Comparison of FDG-PET with MIBI-SPECT in the detection of breast cancer and axillary lymph node metastasis

Diagnostic Values of 8 Different Imaging Modalities for Preoperative Detection of Axillary Lymph Node Metastasis of Breast Cancer: A Bayesian Network Meta-analysis

OBJECTIVE

This study aimed to compare diagnostic performances of 8 different imaging modalities for preoperative detection of axillary lymph node (LN) metastasis in patients with breast cancer by performing a network meta-analysis (NMA) using direct comparison studies with 2 or more imaging techniques.

MATERIALS AND METHODS

PubMed, Cochrane, and Embase were searched for the studies evaluating the performances of 8 different imaging modalities for preoperative axillary LN staging in patients with breast cancer. The NMA was performed in patient-based analyses. The consistency was evaluated by examining the agreement between direct and indirect treatment effects, and publication bias was assessed by funnel plot asymmetry tests. The surface under the cumulative ranking curve (SUCRA) values were obtained to calculate the probability of each imaging modality being the most effective diagnostic method.

RESULTS

A total of 2197 patients from 22 direct comparison studies using 8 different imaging modalities for preoperative detection of axillary LN metastasis in patients with breast cancer were included. For preoperative detection of axillary LN metastasis of breast cancer, elastography showed the highest SUCRA values of sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and diagnostic odds ratio. In addition, fluorine-18 fluorodeoxyglucose positron emission tomography (PET) or PET/computed tomography, fluorine-18 fluorodeoxyglucose PET/magnetic resonance, and contrast-enhanced computed tomography showed high SUCRA values.

CONCLUSION

Elastography showed the highest SUCRA values. Seven imaging modalities showed the complementary diagnostic roles for preoperative detection of axillary LN metastasis in patients with breast cancer, except mammography.

ACR Appropriateness Criteria® Evaluation of Nipple Discharge

Appropriate imaging evaluation of nipple discharge depends the nature of the discharge. Imaging is not indicated for women with physiologic nipple discharge. For evaluation of pathologic nipple discharge, multiple breast imaging modalities are rated for evidence-based appropriateness under various scenarios. For women age 40 or older, mammography or digital breast tomosynthesis (DBT) should be the initial examination. Ultrasound is usually added as a complementary examination, with some exceptions. For women age 30 to 39, either mammogram or ultrasound may be used as the initial examination on the basis of institutional preference. For women age 30 or younger, ultrasound should be the initial examination, with mammography/DBT added when ultrasound shows suspicious findings or if the patient is predisposed to developing breast cancer. For men age 25 or older, mammography/DBT should be performed initially, with ultrasound added as indicated, given the high incidence of breast cancer in men with pathologic nipple discharge. Although MRI and ductography are not usually appropriate as initial examinations, each may be useful when the initial standard imaging evaluation is negative. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Technetium glucose complexes as potential cancer imaging agents

GLUT's (facilitative glucose transporters) over-expression in tumor cells has allowed the detection of several cancer types, using a glucose analogue ((18)F-FDG) with PET images, worldwide. New glucose analogs radiolabeled with (99m)Tc could be a less-expensive and more accessible alternative for diagnosis using SPECT imaging. d-Glucose ((99m)Tc-IDAG) and 2-d-deoxyglucose ((99m)Tc-AADG) organometallic complexes were proposed and studied as potential (18)F-FDG surrogates. The glucose complexes were prepared and evaluated as potential cancer imaging agents, in a melanoma tumor model. Iminodiacetic acid (IDA) and aminoacetate (AA) moieties were chosen as chelating system for radiolabeling with (99m)Tc. Tumor uptake of the formed complexes was evaluated in B16 murine cell line in vitro and in vivo in melanoma bearing C57BL/6 mice. In vitro and in vivo studies were conducted with (18)F-FDG in order to compare the uptake of (99m)Tc-glucose complexes in the tumor model. IDAG and AADG compounds were synthesized and radiolabeled with (99m)TcO4(-) to obtain the (99m)Tc-IDAG and (99m)Tc-AADG complexes in high yield and stability. In vitro cell studies showed maximum uptake at 60 min for complexes, (99m)Tc-IDAG and (99m)Tc-AADG, with 6% and 2%, respectively. Biodistribution studies showed high tumor uptake one hour post-injection, reaching tumor-to-muscle ratios of 12.1 ± 3.73 and 2.88 ± 1.40 for (99m)Tc-IDAG and (99m)Tc-AADG, respectively. SPECT and micro-SPECT-CT images acquired after the injection of (99m)Tc-IDAG showed accumulation in tumor sites, suggesting that this glucose complex would be a promising candidate for cancer imaging.

High-resolution 3D micro-CT imaging of breast microcalcifications: a preliminary analysis

BACKGROUND

Detection of microcalcifications on mammograms indicates the presence of breast lesion, and the shapes of the microcalcifications as seen by conventional mammography correlates with the probability of malignancy. This preliminary study evaluated the 3D shape of breast microcalcifications using micro-computed tomography (micro-CT) and compared the findings with those obtained using anatomopathological analysis.

METHODS

The study analyzed breast biopsy samples from 11 women with findings of suspicious microcalcifications on routine mammograms. The samples were imaged using a micro-CT (SkyScan 1076) at a resolution of 35 μm. Images were reconstructed using filtered back-projection and analyzed in 3D using surface rendering. The samples were subsequently analyzed by the pathology service. Reconstructed 3D images were compared with the corresponding histological slices.

RESULTS

Anatomopathological analysis showed that 5 of 11 patients had ductal breast carcinoma in situ. One patient was diagnosed with invasive ductal carcinoma.Individual object analysis was performed on 597 microcalcifications. Malignant microcalcifications tended to be thinner and to have a smaller volume and surface area, while their surface area-to-volume ratio was greater than that of benign microcalcifications. The structure model index values were the same for malignant and benign microcalcifications.

CONCLUSIONS

This is the first study to use micro-CT for quantitative 3D analysis of microcalcifications. This high-resolution imaging technique will be valuable for gaining a greater understanding of the morphologic characteristics of malignant and benign microcalcifications. The presence of many small microcalcifications can be an indication of malignancy. For the larger microcalcifications, 3D parameters confirmed the more irregular shape of malignant microcalcifications.

Optical imaging in breast cancer diagnosis: the next evolution

Breast cancer is one of the most common cancers among the population of the Western world. Diagnostic methods include mammography, ultrasound, and magnetic resonance; meanwhile, nuclear medicine techniques have a secondary role, being useful in regional assessment and therapy followup. Optical imaging is a very promising imaging technique that uses near-infrared light to assess optical properties of tissues and is expected to play an important role in breast cancer detection. Optical breast imaging can be performed by intrinsic breast tissue contrast alone (hemoglobin, water, and lipid content) or with the use of exogenous fluorescent probes that target specific molecules for breast cancer. Major advantages of optical imaging are that it does not use any radioactive components, very high sensitivity, relatively inexpensive, easily accessible, and the potential to be combined in a multimodal approach with other technologies such as mammography, ultrasound, MRI, and positron emission tomography. Moreover, optical imaging agents could, potentially, be used as “theranostics,” combining the process of diagnosis and therapy.

Comparative study of the value of dual tracer PET/CT in evaluating breast cancer

The present study was conducted to assess the relationship between tumor uptake and pathologic findings using dual-tracer PET/computed tomography (CT) in patients with breast cancer. Seventy-four patients with breast cancer (mean age 54 years) who underwent (11)C-choline and 2-[(18)F]fluoro-2-deoxy-d-glucose ((18)F-FDG) PET/CT prior to surgery on the same day were enrolled in the present study. Images were reviewed by a board-certified radiologist and two nuclear medicine specialists who were unaware of any clinical information and a consensus was reached. Uptake patterns and measurements of dual tracers were compared with the pathologic findings of resected specimens as the reference standard. Mean (±SD) tumor size was 5.9 ± 3.2 cm. All primary tumors were identified on (18)F-FDG PET/CT and (11)C-choline PET/CT. However, (18)F-FDG PET/CT demonstrated focal uptake of the primary tumor with (n = 38; 51%) or without (n = 36; 49%) diffuse background breast uptake. Of the pathologic findings, multiple logistic regression analysis revealed an independent association between fibrocystic change and diffuse background breast uptake (odds ratio [OR] 8.57; 95% confidence interval [CI] 2.86-25.66; P < 0.0001). Tumors with higher histologic grade, nuclear grade, structural grade, nuclear atypia, and mitosis had significantly higher maximum standardized uptake values (SUV(max)) and tumor-to-background ratios (TBR) for both tracers. Multiple logistic regression analysis revealed that only the degree of mitosis was independently associated with a high SUV(max) (OR 7.45; 95%CI 2.21-25.11; P = 0.001) and a high TBR (OR 5.41; 95%CI 1.13-25.96; P = 0.035) of (11)C-choline PET/CT. In conclusion, (11)C-choline may improve tumor delineation and reflect tumor aggressiveness on PET/CT in patients with breast cancer.

Semiquantitative analysis of maximum standardized uptake values of regional lymph nodes in inflammatory breast cancer: is there a reliable threshold for differentiating benign from malignant?

RATIONALE AND OBJECTIVES

The aim of this study was to determine an optimum standardized uptake value (SUV) threshold for identifying regional nodal metastasis on 18F-fluorodeoxyglucose (FDG) positron emission tomographic (PET)/computed tomographic (CT) studies of patients with inflammatory breast cancer.

MATERIALS AND METHODS

A database search was performed of patients newly diagnosed with inflammatory breast cancer who underwent 18F-FDG PET/CT imaging at the time of diagnosis at a single institution between January 1, 2001, and September 30, 2009. Three radiologists blinded to the histopathology of the regional lymph nodes retrospectively analyzed all 18F-FDG PET/CT images by measuring the maximum SUV (SUVmax) in visually abnormal nodes. The accuracy of 18F-FDG PET/CT image interpretation was correlated with histopathology when available. Receiver-operating characteristic curve analysis was performed to assess the diagnostic performance of PET/CT imaging. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated using three different SUV cutoff values (2.0, 2.5, and 3.0).

RESULTS

A total of 888 regional nodal basins, including bilateral axillary, infraclavicular, internal mammary, and supraclavicular lymph nodes, were evaluated in 111 patients (mean age, 56 years). Of the 888 nodal basins, 625 (70%) were negative and 263 (30%) were positive for metastasis. Malignant lymph nodes had significantly higher SUVmax than benign lymph nodes (P < .0001). An SUVmax of 2.0 showed the highest overall sensitivity (89%) and specificity (99%) for the diagnosis of malignant disease.

CONCLUSIONS

SUVmax of regional lymph nodes on 18F-FDG PET/CT imaging may help differentiate benign and malignant lymph nodes in patients with inflammatory breast cancer. An SUV cutoff of 2 provided the best accuracy in identifying regional nodal metastasis in this patient population.

Prospective study of 2-[¹⁸F]fluorodeoxyglucose positron emission tomography in the assessment of regional nodal spread of disease in patients with breast cancer: an Ontario clinical oncology group study

PURPOSE

2-[(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET) is potentially useful in assessing lymph nodes and detecting distant metastases in women with primary breast cancer.

PATIENTS AND METHODS

Women diagnosed with operable breast cancer within 3 months underwent FDG-PET at one of five Ontario study centers followed by axillary lymph node assessment (ALNA) consisting of sentinel lymph node biopsy (SLNB) alone if sentinel lymph nodes (SLNs) were negative, SLNB with axillary lymph node dissection (ALND) if SLNB or PET was positive, or ALND alone if SLNs were not identified.

RESULTS

Between January 2005 and March 2007, 325 analyzable women entered this study. Sentinel nodes were found for 312 (96%) of 325 women and were positive for tumor in 90 (29%) of 312. ALND was positive in seven additional women. Using ALNA as the gold standard, sensitivity for PET was 23.7% (95% CI, 15.9% to 33.6%), specificity was 99.6% (95% CI, 97.2% to 99.9%), positive predictive value was 95.8% (95% CI, 76.9% to 99.8%), negative predictive value was 75.4% (95% CI, 70.1% to 80.1%), and prevalence was 29.8% (95% CI, 25.0% to 35.2%). Using logistic regression, tumor size was predictive for prevalence of tumor in the axilla and for PET sensitivity. PET scan was suspicious for distant metastases in 13 patients; three (0.9%) were confirmed as metastatic disease and 10 (3.0%) were false positive.

CONCLUSION

FDG-PET is not sufficiently sensitive to detect positive axillary lymph nodes, nor is it sufficiently specific to appropriately identify distant metastases. However, the very high positive predictive value (96%) suggests that PET when positive is indicative of disease in axillary nodes, which may influence surgical care.

Positron emission tomography (PET) for assessment of axillary lymph node status in early breast cancer: A systematic review and meta-analysis

PURPOSE

Sentinel lymph node biopsy (SLNB) and axillary lymph node dissection (ALND) are used to assess axillary nodal status in breast cancer, but are invasive procedures associated with morbidity, including lymphoedema. This systematic review evaluates the diagnostic accuracy of positron emission tomography (PET), with or without computed tomography (CT), for assessment of axillary nodes in early breast cancer.

METHODS

Eleven databases including MEDLINE, EMBASE and the Cochrane Library, plus research registers and conference proceedings, were searched in April 2009. Study quality was assessed using the QUality Assessment of Diagnostic Accuracy Studies (QUADAS) checklist. Sensitivity and specificity were meta-analysed using a bivariate random effects approach.

RESULTS

Across 26 studies evaluating PET or PET/CT (n = 2591 patients), mean sensitivity was 63% (95% CI: 52-74%; range 20-100%) and mean specificity 94% (95% CI: 91-96%; range 75-100%). Across 7 studies of PET/CT (n = 862), mean sensitivity was 56% (95% CI: 44-67%) and mean specificity 96% (90-99%). Across 19 studies of PET-only (n = 1729), mean sensitivity was 66% (50-79%) and mean specificity 93% (89-96%). Mean sensitivity was 11% (5-22%) for micrometastases (≤2 mm; five studies; n = 63), and 57% (47-66%) for macrometastases (>2 mm; four studies; n = 111).

CONCLUSIONS

PET had lower sensitivity and specificity than SLNB. Therefore, replacing SLNB with PET would avoid the adverse effects of SLNB, but lead to more false negative patients at risk of recurrence and more false positive patients undergoing unnecessary ALND. The present evidence does not support the routine use of PET or PET-CT for the assessment of the clinically negative axilla.

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.

The use of FDG-PET in assessing axillary lymph node status in breast cancer: a systematic review and meta-analysis of the literature

Axillary lymph node status is the most powerful prognostic indicator in patients with breast cancer. FDG-PET has been suggested as a non-invasive method of staging the axilla. The aim of this study was to review and aggregate all studies that measured the performance of FDG-PET in patients with breast cancer, using surgically obtained axillary histology as a reference, in a meta-analysis. A systematic review of the literature was performed and data extracted from all eligible studies. These were then analysed using meta-analysis software and summary receiver operating characteristic (SROC) curves were plotted for the aggregate data. The data was then tested to determine which parameters impacted on the sensitivity and specificity of the studies. Sensitivities ranging from 20 to 100% and specificities ranging from 65 to 100% have been reported. An aggregated ROC analysis found an area under the curve of 0.95 (95% CI 0.91-0.97) and a Q* value of 0.89 (95% CI 0.85-0.92) in a total of 25 studies involving 2,460 patients. The AUC and Q* values indicated little difference between the compared study characteristics. The performance of the technique currently remains below, which is required to replace assessment of axillary node status by surgical biopsy and histological assessment. However, sensitivity and specificity are high and FDG-PET may have a role to play under particular circumstances. Moreover, the additional benefit of an assessment of distal metastatic spread provided by FDG-PET requires further investigation.

The Role of Lymphatic Mapping and Sentinel Lymph Node Biopsy in the Staging of Breast Cancer

The widespread application of sentinel lymph node biopsy in the evaluation of patients with breast cancer has allowed for the more limited, selective treatment of regional lymph nodes and decreased the number of complete regional dissections performed in patients without nodal metastases. Surgical excision and pathologic evaluation of nodes for metastases allow for reliable staging and prediction of additional lymph node metastases. Sentinel lymph node biopsy also enables a meticulous histologic evaluation of multiple sections augmented by immunohistochemical staining. The current role of sentinel lymph node biopsy in the staging of breast cancer and ongoing controversies relating to the procedure are discussed.

Improved breast cancer detection of prone breast fluorodeoxyglucose-PET in 118 patients

OBJECTIVE

To prospectively evaluate the breast cancer detection of prone breast positron emission tomography (PET) images in comparison with supine whole-body PET images.

MATERIAL AND METHODS

One hundred and eighteen female patients (age range 28-91 years) with 122 lesions suspected of having breast cancer underwent fluorine-18 fluorodeoxyglucose PET for preoperative staging. After the whole-body image was acquired, prone breast PET imaging was performed. The findings from both images were compared with the histopathologic results. Sensitivity, specificity, positive predictive value, negative predictive value (NPV), and accuracy were used to compare the diagnostic accuracy of prone breast PET images with that of whole-body PET images.

RESULTS

Sensitivity, specificity, positive predictive value, NPV, and accuracy of whole-body PET images were 83, 50, 97, 17, and 80%, and of prone breast PET images they were 95, 50, 96, 43, and 93%. Ten of 114 breast cancerous lesions (8.8%) were detected on prone breast PET images alone. Statistical difference was found between the sensitivity, accuracy, and NPV of prone breast PET images and those of whole-body PET images (P<0.0001 for sensitivity and accuracy and P<0.0009 for NPV).

CONCLUSION

Our data about the 122 lesions, suspected of breast cancer, with regard to the usefulness of prone breast PET imaging indicate that prone breast PET images are effective in detecting breast cancer.

Breast cancer imaging: a perspective for the next decade

Breast imaging is largely indicated for detection, diagnosis, and clinical management of breast cancer and for evaluation of the integrity of breast implants. In this work, a prospective view of techniques for breast cancer detection and diagnosis is provided based on an assessment of current trends. The potential role of emerging techniques that are under various stages of research and development is also addressed. It appears that the primary imaging tool for breast cancer screening in the next decade will be high-resolution, high-contrast, anatomical x-ray imaging with or without depth information. MRI and ultrasonography will have an increasingly important adjunctive role for imaging high-risk patients and women with dense breasts. Pilot studies with dedicated breast CT have demonstrated high-resolution three-dimensional imaging capabilities, but several technological barriers must be overcome before clinical adoption. Radionuclide based imaging techniques and x-ray imaging with intravenously injected contrast offer substantial potential as a diagnostic tools and for evaluation of suspicious lesions. Developing optical and electromagnetic imaging techniques hold significant potential for physiologic information and they are likely to be of most value when integrated with or adjunctively used with techniques that provide anatomic information. Experimental studies with breast specimens suggest that phase-sensitive x-ray imaging techniques can provide edge enhancement and contrast improvement but more research is needed to evaluate their potential role in clinical breast imaging. From the technological perspective, in addition to improvements within each modality, there is likely to be a trend towards multi-modality systems that combine anatomic with physiologic information. We are also likely to transition from a standardized screening, where all women undergo the same imaging exam (mammography), to selection of a screening modality or modalities based an individual-risk or other classification.

Regulation of the Warburg effect in early-passage breast cancer cells

Malignancy in cancer is associated with aerobic glycolysis (Warburg effect) evidenced by increased trapping of [(18)F]deoxyglucose (FdG) in patients imaged by positron emission tomography (PET). [(18)F]deoxyglucose uptake correlates with glucose transporter (GLUT-1) expression, which can be regulated by hypoxia-inducible factor 1 alpha (HIF-1alpha). We have previously reported in established breast lines that HIF-1alpha levels in the presence of oxygen leads to the Warburg effect. However, glycolysis and GLUT-1 can also be induced independent of HIF-1alpha by other factors, such as c-Myc and phosphorylated Akt (pAkt). This study investigates HIF-1alpha, c-Myc, pAkt, and aerobic glycolysis in low-passage breast cancer cells under the assumption that these represent the in vivo condition better than established lines. Similar to in vivo FdG-PET or primary breast cancers, rates of glycolysis were diverse, being higher in cells expressing both c-Myc and HIF-1alpha and lower in cell lines low or negative in both transcription factors. No correlations were observed between glycolytic rates and pAkt levels. Two of 12 cell lines formed xenografts in mice. Both were positive for HIF-1alpha and phosphorylated c-Myc, and only one was positive for pAkt. Glycolysis was affected by pharmacological regulation of c-Myc and HIF-1alpha. These findings suggest that c-Myc and/or HIF-1alpha activities are both involved in the regulation of glycolysis in breast cancers.

Is there a role for positron emission tomography in breast cancer staging?

Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) is a radiotracer imaging method that is used in the care of patients with cancer. We conducted a nonsystematic review of the literature regarding the applicability of this technique in patients with breast cancer, encompassing the impact of FDG-PET on surgical management, including axillary node staging and sentinel lymph node biopsy; the use of FDG-PET in the evaluation of the primary tumor; the role of FDG-PET in the evaluation of distant metastases both at diagnosis and in the investigation of suspected recurrence; and the ability of FDG-PET to predict treatment response. FDG-PET is not sufficiently sensitive to replace histologic surgical staging of the axilla. Although FDG avidity of the primary tumor has been shown to be an unfavorable indicator, there is insufficient information to recommend its routine use for this indication. FDG-PET is more sensitive than conventional imaging in the detection of metastatic or recurrent disease, but the impact of increased sensitivity on patient care and outcome has not been demonstrated. The data regarding prediction of treatment response are insufficient to reach any conclusion. There are a number of prospective, adequately powered clinical trials currently in progress that should provide more definitive answers regarding the role, if any, of this technique in the management of patients with breast cancer.

ACR Appropriateness Criteria® on Palpable Breast Masses

Palpable breast masses may become evident during breast self-examination or clinical breast examination or retrospectively after screening mammography. Because most breast masses do not exhibit distinctive physical findings, imaging evaluation is almost always necessary to characterize the lesions and screen the reminder of both breasts. Depending on age, the primary imaging evaluation of a palpable breast mass is mammography or breast ultrasound. Negative imaging results should not deter the biopsy of a clinically suspicious breast mass.

FDG PET positive lymph nodes are highly predictive of metastasis in breast cancer

AIM

To determine whether or not fluorodeoxyglucose positron emission tomography (FDG PET) imaging when positive could obviate the necessity for sentinel lymph node biopsy and for complete axillary node dissection in patients with breast cancer.

METHODS

A total of 80 female patients with a histological diagnosis of breast cancer and clinically negative axillary nodes underwent an FDG PET and sentinel lymph node biopsy (SLNB) or total axillary dissection for staging of axilla. Both SLNB and axillary dissection were performed in 72 patients, while eight patients had total axillary dissection without SLN biopsy.

RESULTS

Of the 80 patients, 36 had lymph node metastasis on histopathology. SLNB was positive for metastasis in 35 (97%) of 36 patients (29 macrometastasis and seven micrometastasis). In the patient with false negative SLNB, the lymph node was completely replaced by the tumour. The FDG PET was true positive in 16 of 36 patients (sensitivity, 44%). There were two false positive studies with FDG PET, resulting in a specificity of 95%. The positive predictive value and accuracy of FDG PET for the detection of axillary lymph node metastasis were 89% and 72%, respectively. Univariate analysis revealed that higher grade of tumour, increased size and number of axillary lymph nodes were significantly associated with positive FDG PET results for axillary staging.

CONCLUSION

FDG PET cannot replace histological staging using SLNB in patients with breast cancer. However, FDG PET has a high specificity and positive predictive value for staging of the axilla in these patients. The patients with higher grade of tumour, larger size and higher number of axillary lymph nodes may be considered for FDG PET scan for axillary staging.

[Contribution of positron emission tomography to the detection and staging of breast cancer]

INTRODUCTION

18F-fluorodeoxyglucose positron emission tomography (FDG-PET) is a diagnostic imaging tool with multiple applications in oncology. One of the more promising applications in breast cancer is noninvasive lymph node staging and detection of distant metastases, which may provide useful information about prognosis and treatment response.

MATERIAL AND METHOD

Published studies on FDG-PET applications in breast cancer detection and staging were reviewed. We also present our own experience in patients referred for preoperative staging of breast cancer.

RESULTS

FDG-PET is very useful in evaluating dense breasts, multicentric disease and breast prostheses. The sensitivity of FDG-PET for nodal staging is low, and consequently it cannot replace either sentinel lymph node biopsy or histologic examination. However, it is more accurate than another noninvasive techniques and is very useful in internal mammary node chain evaluation. FDG-PET can improve and maybe replace conventional imaging in detecting metastatic disease, especially in high risk patients with locoregionally advanced recurrent breast cancer or increased serum tumor markers, and helps to characterize unclear findings of anatomic imaging techniques or scintigraphy.

CONCLUSIONS

FDG-PET is useful in breast cancer staging. It complements and even improves information from other diagnostic techniques and changes therapeutic management in a high proportion of patients.

Planar Tc99m--sestamibi scintimammography should be considered cautiously in the axillary evaluation of breast cancer protocols: results of an international multicenter trial

Background

Lymph node status is the most important prognostic indicator in breast cancer in recently diagnosed primary lesion. As a part of an interregional protocol using scintimammography with Tc99m compounds, the value of planar Tc99m sestamibi scanning for axillary lymph node evaluation is presented. Since there is a wide range of reported values, a standardized protocol of planar imaging was performed.

Methods

One hundred and forty-nine female patients were included prospectively from different regions. Their mean age was 55.1 ± 11.9 years. Histological report was obtained from 2.987 excised lymph nodes from 150 axillas. An early planar chest image was obtained at 10 min in all patients and a delayed one in 95 patients, all images performed with 740–925 MBq dose of Tc99m sestamibi. Blind lecture of all axillary regions was interpreted by 2 independent observers considering any well defined focal area of increased uptake as an involved axilla. Diagnostic values, 95% confidence intervals [CI] and also likelihood ratios (LR) were calculated.

Results

Node histology demonstrated tumor involvement in 546 out of 2987 lymph nodes. Sestamibi was positive in 30 axillas (25 true-positive) and negative in 120 (only 55 true-negative). The sensitivity corresponded to 27.8% [CI = 18.9–38.2] and specificity to 91.7% [81.6–97.2]. The positive and negative LR were 3.33 and 0.79, respectively. There was no difference between early and delayed images. Sensitivity was higher in patients with palpable lesions.

Conclusion

This work confirmed that non tomographic Tc99m sestamibi scintimammography had a very low detection rate for axillary lymph node involvement and it should not be applied for clinical assessment of breast cancer.

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.

Fluorodeoxyglucose-PET in the management of breast cancer

FDG-PET can be helpful in the diagnosis of primary breast cancer, especially in patients with dense breast tissue, significant fibrocystic changes, fibrosis after radiotherapy, and inconclusive results from MR imaging and other imaging modalities. PET has a limited role in patients with very small tumors and with well-differentiated and lobular types of breast cancer. In preoperative staging, FDG-PET has a low sensitivity for detection of regional lymph node involvement. Also, current PET imaging techniques can easily miss micrometastases. FDG-PET, however, has high positive predictive value for the axillary lymph node involvement, especially patient with advanced tumors. Compared with conventional imaging modalities, FDG-PET provides high diagnostic accuracy in detecting recurrent or metastatic breast carcinoma. FDG-PET seems to be highly useful for monitoring response to therapeutic interventions. This technique can identify response to therapy earlier than any other imaging method currently available. Obviously, identification of nonresponding patients could greatly improve patient management by allowing termination of ineffective and toxic therapies.

99mTc glucarate high-resolution imaging of drug sensitive and drug resistant human breast cancer xenografts in SCID mice

BACKGROUND AND AIM

Previous studies have showed that 99mTc labelled glucarate (GLA) might be an agent for non-invasive detection of breast tumours. In xenografted BT20 breast tumours, GLA was found to have higher uptake than 99mTc sestamibi (MIBI). It is unclear whether GLA can localize in all cell line breast cancer xenografts, as well as breast tumours with multidrug resistance (MDR). The present study aimed to investigate the properties of GLA in detecting drug sensitive and drug resistant MCF7 breast cancer xenografts in mice by using dynamic single photon emission computed tomography (SPECT) imaging.

METHODS

MCF7/S cells are drug sensitive breast carcinoma cells. MCF7/D40 cells are 40-fold more resistant to doxorubicin compared to MCF7/S. Subcutaneous tumours were grown in SCID mice for 10-14 days after injection of 1 x 10(6) cells into the right thigh. Anaesthetized mice with MCF7/S (MIBI, n=9; GLA, n=8) and MCF7/D40 (MIBI, n=6; GLA, n=5) tumours were imaged using a high-resolution SPECT system called FASTSPECT. Dynamic images were acquired for 2 h after intravenous injection of GLA or MIBI. Expression of MDR P-glycoprotein (Pgp) in the tumours was demonstrated in the MCF7/D40 tumours by western blotting, not in the MCF7/S tumours.

RESULTS

The xenografted tumours were visualized unequivocally within 10-30 min in GLA images and remained detectable for at least 2 h after injection. Drug resistant tumours, from which MIBI was rapidly expelled, retained GLA as readily as did drug sensitive tumours. The biodistribution data of GLA demonstrated significantly higher accumulation (%ID/g) compared to MIBI.

CONCLUSION

MCF7 tumour xenografts can be detected by 99mTc glucarate imaging. More importantly, 99mTc glucarate can potentially localize drug resistant breast tumours.

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."

Partial breast irradiation with interstitial 60CO brachytherapy results in frequent grade 3 or 4 toxicity. evidence based on a 12-year follow-up of 70 patients

PURPOSE

To investigate the radiation-induced toxicity and cosmesis of brachytherapy (BT) alone in early stage breast cancer.

METHODS AND MATERIALS

A total of 70 women diagnosed with Stage I or II breast carcinoma participated in a BT study at the Municipal Oncoradiological Center, Uzsoki Hospital, Budapest, Hungary, between November 1987 and June 1992. They had undergone breast-conserving surgery with an unknown surgical margin. The postoperative tumor bed irradiation was performed with interstitial (60)Co sources with an active length of 4 cm, with 10-mm center-to-center spacing arranged in a single plane. The median number of inserted sources was 5 (range, 2-8), with a linear activity of 133-137 MBq/cm at the beginning of the study. The 50 Gy delivered dose at 5 mm from the surface of the (60)Co sources was administered during 10-22 h to the virtual postoperative lumpectomy cavity (i.e., plane). For radiobiologic considerations, the clinical target volume (CTV) was calculated retrospectively with a 10-mm safety margin, resulting in a 72-cm(3) median CTV (range, 36-108 cm(3)) irradiated with a reference dose of 28 Gy. In the assessment of the skin and subcutaneous toxicity, the RTOG late radiation morbidity scoring system was applied. The radiosensitivity of the cultured fibroblasts was determined by clonogenic assay to check whether individual radiosensitivity played a role in the development and course of radiation-induced side-effects.

RESULTS

The median follow-up was 12 years (range, 10-15 years). The population of the final study (34 cases) comprised all survivors with tumor-free breasts (27 cases) and patients with breasts erroneously ablated/excised for misinterpreted radiation-induced sequelae (7 patients). A total of 97% of the cohort (33/34) had grade > or =2, and 59% (20/34) had grade > or =3 radiation-induced toxicity. By the end of the follow-up, 85% of the patients experienced Grade > or =2 telangiectasis and 41% had Grade 3 telangiectasis. Eighty-eight percent had fibrosis of some form, and 35% had grade > or =3 fibrosis. Forty-one percent of the cohort displayed fat necrosis, which was always accompanied by Grade > or =3 fibrosis or telangiectasis. The cosmetic results were poor in 50% (17/34) of the patients. The radiosensitivity of the fibroblasts was increased in only 2/24 patients (8% of the investigated cases, in agreement with data published for the general population). Comparisons of our fibrosis prevalence data with those of others allowed an estimate of 0.47 h(-1) for the rate of recovery of DNA damage in the fibroblasts.

CONCLUSIONS

Interstitial (60)Co BT of the breast tumor bed alone with a limited CTV (median, 72 cm(3)) and a total dose of 28 Gy is associated with a high rate (59%) of grade > or =3 radiation-induced toxicity and a high rate (50%) of poor cosmetic outcome at the end of a median follow-up of 12 years. A relatively high BT dose rate (1.3-2.8 Gy/h) applied during a short overall treatment time (10-22 h) and a possible geographic miss (close to skin implantation) might have contributed to the development of these sequelae.

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.

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

Imaging with 99mTc ECDG targeted at the multifunctional glucose transport system: feasibility study with rodents

PURPOSE

To evaluate the feasibility of technetium 99m ((99m)Tc) ethylenedicysteine-deoxyglucose (ECDG) imaging in tumor-bearing rodents.

MATERIALS AND METHODS

ECDG was synthesized by means of reacting ethylenedicysteine with glucosamine, with carbodiimide as the coupling agent. Hexokinase assays were performed at an ultraviolet wavelength of 340 nm. To determine whether blood glucose level could be altered, ECDG or glucosamine was injected into six rats. In a separate study, ECDG followed by insulin was administered to three rats. To determine biodistribution, lung tumor cells were intramuscularly injected into the hind legs of 18 nude mice. The animals were then injected with (99m)Tc ECDG or fluorine 18 ((18)F) fluorodeoxyglucose (FDG) (0.037-0.074 MBq per mouse). Radioactivity was measured in tissue excised from the animals. Scintigraphy was performed in three groups: in group 1 to demonstrate that different-sized tumors could be imaged after (99m)Tc ECDG administration, in group 2 to ascertain whether tumor uptake of (99m)Tc ECDG was perfusion related, and in group 3 to demonstrate that tumor uptake of (99m)Tc ECDG occurred by means of a glucose-mediated process.

RESULTS

ECDG was positive for phosphorylation at hexokinase assay. Blood glucose level increased with ECDG injection and decreased with insulin administration. Tumor-to-brain tissue and tumor-to-muscle tissue ratios of (99m)Tc ECDG uptake were higher than those of (18)F FDG uptake. Scintigraphic results demonstrated the feasibility of (99m)Tc ECDG imaging.

CONCLUSION

There are similarities between (99m)Tc ECDG uptake and (18)F FDG uptake in tumors, and study findings supported the potential use of (99m)Tc ECDG as a functional imaging agent.

Comparison of FDG-PET and dynamic contrast-enhanced MRI in the evaluation of suggestive breast lesions

The aim of our study was a direct comparison of the ability of positron-emission tomography with FDG-PET and of magnetic resonance imaging (MRI) to determine whether breast lesions were benign or malignant and of the two imaging methods capability of depicting eventual multifocal disease. We performed both PET and MRI in 36 patients (40 lesions) who were scheduled for surgery because of suggestive mammographic, sonographic and/or clinical findings. A final histological classification was available for all lesions. Tumour size ranged from 5 to 45 mm (mean 16.7 mm). Sensitivity for lesions, sensitivity for patients, specificity for lesions and specificity for patients were 68.0%, 76.2%, 73.3%, and 73.3% for PET and 92.0%, 95.2%, 73.3%, and 73.3% for MRI, respectively. MRI was more sensitive than FDG-PET in disclosing malignant breast tumours and was also more accurate than FDG-PET in the assessment of multifocal disease. The lower sensitivity of FDG-PET than of MRI seems to be due to difficulties in reliable imaging of carcinomas smaller than 10 mm and of lobular carcinomas.

Determinants of diagnostic performance of [F-18]fluorodeoxyglucose positron emission tomography for axillary staging in breast cancer

OBJECTIVE

To prospectively investigate determinants of the accuracy of staging axillary lymph nodes in breast cancer using [F-18]fluorodeoxyglucose positron emission tomography (FDG PET).

METHODS

Patients with primary operable breast cancer underwent FDG PET of the chest followed by sentinel node biopsy (SNB, n = 47) and/or complete axillary lymph node dissection (ALND, n = 23). PET scans were independently interpreted by three observers in a blinded fashion with respect to the FDG avidity of the primary tumor and the axillary status. The results were compared to histopathological analyses of the axillary lymph nodes. Clinicians were blinded to the PET results.

RESULTS

Axillary lymph node specimens and FDG PET scans were evaluated in 70 patients (59% cT1). Overall, 32 (46%) had lymph node metastases as established by SNB (18/47) or ALND (14/23), 20 of which were confined to a single node. The overall sensitivity of FDG PET was 25%, with a specificity of 97%. PET results were false-negative in all 18 positive SNBs and true-positive in 8/14 in the ALND group. The performance of FDG PET depended on the axillary tumor load and the FDG avidity of the primary tumor. Intense uptake in the primary tumor was found in only 57% of the patients, and this was independent of the size. There was excellent interobserver agreement of visual assessment of FDG uptake in primary tumor and axillary lymph nodes.

CONCLUSIONS

The sensitivity of FDG PET to detect occult axillary metastases in operable breast cancer was low, and it was a function of axillary tumor load and FDG avidity of the primary tumor. Even though the clinical relevance of occult disease detected by SNB needs to be confirmed, it is suggested that FDG PET in these patients should be focused on exploiting its nearly perfect specificity and the potential prognostic relevance of variable FDG uptake.

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.

Contribution by different fuels and metabolic pathways to the total ATP turnover of proliferating MCF-7 breast cancer cells

For the past 70 years the dominant perception of cancer metabolism has been that it is fuelled mainly by glucose (via aerobic glycolysis) and glutamine. Consequently, investigations into the diagnosis, treatment and the basic metabolism of cancer cells have been directed by this perception. However, the data on cancer metabolism are equivocal, and in this study we have sought to clarify the issue. Using an innovative system we have measured the total ATP turnover of the MCF-7 breast cancer cell line, the contributions to this turnover by oxidative and glycolytic ATP production and the contributions to the oxidative component by glucose, lactate, glutamine, palmitate and oleate. The total ATP turnover over approx. 5 days was 26.8 micromol of ATP.10(7) cells(-1).h(-1). ATP production was 80% oxidative and 20% glycolytic. Contributions to the oxidative component were approx. 10% glucose, 14% glutamine, 7% palmitate, 4% oleate and 65% from unidentified sources. The contribution by glucose (glycolysis and oxidation) to total ATP turnover was 28.8%, glutamine contributed 10.7% and glucose and glutamine combined contributed 40%. Glucose and glutamine are significant fuels, but they account for less than half of the total ATP turnover. The contribution of aerobic glycolysis is not different from that in a variety of other non-transformed cell types.

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.

Dedicated breast CT: radiation dose and image quality evaluation

PURPOSE

To evaluate the feasibility of breast computed tomography (CT) in terms of radiation dose and image quality.

MATERIALS AND METHODS

Validated Monte Carlo simulation techniques were used to estimate the average glandular dose (AGD). The calculated photon fluence at the detector for high-quality abdominal CT (120 kVp, 300 mAs, 5-mm section thickness) was the benchmark for assessing the milliampere seconds and corresponding radiation dose necessary for breast CT. Image noise was measured by using a 10-cm-diameter cylinder imaged with a clinical CT scanner at 10-300 mAs for 80, 100, and 120 kVp. A cadaveric breast was imaged in the coronal plane to approximate the acquisition geometry of a proposed breast CT scanner.

RESULTS

The AGD for 80-kVp breast CT was comparable to that for two-view mammography of 5-cm breasts (compressed breast thickness). For thicker breasts, the breast CT dose was about one-third less than that for two-view mammography. The maximum dose at mammography assessed in 1-mm(3) voxels was far higher (20.0 mGy) than that at breast CT (5.4 mGy) for a typical 5-cm 50% glandular breast. CT images of an 8-cm cadaveric breast (AGD, 6.3 mGy) were subjectively superior to digital mammograms (AGD, 10.1 mGy) of the same specimen.

CONCLUSION

The potential of high signal-to-noise ratio images with low anatomic noise, which are obtainable at dose levels comparable to those for mammography, suggests that dedicated breast CT should be studied further for its potential in breast cancer screening and diagnosis.

[(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.

The role of 99m Tc-sestamibi scintimammography and colour Doppler ultrasonography in the evaluation of breast lesions

In the present study we evaluated comparatively the diagnostic value of mammography, of 99mTc-sestamibi scintimammography (sestamibi-SC) and of colour Doppler ultrasonography (CD-US) in 116 breast lesions. Diagnosis was based on histopathological examination. Overall, out of 86 malignant tumours, 80 (93%) and 75 (87%) had a positive sestamibi-SC and positive CD-US, respectively. Out of 30 benign lesions, 25 (83%) and 26 (87%) had a negative sestamibi-SC and negative CD-US respectively. The true positive results were similar in palpable and in non-palpable lesions for both methods. Out of 19 non-palpable malignant tumours, mammography confirmed malignancy in only one case (5%), which was significantly lower than the results obtained by sestamibi-SC (89%; Px0.0001) and by CD-US (74%; P=0.0001). In palpable malignant tumours, by using mamography, true positive results were obtained in 54/67 (80.5%) patients, which was significantly lower than the results obtained by sestamibi-SC (94%; P=0.03) and marginally different to the results obtained by CD-US (91%; P=0.13). It is concluded that sestamibi-SC and CD-US are useful tools in clarifying the nature of breast lesions in cases with doubtful mammography. The clinical value of these diagnostic procedures in guiding subsequent therapeutic interventions requires further investigation.

Current status of PET in breast cancer imaging, staging, and therapy

The exact roles of PET in the imaging management of patients with known or suspected breast cancer are still in evolution. For assessing primary lesions, it is sometimes possible with PET to detect cancers occult on standard methods. This could be useful in high-risk patient populations, but in dense breasts, background FDG uptake is often higher than in women with fatty breasts, making identification of lesions < 1 cm in size improbable with current technologies. Distinguishing malignant from benign primary breast disease would seem better addressed by biopsy. With a positive predictive value of FDG PET for cancer over 96%, any FDG-avid breast lesion is highly suspicious and merits biopsy. Although PET in theory should be useful for depicting multifocal disease before surgery, the limitations in detecting small lesions in the breast limit the contribution of PET at present. It is most likely that PET will have a greater role in depicting primary breast lesions as dedicated PET imaging devices for the breast evolve. For axillary and internal mammary nodal staging, results with FDG PET are variable. Small nodal metastases < or = 5 mm will be missed by PET, whereas larger ones are more likely to be detected. PET can depict internal mammary nodes, but the accuracy of the method in this setting is not known, nor is there consensus on how identifying internal mammary node metastases will change treatment. Based on the available data, for pT1 breast lesions, PET, if negative, is not an adequate replacement for sentinel node surgery or axillary dissection. Results from the multicenter trial will be of great interest. Clearly PET can stage metastatic disease well. Bone scans with 18F- are exquisitely sensitive for metastases, and FDG is also very good. However, FDG PET can miss some blastic metastases to bone so at present FDG is not capable of excluding the presence of bone metastases. PET seems very well suited to detecting recurrences in soft tissues and the brachial plexus region in particular. The utility of PET in planning the treatment of individual patients appears promising. Although results must be confirmed in larger studies, it appears safe to conclude that failure of a chemotherapy regimen to decrease FDG uptake promptly in a breast cancer portends poor response. This does not hold true for hormonal therapy. At present, labeled estrogens are not widely available and cannot be recommended for clinical use. Thus, PET has shown considerable promise in breast cancer imaging, but in the author's experience is best applied to solve difficult imaging questions in specific patients and is not recommended for routine evaluation of the breast cancer patient. However, in larger primary tumors, the ability to use PET for staging and to plan treatment response suggest it will be more widely used. Additional studies with newer PET imaging devices and FDG and other tracers will help us better determine the role of PET in routine clinical care of the patient with known or suspected breast cancer. Certainly, this represent a fertile area for translational research studies over the next several years with the potential to significantly alter the way breast cancer is imaged and managed.