

Whole-body positron emission tomography (PET) imaging with (18)F deoxyglucose (FDG) is a molecular imaging modality that detects metabolic alterations in tumor cells that are common to neoplastic cells. FDG-PET has recently been approved by the Health Care Finance Administration for Medicare reimbursement for diagnosing, staging, and restaging lung cancer, colorectal cancer, lymphoma, melanoma, head and neck cancer, and esophageal cancer. This review discusses the scientific evidence that led to the emergence of PET imaging as an accepted clinical tool in patients with solitary pulmonary nodules, lung cancer, colorectal cancer, melanoma, lymphoma, breast cancer, and other cancers. When possible, we compare the performance of PET to that of anatomical imaging. We discuss future clinical applications of this imaging modality.

Positron emission tomography and sentinel lymph node dissection in breast cancer

Sentinel lymph node dissection (SLND) is emerging as the preferred method of axillary staging for breast cancer patients. To further the use of noninvasive techniques in breast cancer, positron emission tomography (PET) scans have been considered as an alternative axillary staging modality. In order to compare the 2 modalities, we studied 15 invasive breast cancer patients who had undergone a preoperative PET scan before sentinel lymphadenectomy. PET scans were compared to axillary pathology results, which were defined as the greatest diameter of nodal metastases. Primary tumor sizes ranged from 0.5 cm to 5.0 cm (median,1.5 cm) and all were ductal in origin except for 1 invasive lobular and 1 mucinous carcinoma. Ten women had completion axillary dissections. Sentinel lymph node dissection was successful in all patients with completion dissections and no false-negative results. Five patients had sentinel node metastases, but PET scans identified only 1 of these patients, resulting in 4 false-negative PET scans. Missed metastases ranged in size from a micrometastatic focus identified only by immunohistochemistry to a nodal tumor measuring 11 mm in diameter. In addition, 1 woman with a PET-positive axilla was tumor free by SLND and remains free of axillary recurrence 29 months postoperatively. Two women had mediastinal uptake by PET scanning and were found to be tumor free after computerized tomography. The results of this preliminary study suggest that PET scanning using current techniques can be used as an adjunct to SLND rather than as an alternative staging technique.

[(18F)-fluoro-2-deoxyglucose PET in imaging of gynecologic cancers]

Although gynaecological cancers are not currently part of the clinical indications in the French registration for [18F]-fluoro-2-deoxyglucose (FDG), various studies indicate in this context a potential clinical benefit of imaging with this radiopharmaceutical and PET, a new imaging modality that can be performed either with a dedicated machine or with a "hybrid" gamma-camera (CDET). The potential indications of FDG-PET in mammary, ovarian or cervical cancers are reviewed according to the diagnostic phase: screening, tumour characterisation, staging, therapeutic follow-up and search for recurrence. By pooling the published results, the accuracy of FDG-PET could be estimated with a reasonable precision in various clinical settings: characterisation of a breast tumour (598/696 = 86%), lymph node invasion in breast cancer (525/602 = 87%), recurrence of breast cancer (114/127 = 90%), characterisation of adnexal masses (130/176 = 78%), recurrence of ovarian cancer (152/172 = 88%), lymph node invasion in cervical cancer (98/103 = 95%). Authors also present original data concerning their experience of recurrence detection with CDET in breast or ovarian cancers. In 44 patients suspicious of recurrence of breast cancer, FDG-CDET sensitivity was 94%, specificity 82% and accuracy 91%; in 18 patients suspicious of recurrence of ovarian cancer, specificity, sensitivity and accuracy were 100%. The impact of dedicated PET and CDET examinations performed by our team during year 2000, led, according to 63 forms returned to us, to a modification of stage in 48% of breast cancers, 36% of ovarian cancers, 43% of cervical cancers and above all induced a modification in patients' management in respectively 69%, 64% and 60% of cases, more than the average rate in cancer patients which was 50%. No significant difference was observed between clinical impact of dedicated PET and CDET examinations.

Positron emission tomography imaging in oncology

The applications for FDG-PET imaging are rapidly growing and accepted in the field of oncology. FDG-PET imaging does not replace other imaging modalities, such as CT, but seems to be very helpful in specific situations where CT has known limitations, such as differentiation of benign from malignant indeterminate lesions on CT, differentiation of post-treatment changes versus recurrent tumor, differentiation of benign from malignant lymph nodes, and monitoring therapy. The biggest use of FDG-PET presently is in N and M staging of various body tumors. The addition of FDG-PET in the evaluation of oncologic patients in well-defined algorithms including a combination of imaging studies seems to be cost effective by accurately identifying patients who benefit from invasive procedures and saving unnecessary costly invasive procedures on patients who do not benefit from them. Although PET imaging may decrease the cost of health care by reducing the number of invasive procedures, implementation of clinical PET has been hindered by the high cost of the purchase, operation expenses, and maintenance of PET systems; the need for immediate access to a source of 18F (owing to the 110-minute half-life); and the limited reimbursement for clinical procedures by third-party payers. These combined factors have resulted in the development by manufacturers of hybrid gamma camera systems capable of performing positron imaging. These systems can be used to image conventional radiopharmaceuticals used in general nuclear medicine and positron-emitting radiopharmaceuticals. The performance of these camera-based PET systems has improved markedly over the past few years with the introduction of thicker NaI (T1) crystals, iterative reconstruction algorithms, and attenuation correction. These new developments in medical imaging instrumentation have contributed to the expansion of the number of cyclotrons, and have driven the concept of commercial FDG distribution centers.