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

Development of a mechatronic guidance system for targeted ultrasound-guided biopsy under high-resolution positron emission mammography localization

PURPOSE

Image-guided needle biopsy of small, detectable lesions is crucial for early-stage diagnosis, treatment planning, and management of breast cancer. High-resolution positron emission mammography (PEM) is a dedicated functional imaging modality that can detect breast cancer independent of breast tissue density, but anatomical context and real-time needle visualization are not yet available to guide biopsy. We propose a mechatronic guidance system integrating an ultrasound (US)-guided core-needle biopsy (CNB) with high-resolution PEM localization to improve the spatial sampling of breast lesions. This paper presents the benchtop testing and phantom studies to evaluate the accuracy of the system and its constituent components for targeted PEM-US-guided biopsy under simulated high-resolution PEM localization.

METHODS

A mechatronic guidance system was developed to operate with the Radialis PEM system and a conventional US system. The system includes a user-operated guidance arm and end-effector biopsy device, integrating a US transducer and CNB gun, with its needle focused on a remote center of motion (RCM). Custom software modules were developed to track, display, and guide the end-effector biopsy device. Registration of the mechatronic guidance system to a simulated PEM detector plate was performed using a landmark-based method. Testing was performed with fiducials positioned in the peripheral and central regions of the simulated detector plate and registration error was quantified. Breast phantom experiments were performed under ideal detection and localization to evaluate for bias in the end-effector biopsy device. The accuracy of the complete mechatronic guidance system to perform targeted breast biopsy was assessed using breast phantoms with simulated lesions. Three-dimensional positioning error was quantified, and principal component analysis assessed for directional trends in 3D space within 95% prediction intervals. Targeted breast biopsies with test phantoms were performed and an overall in-plane needle targeting error was quantified.

RESULTS

The mean registration errors were 0.63 mm (N = 44) and 0.73 mm (N = 72) in the peripheral and central regions of the simulated PEM detector plate, respectively. A 3D 95% prediction ellipsoid shows an error volume <2.0 mm in diameter, centered on the mean registration error. Under ideal detection and localization, targets <1.0 mm in diameter can be sampled with 95% confidence. The complete mechatronic guidance system was able to successfully spatially sample simulated breast lesions, 4 mm and 6 mm in diameter and height (N = 20) in known 3D positions in the PEM image coordinate space. The 3D positioning error was 0.85 mm (N = 20) with 0.64 mm in-plane and 0.44 mm cross-plane component errors. Targeted breast biopsies resulted in a mean in-plane needle targeting error of 1.08 mm (N = 15) allowing for targets 1.32 mm in radius to be sampled with 95% confidence.

CONCLUSIONS

We demonstrated the utility of our mechatronic guidance system for targeted breast biopsy under high-resolution PEM localization. Breast phantom studies showed the ability to accurately guide, position, and target breast lesions with the accuracy to spatially sample targets <3.0 mm in diameter with 95% confidence. Future work will integrate the developed system with the Radialis PEM system toward combined PEM-US-guided breast biopsy.

Progress and Future Trends in PET/CT and PET/MRI Molecular Imaging Approaches for Breast Cancer

Breast cancer is a major disease with high morbidity and mortality in women worldwide. Increased use of imaging biomarkers has been shown to add more information with clinical utility in the detection and evaluation of breast cancer. To date, numerous studies related to PET-based imaging in breast cancer have been published. Here, we review available studies on the clinical utility of different PET-based molecular imaging methods in breast cancer diagnosis, staging, distant-metastasis detection, therapeutic and prognostic prediction, and evaluation of therapeutic responses. For primary breast cancer, PET/MRI performed similarly to MRI but better than PET/CT. PET/CT and PET/MRI both have higher sensitivity than MRI in the detection of axillary and extra-axillary nodal metastases. For distant metastases, PET/CT has better performance in the detection of lung metastasis, while PET/MRI performs better in the liver and bone. Additionally, PET/CT is superior in terms of monitoring local recurrence. The progress in novel radiotracers and PET radiomics presents opportunities to reclassify tumors by combining their fine anatomical features with molecular characteristics and develop a beneficial pathway from bench to bedside to predict the treatment response and prognosis of breast cancer. However, further investigation is still needed before application of these modalities in clinical practice. In conclusion, PET-based imaging is not suitable for early-stage breast cancer, but it adds value in identifying regional nodal disease and distant metastases as an adjuvant to standard diagnostic imaging. Recent advances in imaging techniques would further widen the comprehensive and convergent applications of PET approaches in the clinical management of breast cancer.

PET Imaging of 18F-(2 S,4 R)4-Fluoroglutamine Accumulation in Breast Cancer: From Xenografts to Patients

Sustaining the growth of tumor cells requires extra energy and metabolic building blocks. In addition to consuming glucose, glutamine may play the role as an alternative source of nutrient for growth and survival. We aim to characterize a glutamine analog, ¹⁸F-(2 S,4 R)4-fluoroglutamine (¹⁸F-(2 S,4 R)4-FGln), as an imaging agent for interrogating the role of glutamine from the in vitro study of tumor cells to clinical manifestation in breast cancer patients. Purity was measured by radio-high-performance liquid chromatography (radio-HPLC), and the stability after production was evaluated in phosphate buffer saline (PBS), saline, and mouse and human serum buffers. The presence of Myc expression in MCF-7 and U87 cells was conducted using qPCR. In vitro cell uptake of ¹⁸F-(2 S,4 R)4-FGln in MCF-7 and U87 cells was directly compared with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG). In vivo biodistribution and micro-PET imaging of ¹⁸F-(2 S,4 R)4-FGln in MCF-7 bearing BALB/c nude mice were performed. PET/CT imaging of ¹⁸F-(2 S,4 R)4-FGln was compared with ¹⁸F-FDG in the same group of breast cancer patients ( n = 10). We successfully synthesized ¹⁸F-(2 S,4 R)4-FGln with a high radiochemical purity (>98%), and the radiochemical purity was unchanged in PBS and saline buffers during a 2 h incubation. In vitro cell uptake studies of ¹⁸F-(2 S,4 R)4-FGln displayed a rapid and higher uptake in MCF-7 and U87 cells as compared with ¹⁸F-FDG. Biodistribution and micro-PET images showed excellent tumor accumulation of ¹⁸F-(2 S,4 R)4-FGln in the MCF-7-implanted mice tumor model. In a preliminary clinical study, ¹⁸F-(2 S,4 R)4-FGln/PET detected more lesions in breast cancer patients than ¹⁸F-FDG/PET (90% vs 80%). Additionally, in one patient with breast lobular carcinoma, there was a lesion mean standardized uptake value (SUV_mean) and maximum standardized uptake value (SUV_max) for ¹⁸F-(2 S,4 R)4-FGln higher than those obtained by ¹⁸F-FDG, as determined by PET imaging. ¹⁸F-(2 S,4 R)4-FGln may be a useful glutamine-targeting metabolic probe for noninvasive imaging of breast cancer.

The RUNX2 Transcription Factor Negatively Regulates SIRT6 Expression to Alter Glucose Metabolism in Breast Cancer Cells

Activation of genes promoting aerobic glycolysis and suppression of mitochondrial oxidative phosphorylation is one of the hallmarks of cancer. The RUNX2 transcription factor mediates breast cancer (BC) metastasis to bone and is regulated by glucose availability. But, the mechanisms by which it regulates glucose metabolism and promotes an oncogenic phenotype are not known. RUNX2 expression in luminal BC cells correlated with lower estrogen receptor-α (ERα) levels, anchorage-independent growth, expression of glycolytic genes, increased glucose uptake, and sensitivity to glucose starvation, but not to inhibitors of oxidative phosphorylation. Conversely, RUNX2 knockdown in triple-negative BC cells inhibited mammosphere formation and glucose dependence. RUNX2 knockdown resulted in lower LDHA, HK2, and GLUT1 glycolytic gene expression, but upregulation of pyruvate dehydrogenase-A1 (PDHA1) mRNA and enzymatic activity, which was consistent with lower glycolytic potential. The NAD-dependent histone deacetylase, SIRT6, a known tumor suppressor, was a critical regulator of these RUNX2-mediated metabolic changes. RUNX2 expression resulted in elevated pAkt, HK2, and PDHK1 glycolytic protein levels that were reduced by ectopic expression of SIRT6. RUNX2 also repressed mitochondrial oxygen consumption rates (OCR), a measure of oxidative phosphorylation (respiration). Overexpression of SIRT6 increased respiration in RUNX2-positive cells, but knockdown of SIRT6 in cells expressing low RUNX2 decreased respiration. RUNX2 repressed SIRT6 expression at both the transcriptional and post-translational levels and endogenous SIRT6 expression was lower in malignant BC tissues or cell lines that expressed high levels of RUNX2. These results support a hypothesis whereby RUNX2-mediated repression of the SIRT6 tumor suppressor regulates metabolic pathways that promote BC progression.

Increase in Distant Stage Breast Cancer Incidence Rates in US Women Aged 25-49 Years, 2000-2011: The Stage Migration Hypothesis

Background. Unexplained increases have been reported in incidence rates for breast cancer diagnosed at distant stage in younger U.S. women, using data from the Surveillance, Epidemiology and End Results (SEER) Program. Methods. This report focused on recent SEER trends (2000–2011) in age-standardized incidence rates of invasive breast cancer at ages 25–39 and 40–49 years and the hypothesis that stage migration may have resulted from advances in detecting distant metastases at diagnosis. Results. Increases in the rates for distant stage were roughly equal to decreases in the rates for the most advanced stage subgroups within regional stage; this was evident for estrogen receptor (ER) negative cancers, associated with poorer prognosis, but not for ER positive cancers. The 3-year relative survival rate increased over time for distant stage (especially in the ER positive subgroup) and regional stage but not for localized stage; these trends do not contradict the stage-migration hypothesis. Conclusions. Findings provide some support for stage migration as one explanation for the recent increase in incidence of distant stage breast cancer, but additional studies are needed using other databases.

Intrinsically radiolabeled nanoparticles: an emerging paradigm

Although chelator-based radiolabeling techniques have been used for decades, concerns about the complexity of coordination chemistry, possible altering of pharmacokinetics of carriers, and potential detachment of radioisotopes during imaging have driven the need for developing a simple yet better technique for future radiolabeling. Here, the emerging concept of intrinsically radiolabeled nanoparticles, which could be synthesized using methods such as hot-plus-cold precursors, specific trapping, cation exchange, and proton beam activation, is introduced. Representative examples of using these multifunctional nanoparticles for multimodality molecular imaging are highlighted together with current challenges and future research directions. Although still in the early stages, design and synthesis of intrinsically radiolabeled nanoparticles has shown attractive potential to offer easier, faster, and more specific radiolabeling possibilities for the next generation of molecular imaging.

Role of ¹⁸F-FDG PET CT as an independent prognostic indicator in patients with hepatocellular carcinoma

OBJECTIVES

The aim of the study was to evaluate the role of F-fluorodeoxyglucose PET computed tomography (F-FDG PET CT) as an independent prognostic indicator in patients with hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

PET contrast-enhanced CT scans of 100 consecutive patients with HCC were reviewed retrospectively. Patients were asked to fast for 6 h before the study and blood glucose levels were monitored and ensured to be less than 200 mg/dl before injection of F-FDG. After administering the F-FDG injection (370-550 MBq) patients were instructed to rest comfortably for 45-60 min. All images were acquired using a dedicated GE Discovery PET/CT scanner. The PET CT scans of all the patients were reported separately by two nuclear medicine physicians. A stage-wise analysis of the compiled data was carried out. Lesions that showed standardized uptake values greater than background activity (activity in adjacent normal liver tissue) were defined as having increased F-FDG uptake. Pearson's χ -test or the Kruskal-Wallis test was used to assess statistical significance. A P value less than 0.05 was taken as significant.

RESULTS

In this retrospective study of 100 HCC patients, a radiologically higher-stage disease was found more commonly in patients with F-FDG-avid primary tumors (P<0.001), whereas a lower-stage disease was found in patients with non-F-FDG-avid primary tumors. The non-F-FDG-avid tumors also showed lower incidence of metastatic disease and portal vein thrombosis (P<0.001). The histopathological findings of the patients who underwent liver transplantation demonstrated that a higher-grade tumor was more common in the F-FDG-avid tumor group than in the non-F-FDG-avid tumor group (P<0.05).

CONCLUSION

An F-FDG PET CT scan can be used not only for staging but also as a tool for preoperative prediction of cellular differentiation in patients with HCC. The F-FDG uptake seen on a PET scan can serve as a molecular signature for management decisions and can be used as an independent and significant prognostic factor in patients with HCC.

First-line chemotherapy with liposomal doxorubicin plus cyclofosfamide in metastatic breast cancer: a case report of early and prolonged response

The treatment choice for metastatic breast cancer should consider the appropriate balance between efficacy and toxicity of the therapy. We discuss a clinical case with an early response and prolonged to liposomal anthracyclines-based chemotherapy, without cardiotoxicity, enhancing the evidence of safety of liposomal formulation to prevent heart damage. Moreover, the case seems to be of interest for the role of 18F-FDG-PET in clinical response assessment: an early decrease of the standardized uptake value value, even before conventional imaging evaluation, is highly predictive for prolonged clinical response.

False Positive 18F-FDG Uptake in Mediastinal Lymph Nodes Detected with Positron Emission Tomography in Breast Cancer: A Case Report

Breast cancer is the most frequently diagnosed cancer among females. It is accepted that lymph node involvement with metastatic tumor and the presence of distant metastasis are the most important prognostic factors. Accurate staging is important in determining prognosis and appropriate treatment. Positron emission tomography with computed tomography detects malignancies using 2-[18F]-fluoro-2-deoxy-d-glucose (18F-FDG PET CT) with high accuracy and they contribute to decisions regarding diagnosis, staging, recurrence, and treatment response. Here, we report a case of false positive metastatic mediastinal lymph nodes that were diagnosed by 18F-FDG PET CT in a 40-year-old breast cancer patient who had undergone preoperative evaluation. Right paratracheal, prevascular, aorticopulmonary, precarinal, subcarinal, hilar, and subhilar multiple conglomerated mediastinal lymph nodes were revealed in addition to left breast mass and axillary lymph nodes. Mediastinoscopy was performed with biopsy and pathology was reported as granulomatous lymphadenitis. In conclusion, any abnormal FDG accumulation in unusual lymph nodes must be evaluated carefully and confirmed histopathologically.

[Modern diagnostics in breast cancer: nuclear medicine techniques]

The authors discuss the role of nuclear medicine techniques in the modern diagnostics of breast cancer, including the methods currently used in Hungary and the future possibilities.

Diffuse optical imaging and spectroscopy of the breast: a brief outline of history and perspectives

Breast cancer is the most common cancer among women in industrialized countries. At present, X-ray mammography is the gold standard for breast imaging, but has limitations, especially when dense breasts are imaged, as typically occurs in young women. Optical imaging can non-invasively provide information on tissue composition, structure and physiology that can be beneficially exploited for breast lesion detection and identification. In the last few decades optical breast imaging has been investigated, using different geometries (projection imaging and tomography) and measurement techniques (continuous wave, frequency resolved and time resolved approaches). Also, data analysis and display varies significantly, ranging from intensity images to maps of the optical properties (absorption and scattering), tissue composition, and physiological parameters (typically blood volume and oxygenation). This paper outlines the historical evolution of optical imaging and spectroscopy of the breast, highlighting potentialities and limitations, and presents an overview of the main applications and perspectives of the field.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Performance characterization of a new high resolution PET scintillation detector

Performance of a new high resolution PET detection concept is presented. In this new concept, annihilation radiation enters the scintillator detectors edge-on. Each detector module comprises two 8 × 8 LYSO scintillator arrays of 0.91 × 0.91 × 1 mm(3) crystals coupled to two position-sensitive avalanche photodiodes (PSAPDs) mounted on a flex circuit. Appropriate crystal segmentation allows the recording of all three spatial coordinates of the interaction(s) simultaneously with submillimeter resolution. We report an average energy resolution of 14.6 ± 1.7% for 511 keV photons at FWHM. Coincident time resolution was determined to be 2.98 ± 0.13 ns FWHM on average. The coincidence point spread function (PSF) has an average FWHM of 0.837 ± 0.049 mm (using a 500 μm spherical source) and is uniform across the arrays. Both PSF and coincident time resolution degrade when Compton interactions are included in the data. Different blurring factors were evaluated theoretically, resulting in a calculated PSF of 0.793 mm, in good agreement with the measured value.

18F-FDG uptake in lung, breast, and colon cancers: molecular biology correlates and disease characterization

It is hoped that in the not too distant future, noninvasive imaging-based molecular interrogation and characterization of tumors can improve our fundamental understanding of the dynamic biologic behavior of cancer. For example, the new dimension of diagnostic information that is provided by (18)F-FDG PET has led to improved clinical decision making and management changes in a substantial number of patients with cancer. In this context, the aim of this review is to bring together and summarize the current data on the correlation between the underlying molecular biology and the clinical observations of tumor (18)F-FDG accumulation in 3 major human cancers: lung, breast, and colon.

18F-FDG small-animal PET/CT differentiates trastuzumab-responsive from unresponsive human breast cancer xenografts in athymic mice

Breast cancers (BCs) with high human epidermal growth factor receptor type 2 (HER2) expression are most likely to respond to trastuzumab; however, the mechanisms of action of trastuzumab are complex and there are no established biomarkers to accurately monitor treatment outcome in individual patients. Therefore, our aim was to determine, in human BC xenografts in athymic mice treated with trastuzumab, whether there were any changes in (18)F-FDG uptake that were associated with response to the drug and that could have utility in monitoring response in patients.

METHODS

Baseline tumor uptake of (18)F-FDG was measured in mice with MDA-MB-361 HER2-overexpressing xenografts and MDA-MB-231 xenografts with low HER2 expression by small-animal PET imaging on day 0. Mice were treated with phosphate-buffered saline (PBS) or trastuzumab (4 mg/kg), and small-animal PET was repeated 2 d after treatment. Maintenance doses of trastuzumab (2 mg/kg) or PBS were administered on days 7 and 14, and mice were imaged again on days 9 and 16. Tumor uptake was measured as percentage injected dose per gram (%ID/g) by volume-of-interest analysis on days 0 (baseline), 2, 9, and 16, followed by biodistribution studies on day 16. Tumor growth was measured, and a tumor growth index was calculated.

RESULTS

The treatment of mice with trastuzumab, compared with control mice treated with PBS, resulted in a significant decrease in tumor uptake of (18)F-FDG in HER2-overexpressing MDA-MB-361 xenografts after 16 d of treatment (2.6 +/- 0.8 %ID/g vs. 4.6 +/- 1.8 %ID/g, respectively; P < 0.03) but not after 2 or 9 d of treatment (P = 0.28-0.32). In contrast, there was no significant change in the tumor uptake of MDA-MB-231 xenografts with low HER2 expression during the entire course of therapy (4.4 +/- 1.7 %ID/g vs. 3.6 +/- 1.1 %ID/g, respectively; P = 0.31). Trastuzumab treatment, compared with PBS treatment of controls, resulted in significant growth inhibition of MDA-MB-361 xenografts as early as 10 d from the initiation of treatment (tumor growth index, 0.7 +/- 0.2 vs. 1.7 +/- 0.3, respectively; P < 0.0005), whereas no tumor growth inhibition was observed for MDA-MB-231 xenografts (5.3 +/- 2.7 and 5.2 +/- 3.0; P = 0.95).

CONCLUSION

Changes in the tumor uptake of (18)F-FDG after therapy accurately identified responding and nonresponding human BC xenografts in athymic mice treated with trastuzumab; however, diminished glucose utilization did not precede changes in tumor volume.

FDG-PET Dynamic Contrast-Enhanced CT in the Management of Breast Cancer

Breast cancer is a complex disease and molecular imaging may contribute to better management through providing new insight for early detection. Fluorodeoxyglucose (FDG)-PET/CT has made great strides as a functional anatomic technique and recently gained attention in the diagnosis, staging, and follow-up of breast cancer. FDG-PET and CT complement each other's strengths in integrated FDGPET/CT. One-stop-shop whole-body FDG-PET/CT coupled with integrated FDG-PET/CT mammography has also been advocated.

Preoperative Staging of Large Primary Breast Cancer With [18F]Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Compared With Conventional Imaging Procedures

Purpose

To evaluate the utility of positron emission tomography (PET) and [18F]fluorodeoxyglucose in the initial staging of large primary breast tumors.

Patients and Methods

This prospective study was approved by the ethics committee, and all patients gave their informed consent before enrollment. Sixty consecutive patients with large (> 3 cm) primary breast cancer diagnosed by clinical examination and breast magnetic resonance imaging (MRI) were entered onto the study. The mean age was 57 ± 13 years. Chest computed tomography (CT), liver ultrasonography, bone scan, and PET/CT were performed in all patients. All findings were histologically confirmed, and/or at least 1 year of follow-up was required. Correlation between parameters was calculated using Pearson's correlation coefficient. P < .05 was considered statistically significant.

Results

Primary tumor was identified by both PET/CT and MRI in all patients. Multifocal and/or multicentric tumors were found in 19 patients by MRI. Axillary lymph node metastases were found in 20 of 52 patients. Extra-axillary metastatic lymph nodes were also found in three patients. One patient showed an infiltrated lymph node in the contralateral axilla. The sensitivity and specificity for PET/CT to detect axillary lymph nodes metastases were 70% and 100%, respectively. PET/CT diagnosed all extra-axillary lymph nodes. The overall sensitivity and specificity of PET/CT in detecting distant metastases were 100% and 98%, respectively; whereas the sensitivity and specificity of conventional imaging were 60% and 83%, respectively. PET led to a change in the initial staging in 42% of patients.

Conclusion

PET/CT underestimates locoregional lymph node staging in large primary breast cancer patients. PET/CT is a valuable tool to discard unsuspected extra-axillary lymph nodes and distant metastases.

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.

Breast Cancer Treatment in the Era of Molecular Imaging

Molecular imaging employs molecularly targeted probes to visualize and often quantify distinct disease-specific markers and pathways. Modalities like intravital confocal or multiphoton microscopy, near-infrared fluorescence combined with endoscopy, surface reflectance imaging, or fluorescence-mediated tomography, and radionuclide imaging with positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are increasingly used for small animal high-throughput screening, drug development and testing, and monitoring gene therapy experiments. In the clinical treatment of breast cancer, PET and SPECT as well as magnetic resonance-based molecular imaging are already established for the staging of distant disease and intrathoracic nodal status, for patient selection regarding receptor-directed treatments, and to gain early information about treatment efficacy. In the near future, reporter gene imaging during gene therapy and further spatial and qualitative characterization of the disease can become clinically possible with radionuclide and optical methods. Ultimately, it may be expected that every level of breast cancer treatment will be affected by molecular imaging, including screening.

Hypoxic regulation of glucose transport, anaerobic metabolism and angiogenesis in cancer: novel pathways and targets for anticancer therapeutics

Cancer cells require a steady source of metabolic energy in order to continue their uncontrolled growth and proliferation. Accelerated glycolysis is one of the biochemical characteristics of cancer cells. Recent work indicates that glucose transport and metabolism are essential for the posttreatment survival of tumor cells, leading to poor prognosis. Glycolytic breakdown of glucose is preceded by the transport of glucose across the cell membrane, a rate-limiting process mediated by facilitative glucose transporter proteins belonging to the facilitative glucose transporter/solute carrier GLUT/SLC2A family. Tumors frequently show overexpression of GLUTs, especially the hypoxia-responsive GLUT1 and GLUT3 proteins. There are also studies that have reported associations between GLUT expression and proliferative indices, whilst others suggest that GLUT expression may be of prognostic significance. In this article we revisit Warburg's original hypothesis and review the recent clinical and basic research on the expression of GLUT family members in human cancers and in cell lines derived from human tumors. We also explore the links between hypoxia-induced genes, glucose transporters and angiogenic factors. Hypoxic tumors are significantly more malignant, metastatic, radio- and chemoresistant and have a poor prognosis. With the discovery the oxygen-sensitive transcription factor hypoxia-inducible factor (HIF-1) has come a new understanding of the molecular link between hypoxia and deregulated glucose metabolism. HIF-1 induces a number of genes integral to angiogenesis, e.g. vascular endothelial growth factor (VEGF), a process intimately involved with metastatic spread. This knowledge may enhance existing chemotherapeutic strategies so that treatment can be more rationally applied and personalized for cancer patients.

Multicellular tumour spheroid as a model for evaluation of [18F]FDG as biomarker for breast cancer treatment monitoring

Background

In order to explore a pre-clinical method to evaluate if [¹⁸F]FDG is valid for monitoring early response, we investigated the uptake of FDG in Multicellular tumour spheroids (MTS) without and with treatment with five routinely used chemotherapy agents in breast cancer.

Methods

The response to each anticancer treatment was evaluated by measurement of the [¹⁸F]FDG uptake and viable volume of the MTSs after 2 and 3 days of treatment.

Results

The effect of Paclitaxel and Docetaxel on [¹⁸F]FDG uptake per viable volume was more evident in BT474 (up to 55% decrease) than in MCF-7 (up to 25% decrease).

Doxorubicin reduced the [¹⁸F]FDG uptake per viable volume more noticeable in MCF-7 (25%) than in BT474 MTSs.

Tamoxifen reduced the [¹⁸F]FDG uptake per viable volume only in MCF-7 at the highest dose of 1 μM.

No effect of Imatinib was observed.

Conclusion

MTS was shown to be appropriate to investigate the potential of FDG-PET for early breast cancer treatment monitoring; the treatment effect can be observed before any tumour size changes occur.

The combination of PET radiotracers and image analysis in MTS provides a good model to evaluate the relationship between tumour volume and the uptake of metabolic tracer before and after chemotherapy. This feature could be used for screening and selecting PET-tracers for early assessment of treatment response.

In addition, this new method gives a possibility to assess quickly, and in vitro, a good preclinical profile of existing and newly developed anti-cancer drugs.