Role of 2-[18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) in the early assessment of response to chemotherapy in metastatic breast cancer patients

Quarter-Century Transformation of Oncology: Positron Emission Tomography for Patients with Breast Cancer

PET radiotracers have become indispensable in the care of patients with breast cancer. 18F-fluorodeoxyglucose has become the preferred method of many oncologists for systemic staging of breast cancer at initial diagnosis, detecting recurrent disease, and for measuring treatment response after therapy. 18F-Sodium Fluoride is valuable for detection of osseous metastases. 18F-fluoroestradiol is now FDA-approved with multiple appropriate clinical uses. There are multiple PET radiotracers in clinical trials, which may add utility of PET imaging for patients with breast cancer in the future. This article will describe the advances during the last quarter century in PET for patients with breast cancer.

Women's Health Update: Growing Role of PET for Patients with Breast Cancer

Positron Emission Tomography (PET) has been growing in usage for patients with breast cancer, due to an increased number of FDA-approved PET radiotracers pertinent to patients with breast cancer as well as increased prospective evidence for the value of these agents. The leading PET radiotracer for patients with breast cancer is 18F-fluorodeoxyglucose (18F-FDG), which measures glucose metabolism. There is prospective evidence for the use of 18F-FDG PET in systemic staging of newly diagnosed locally advanced breast cancer (stages IIB-IIIC), monitoring breast cancer treatment response, and detecting breast cancer recurrence, particularly in no special type (NST) breast cancer. 16α-18F-fluoro-17β-Fluoroestradiol (18F-FES) is a radiolabeled estrogen which evaluates estrogen receptor (ER) accessible for estrogen binding. There is prospective evidence supporting 18F-FES PET as a predictive biomarker for selecting patients with metastatic breast cancer for endocrine therapies. 18F-FES PET has also been shown to be valuable in the evaluation of ER status of lesions which are difficult to biopsy, for evaluation of ER status in lesions that are equivocal on other imaging modalities, and for selecting optimal dosage of novel ER-targeted systemic therapies in early clinical trials. Multiple investigators have suggested 18F-FES PET will have an increasing role for patients with invasive lobular breast cancer (ILC), which is less optimally evaluated by 18F-FDG PET. Sodium 18F-Fluoride (18F-NaF) evaluates bone turnover and has been effective in evaluation of malignancies which commonly metastasize to bone. In patients with metastatic breast cancer, 18F-NaF PET/CT has demonstrated superior sensitivity for osseous metastases than 99mTc-MDP or CT. In addition to these three FDA-approved PET radiotracers, there are multiple novel radiotracers currently in clinical trials with potential to further increase PET usage for patients with breast cancer.

The Role of PET/CT in Breast Cancer

Female breast cancer has surpassed lung cancer as the most commonly diagnosed cancer worldwide, with an estimated 2.3 million new cases (11.7%), followed by lung cancer (11.4%) The current literature and the National Comprehensive Cancer Network (NCCN) guidelines state that ¹⁸F-FDG PET/CT is not routine for early diagnosis of breast cancer, and rather PET/CT scanning should be performed for patients with stage III disease or when conventional staging studies yield non-diagnostic or suspicious results because this modality has been shown to upstage patients compared to conventional imaging and thus has an impact on disease management and prognosis. Furthermore, with the growing interest in precision therapy in breast cancer, numerous novel radiopharmaceuticals have been developed that target tumor biology and have the potential to non-invasively guide the most appropriate targeted therapy. This review discusses the role of ¹⁸F-FDG PET and other PET tracers beyond FDG in breast cancer imaging.

Novel applications of molecular imaging to guide breast cancer therapy

The goals of precision oncology are to provide targeted drug therapy based on each individual’s specific tumor biology, and to enable the prediction and early assessment of treatment response to allow treatment modification when necessary. Thus, precision oncology aims to maximize treatment success while minimizing the side effects of inadequate or suboptimal therapies. Molecular imaging, through noninvasive assessment of clinically relevant tumor biomarkers across the entire disease burden, has the potential to revolutionize clinical oncology, including breast oncology. In this article, we review breast cancer positron emission tomography (PET) imaging biomarkers for providing early response assessment and predicting treatment outcomes. For 2-¹⁸fluoro-2-deoxy-D-glucose (FDG), a marker of cellular glucose metabolism that is well established for staging multiple types of malignancies including breast cancer, we highlight novel applications for early response assessment. We then review current and future applications of novel PET biomarkers for imaging the steroid receptors, including the estrogen and progesterone receptors, the HER2 receptor, cellular proliferation, and amino acid metabolism.

PET Imaging for Breast Cancer

Imaging plays an integral role in the clinical care of patients with breast cancer. This review article focuses on the use of PET imaging for breast cancer, highlighting the clinical indications and limitations of 2-deoxy-2-[¹⁸F]fluoro-d-glucose (FDG) PET/CT, the potential use of PET/MRI, and 16α-[¹⁸F]fluoroestradiol (FES), a newly approved radiopharmaceutical for estrogen receptor imaging.

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.

Attenuated Salmonella typhimurium-mediated tumour targeting imaging based on peptides

Attenuated bacteria-mediated tumor targeting diagnosis will provide a novel strategy for further cancer treatments owing to the intrinsic facultative anaerobic characteristic of bacteria and rapid proliferation in the tumor sites. In this work, we firstly investigate the in vivo behaviour of the attenuated Salmonella typhimurium (S. typhimuriumΔppGpp/lux) after intravenous injection. S. typhimurium exhibits rapid proliferation in tumor sites after three days of injection through bioluminescence imaging, the Luria-Bertani plate and the Gram-staining assay. In contrast, S. typhimurium does not proliferate in the normal tissues and could be excreted from the body of mice. Afterwards, a targeting peptide ubiquicidin (UBI) labeled with fluorescent dye Cy5.5 or radionuclide ¹²⁵I was intravenously injected into the mice with or without S. typhimurium treatments for in vivo fluorescence imaging and single-photon emission computed tomography (SPECT/CT) imaging, respectively. The results show that the peptide UBI could specifically target the two independent bacteria-infected tumor models, the 4T1 murine breast cancer model and the CT26 mouse colon cancer model, realizing the sensitive multimodal imaging of tumors. Such a strategy (bacteria-mediated tumor targeting) may further improve the sensitivity to early diagnosis of tumors. We hope that our developed strategy could further be extended to cancer theranostics in the future, bringing good news for cancer patients.

hENT1 reverses chemoresistance by regulating glycolysis in pancreatic cancer

Gemcitabine (GEM) chemotherapy, as the first-line regimen for pancreatic cancer, tends to induce drug resistance, which ultimately worsens the prognosis of patients with pancreatic cancer. Our previous study indicated a close correlation between pancreatic cancer progression and glucose metabolism, especially at the chemoresistant stage, highlighting the importance of the application of 18F-FDG PET dual-phase imaging in the early detection of pancreatic cancer. We speculate that glycolysis, participates in the development of chemoresistance in pancreatic cancer. In this article, we wanted to determine whether manipulating hENT1 expression in pancreatic cancer cells can reverse GEM chemoresistance and whether glucose transport and glycolysis are involved during this process. We found that hENT1 reversed GEM-induced drug resistance by inhibiting glycolysis and altering glucose transport mediated by HIF-1α in pancreatic cancer. Our findings also suggest that 18F-FDG PET dual-phase imaging after the 4th chemotherapy treatment can accurately identify drug-resistant pancreatic tumors and improve hENT1 reversal therapy. Our findings highlight that the dynamic observation of (retention index) RI changes from the beginning of treatment can also be helpful for evaluating the therapeutic effect.

18F-FDG PET/CT for the early prediction of the response rate and survival of patients with recurrent or metastatic breast cancer

The present study aimed to explore the value of fludeoxyglucose F 18 positron emission tomography-computed tomography (PET/CT) for the early prediction of chemotherapy remission rates and survival in patients with recurrent and metastatic breast cancer. A total of 24 patients diagnosed with recurrent or metastatic breast cancer between 2009 and 2014 were enrolled. All patients underwent a PET/CT examination prior to (PET/CT1) and following (PET/CT2) chemotherapy. Differences of PET/CT1 maximal standardized uptake values (SUV_max), PET/CT2 SUV_max, ΔSUV_max and the ΔSUV_max% between objective remission (OR) and non-OR groups were measured. Survival differences between OR and non-OR groups and the overall survival (OS) between metabolic responsive and metabolic non-responsive groups were analyzed. In the present study, it was revealed that ΔSUV_max and ΔSUV_max% were significantly higher in the OR group compared with the non-OR group (P<0.001). Overall survival was significantly prolonged in the OR and metabolic responder groups compared with their respective control groups (P<0.001 and P<0.01, respectively). ΔSUV_max% were significantly positively associated with OS (r²=0.266; P<0.01). In conclusion, PET/CT may be valuable for the early prediction of the chemotherapy efficacy and survival of patients with recurrent or metastatic breast cancer.

Role of Fludeoxyglucose in Breast Cancer: Treatment Response

After an overview of the principles of fludeoxyglucose-PET/computed tomography (CT) in breast cancer, its advantages and limits to evaluate treatment response are discussed. The metabolic information is helpful for early assessment of the response to neoadjuvant chemotherapy and could be used to monitor treatment, especially in aggressive breast cancer subtypes. PET/CT is also a powerful method for early assessment of the treatment response in the metastatic setting. It allows evaluation of different sites of metastases in a single examination and detection of a heterogeneous response. However, to use PET/CT to assess responses, methodology for image acquisition and analysis needs standardization.

Changes in Glucose Metabolism and Blood Flow Following Chemotherapy for Breast Cancer

This article focuses on this application of positron emission tomography (PET) to breast cancer. The article first reviews the PET methodology used for breast cancer response assessment, with an emphasis on quantitative methods. This is followed by a review of results to date for neoadjuvant chemotherapy and therapy of metastatic breast cancer. Preliminary studies with tracers other than (18)F-fluordeoxyglucose are then reviewed. The article ends with a summary and a discussion of future directions.

Positron Emission Tomography in Breast Cancer

Gradually, FDG-PET/CT has been strengthening within the diagnostic algorithms of oncological diseases. In many of these, PET/CT has shown to be useful at different stages of the disease: diagnosis, staging or re-staging, treatment response assessment, and recurrence. Some of the advantages of this imaging modality versus CT, MRI, bone scan, mammography, or ultrasound, are based on its great diagnostic capacity since, according to the radiopharmaceutical used, it reflects metabolic changes that often occur before morphological changes and therefore allows us to stage at diagnosis. Moreover, another advantage of this technique is that it allows us to evaluate the whole body so it can be very useful for the detection of distant disease. With regard to breast cancer, FDG-PET/CT has proven to be important when recurrence is suspected or in the evaluation of treatment response. The technological advancement of PET equipment through the development of new detectors and equipment designed specifically for breast imaging, and the development of more specific radiopharmaceuticals for the study of the different biological processes of breast cancer, will allow progress not only in making the diagnosis of the disease at an early stage but also in enabling personalized therapy for patients with breast cancer.

A phase 2 study of 16α-[18F]-fluoro-17β-estradiol positron emission tomography (FES-PET) as a marker of hormone sensitivity in metastatic breast cancer (MBC)

PURPOSE

16α-[(18)F]-fluoro-17β-estradiol positron emission tomography (FES-PET) quantifies estrogen receptor (ER) expression in tumors and may provide diagnostic benefit.

PROCEDURES

Women with newly diagnosed metastatic breast cancer (MBC) from an ER-positive primary tumor were imaged before starting endocrine therapy. FES uptake was evaluated qualitatively and quantitatively, and associated with response and with ER expression.

RESULTS

Nineteen patients underwent FES imaging. Fifteen had a biopsy of a metastasis and 15 were evaluable for response. Five patients had quantitatively low FES uptake, six had at least one site of qualitatively FES-negative disease. All patients with an ER-negative biopsy had both low uptake and at least one site of FES-negative disease. Of response-evaluable patients, 2/2 with low FES standard uptake value tumors had progressive disease within 6 months, as did 2/3 with qualitatively FES-negative tumors.

CONCLUSIONS

Low/absent FES uptake correlates with lack of ER expression. FES-positron emission tomography can help identify patients with endocrine resistant disease and safely measures ER in MBC.

Recent Trends in PET Image Interpretations Using Volumetric and Texture-based Quantification Methods in Nuclear Oncology

Image quantification studies in positron emission tomography/computed tomography (PET/CT) are of immense importance in the diagnosis and follow-up of variety of cancers. In this review we have described the current image quantification methodologies employed in (18)F-fluorodeoxyglucose ((18)F-FDG) PET in major oncological conditions with particular emphasis on tumor heterogeneity studies. We have described various quantitative parameters being used in PET image analysis. The main contemporary methodology is to measure tumor metabolic activity; however, analysis of other image-related parameters is also increasing. Primarily, we have identified the existing role of tumor heterogeneity studies in major cancers using (18)F-FDG PET. We have also described some newer radiopharmaceuticals other than (18)F-FDG being studied/used in the management of these cancers. Tumor heterogeneity studies are being performed in almost all major oncological conditions using (18)F-FDG PET. The role of these studies is very promising in the management of these conditions.

Positron emission tomography: clinical applications in oncology. Part 1

Positron emission tomography is a functional diagnostic imaging technique, which can accurately measure in vivo distribution of a radiopharmaceutical with high resolution. The ability of positron emission tomography to study various biologic processes opens up new possibilities for both research and day-to-day clinical use. Positron emission tomography has progressed rapidly from being a research technique in laboratories to a routine clinical imaging modality becoming part of armamentarium for the medical profession. The most widely used radiotracer in positron emission tomography is 18F-fluoro-2-deoxy-D-glucose (FDG), which is an analog of glucose. FDG uptake in cells is directly proportional to glucose metabolism of cells. Since glucose metabolism is increased many fold in malignant tumors, positron emission tomography has a high sensitivity and high negative predictive value. Positron emission tomography with FDG is now the standard of care in initial staging, monitoring the response to therapy and management of lung cancer, colorectal cancer, lymphoma, melanoma, esophageal cancer, head and neck cancer and breast cancer. The aim of this article is to review the clinical applications of positron emission tomography in oncology.

Molecular imaging for monitoring treatment response in breast cancer patients

Currently, tumour response following drug treatment is based on measurement of anatomical size changes. This is often done according to Response Evaluation Criteria in Solid Tumours (RECIST) and is generally performed every 2-3 cycles. Bone metastases, being the most common site of distant metastases in breast cancer, are not measurable by RECIST. The standard response measurement provides no insight in changes of molecular characteristics. In the era of targeted medicine, knowledge of specific molecular tumour characteristics becomes more important. A potential way to assess this is by means of molecular imaging. Molecular imaging can visualise general tumour processes, such as glucose metabolism with (18)F-fluorodeoxyglucose ((18)F-FDG) and DNA synthesis with (18)F-fluorodeoxythymidine ((18)F-FLT). In addition, an increasing number of more specific targets, such as hormone receptors, growth factor receptors, and growth factors can be visualised. In the future molecular imaging may thus be of value for personalised treatment-selection by providing insight in the expression of these drug targets. Additionally, when molecular changes can be detected early during therapy, this may serve as early predictor of response. However, in order to define clinical utility of this approach results from (ongoing) clinical trials is required. In this review we summarise the potential role of molecular imaging of general tumour processes as well as hormone receptors, growth factor receptors, and tumour micro-environment for predicting and monitoring treatment response in breast cancer patients.

Imaging in oncology--over a century of advances

Over the past 120 years, the discipline of oncology has evolved so that a multitude of anatomical and increasingly complex functional imaging techniques are now applicable in both clinical and research platforms. This Timeline article revisits the achievements of the pioneer techniques in cancer imaging, discusses how these techniques have changed over time, provides some examples of clinical importance, and ventures to explain how imaging will remodel the future of modern oncology.

Circulating tumor cells in breast cancer: a tool whose time has come of age

Circulating tumor cells (CTCs) are isolated tumor cells disseminated from the site of disease in metastatic and/or primary cancers, including breast cancer, that can be identified and measured in the peripheral blood of patients. As recent technical advances have rendered it easier to reproducibly and repeatedly sample this population of cells with a high degree of accuracy, these cells represent an attractive surrogate marker of the site of disease. Currently, CTCs are being integrated into clinical trial design as a surrogate for phenotypic and genotypic markers in correlation with development of molecularly targeted therapies. As CTCs play a crucial role in tumor dissemination, translational research is implicating CTCs in several biological processes, including epithelial to mesenchymal transition. In this mini-review, we review CTCs in metastatic breast cancer, and discuss their clinical utility for assessing prognosis and monitoring response to therapy. We will also introduce their utility in pharmacodynamic monitoring for rational selection of molecularly targeted therapies and briefly address how they can help elucidate the biology of cancer metastasis.

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.

PET and PET-CT Imaging in Treatment Monitoring of Breast Cancer

Breast cancer is one of the more responsive solid tumors with a wide range of systemic therapy options. The treatment of newly diagnosed breast cancer is primarily determined by the extent of disease and generally includes surgery, radiation, and chemotherapy. This article discusses the PET and PET-CT modalities for evaluating treatment response in breast cancer.

Monitoring response to therapeutic interventions in patients with cancer

Positron emission tomography (PET) and PET/computed tomography (CT) with the glucose analog (18)F-fluorodeoxyglucose (FDG) are increasingly used to assess response to therapy in patients, and there is converging evidence that changes in glucose utilization during therapy can be used to predict clinical outcome. Today, integrated PET/CT systems have mainly replaced stand-alone PET devices, providing the opportunity to integrate morphologic information and functional information. However, the use of PET/CT systems also gives rise to methodological challenges for the quantitative analysis of PET scans for treatment monitoring. Recently published single-center studies demonstrate that FDG-PET and FDG-PET/CT have been successfully used for monitoring of tumor response to cytotoxic therapy in a variety of tumor entities. The potential early identification of nonresponding tumors provides an opportunity to alter treatment regimens according to the individual chemosensitivity of the tumor tissue. In this article, we review the methodological background to monitoring of cancer treatment with PET/CT, the diagnostic and prognostic performance of PET/CT for predicting tumor response with the glucose analog FDG in various tumor entities, and the clinical potential of new imaging probes. In addition, the future direction of research and clinical applications is discussed.

Circulating tumor cells and [18F]fluorodeoxyglucose positron emission tomography/computed tomography for outcome prediction in metastatic breast cancer

PURPOSE

Circulating tumor cells (CTCs) and [(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) are two new promising tools for therapeutic monitoring. In this study, we compared the prognostic value of CTC and FDG-PET/CT monitoring during systemic therapy for metastatic breast cancer (MBC).

PATIENTS AND METHODS

A retrospective analyses of 115 MBC patients who started a new line of therapy and who had CTC counts and FDG-PET/CT scans performed at baseline and at 9 to 12 weeks during therapy (midtherapy) was performed. Patients were categorized according to midtherapy CTC counts as favorable (ie, < five CTCs/7.5 mL blood) or unfavorable (> or = five CTCs/7.5 mL blood) outcomes. CTC counts and FDG-PET/CT response at midtherapy were compared, and univariate and multivariate analyses were performed to identify factors associated with survival.

RESULTS

In 102 evaluable patients, the median overall survival time was 14 months (range, 1 to > 41 months). Midtherapy CTC levels correlated with FDG-PET/CT response in 68 (67%) of 102 evaluable patients. In univariate analysis, midtherapy CTC counts and FDG-PET/CT response predicted overall survival (P < .001 and P = .001, respectively). FDG-PET/CT predicted overall survival (P = .0086) in 31 (91%) of 34 discordant patients who had fewer than five CTCs at midtherapy. Only midtherapy CTC levels remained significant in a multivariate analysis (P = .004).

CONCLUSION

Detection of five or more CTCs during therapeutic monitoring can accurately predict prognosis in MBC beyond metabolic response. FDG-PET/CT deserves a role in patients who have fewer than five CTCs at midtherapy. Prospective trials should evaluate the most sensitive and cost-effective modality for therapeutic monitoring in MBC.

Response to therapy in breast cancer

Increasing numbers of patients with newly diagnosed breast cancer receive primary systemic therapy followed by surgery. Histopathology provides an accurate assessment of treatment efficacy on the basis of the extent of residual tumor and regressive changes within tumor tissue. However, only approximately 20% of breast cancer patients achieve a pathologic complete response, a fact that necessitates methods for monitoring therapeutic effectiveness early during therapy. (18)F-FDG PET and (18)F-FDG PET/CT provide essential information regarding a response to primary chemotherapy. Patients with low tumor metabolic activity on pretreatment (18)F-FDG PET are not likely to achieve a histopathologic response. The degree of changes in (18)F-FDG uptake after the initiation of therapy is correlated with the histopathologic response after the completion of therapy. Thus, tumor metabolic changes assessed early during therapy predict therapeutic effectiveness in individual patients. Early identification of ineffective therapy also might be helpful in patients with metastatic breast cancer because many palliative treatment options are available. Changes in metabolic activity generally occur earlier than changes in tumor size, which is the current standard for the assessment of a response. Although treatment stratification based on a metabolic response is an exciting potential application of PET, specific PET response assessment criteria still need to be developed and validated on the basis of patient outcomes before changes in treatment regimens can be implemented. There is increasing clinical evidence for metastatic breast cancer and other tumors that (18)F-FDG PET/CT is the most accurate imaging procedure for assessment of the response at the end of treatment when both CT information and tumor metabolic activity are considered. Importantly, in the setting of primary chemotherapy, neither PET/CT nor conventional imaging procedures can assess the extent of residual breast cancer as accurately as histopathology. Observation of changes in tumor blood flow or tumor cell proliferation is an additional encouraging approach for predicting a response. Ultimately, the prediction of therapeutic effectiveness by PET and PET/CT could help to individualize treatment and to avoid ineffective chemotherapies, with their associated toxicities.

Blood flow and glucose metabolism in stage IV breast cancer: heterogeneity of response during chemotherapy

Objective

The purpose of the study was to compare early changes in blood flow (BF) and glucose metabolism (MR_glu) in metastatic breast cancer lesions of patients treated with chemotherapy.

Methods

Eleven women with stage IV cancer and lesions in breast, lymph nodes, liver, and bone were scanned before treatment and after the first course of chemotherapy. BF, distribution volume of water (V_d), MR_glu/BF ratio, MR_glu and its corresponding rate constants K₁ and k₃ were compared per tumor lesion before and during therapy.

Results

At baseline, mean BF and MR_glu varied among different tumor lesions, but mean V_d was comparable in all lesions. After one course of chemotherapy, mean MR_glu decreased in all lesions. Mean BF decreased in breast and node lesions and increased in bone lesions. V_d decreased in breast and nodes, but did not change in bone lesions. The MR_glu/BF ratio decreased in breast and bone lesions and increased in node lesions. In patients with multiple tumor lesions BF and MR_glu response could be very heterogeneous, even within similar types of metastases. BF and MR_glu increased in lesions of patients who experienced early disease progression or showed no response during clinical follow-up.

Conclusion

BF and MR_glu changes separately give unique information on different aspects of tumor response to chemotherapy. Changes in BF and MR_glu parameters can be remarkably heterogeneous in patients with multiple lesions.

Comparison of diffuse optical tomography of human breast with whole-body and breast-only positron emission tomography

We acquire and compare three-dimensional tomographic breast images of three females with suspicious masses using diffuse optical tomography (DOT) and positron emission tomography (PET). Co-registration of DOT and PET images was facilitated by a mutual information maximization algorithm. We also compared DOT and whole-body PET images of 14 patients with breast abnormalities. Positive correlations were found between total hemoglobin concentration and tissue scattering measured by DOT, and fluorodeoxyglucose (18F-FDG) uptake. In light of these observations, we suggest potential benefits of combining both PET and DOT for characterization of breast lesions.

Bone metastases in patients with metastatic breast cancer: morphologic and metabolic monitoring of response to systemic therapy with integrated PET/CT

PURPOSE

To retrospectively compare morphologic and metabolic changes in bone metastases in response to systemic therapy in patients with metastatic breast cancer (MBC) with integrated positron emission tomography (PET)/computed tomography (CT).

MATERIALS AND METHODS

The institutional review board waived the requirement for informed consent and approved this HIPAA-compliant study. A retrospective analysis was performed with 102 women (mean age, 55 years) with MBC who received systemic treatment. All patients underwent integrated PET/CT before and after treatment. Two reviewers analyzed the images in consensus. Morphologic changes, including morphologic patterns, and lesion attenuation were evaluated. Standardized uptake value (SUV) and total lesion glycolysis (TLG) were analyzed to evaluate metabolic changes. Uni- and multivariate analyses were performed to identify factors that enabled response duration (RD) to be predicted.

RESULTS

At baseline, the morphologic patterns of the target lesions were lytic (n = 33), sclerotic (n = 22), mixed (n = 42), and unclassified (n = 5). Progression of sclerotic change after treatment was identified in 49 patients (48%). After treatment, the mean attenuation of the lesion increased, whereas the mean SUV and TLG decreased. Increases in attenuation correlated significantly with decreases in SUV (r = -0.510, P < .001) and TLG (r = -0.491, P < . 001). Univariate analysis revealed that the increase in attenuation and the decrease in SUV were potential predictors of RD. Multivariate analysis revealed that an increase in the change in SUV was a significant predictor of RD (relative risk, 2.4; P = .003).

CONCLUSION

A decrease in SUV after treatment was an independent predictor of RD in patients with MBC who had bone metastases.

Use of palliative radiotherapy trials for clinical biomarker development

INTRODUCTION

Approximately one quarter of all cancer patients will require palliative radiation treatment at some point during the course of their disease, but only a minority of these patients are entered in clinical trials.

ETHICAL ASSESSMENT OF BIOMARKERS IN PALLIATIVE RADIOTHERAPY TRIALS

We review the literature debating the ethics of inclusion of "palliative" patients on clinical trials. We suggest that these patients provide a potentially valuable resource that can be leveraged to facilitate the discovery and validation of biomarkers predictive of radiation response and toxicity. In addition, this patient population offers valuable opportunities to test combination of radiation and targeted therapies to screen for activity, toxicity and biomarkers in a relatively safe manner.

CONCLUSION

Patients undergoing palliative radiation therapy may provide new opportunities for the development and testing of predictive radiotherapy biomarkers as well as affording opportunities to test combinations of radiation and targeted therapies.

FDG PET, PET/CT, and breast cancer imaging

Currently, the clinical role of positron emission tomography (PET) and PET/computed tomography (CT) in patients with breast cancer is to provide additional information in select scenarios in which results of conventional imaging are indeterminate or of limited utility. There is currently no clinical role for fluorodeoxyglucose (FDG) PET in detection of breast cancer or evaluation of axillary lymph nodes, but these are areas of active research. FDG PET is complementary to conventional staging procedures and should not be a replacement for either bone scintigraphy or diagnostic CT. FDG PET and PET/CT have been shown to be particularly useful in the restaging of breast cancer, in evaluation of response to therapy, and as a problem-solving method when results of conventional imaging are equivocal. In these situations, FDG PET often demonstrates locoregional or unsuspected distant disease that affects management. PET has demonstrated a particular capability for evaluation of chemotherapy response in both patients with locally advanced breast carcinoma and those with metastatic disease.

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.

FDG-PET Evaluation of Response to Treatment

This article discusses evaluating response after and during therapy in various settings and for the types of cancers for which ample evidence demonstrates that PET imaging with flourodeoxyglucose provides a valuable surrogate for response to therapy. It also briefly discusses pitfalls in obtaining an optimal assessment of response and issues that need further attention for this modality to become established as an independent predictor of response to anticancer therapy.

[18F]FDG-PET predicts complete pathological response of breast cancer to neoadjuvant chemotherapy

PURPOSE

To evaluate, in breast cancer patients treated by neoadjuvant chemotherapy, the predictive value of reduction in FDG uptake with regard to complete pathological response (pCR).

METHODS

Forty-seven women with non-metastatic, non-inflammatory, large or locally advanced breast cancer were included. Tumour uptake of FDG was evaluated before and after the first course of neoadjuvant chemotherapy. Four indices were used: maximal and average SUV without or with correction by body surface area and glycaemia (SUV(max), SUV(avg), SUV(max-BSA-G) and SUV(avg-BSA-G), respectively). The predictive value of reduction in FDG uptake with respect to pCR was studied by logistic regression analysis. Relationships between baseline [(18)F]FDG uptake and prognostic parameters were assessed.

RESULTS

The relative decrease in FDG uptake (DeltaSUV) after the first course of neoadjuvant chemotherapy was significantly greater in the pCR group than in the non-pCR group (p < 0.000066). The four FDG uptake indices were all strongly correlated with each other. A decrease in SUV(max-BSA-G) of 85.4% +/- 21.9% was found in pCR patients, versus 22.6% +/- 36.6% in non-pCR patients. DeltaSUV(max-BSA-G) <-60% predicted the pCR with an accuracy of 87% and DeltaSUVs were found to be only factors predictive of the pCR at multivariate analysis. An elevated baseline SUV was associated with high mitotic activity (p < 0.0016), tumour grading (p < 0.004), high nuclear pleomorphism score (p < 0.03) and negative hormonal receptor status (p < 0.005).

CONCLUSION

In breast cancer patients, after only one course of neoadjuvant chemotherapy the reduction in FDG uptake is an early and powerful predictor of pCR.

Promise and Progress for Functional and Molecular Imaging of Response to Targeted Therapies

Biomarkers to predict or monitor therapy response are becoming essential components of drug developer's armamentaria. Molecular and functional imaging has particular promise as a biomarker for anticancer therapies because it is non-invasive, can be used longitudinally and provides information on the whole patient or tumor. Despite this promise, molecular or functional imaging endpoints are not routinely incorporated into clinical trial design. As the costs of clinical trials and drug development become prohibitively more expensive, the need for improved biomarkers has become imperative and thus, the relatively high cost of imaging is justified. Imaging endpoints, such as Diffusion-Weighted MRI, DCE-MRI and FDG-PET have the potential to make drug development more efficient at all phases, from discovery screening with in vivo pharmacodynamics in animal models through the phase III enrichment of the patient population for potential responders. This review focuses on the progress of imaging responses to new classes of anti-cancer therapies targeted against PI3 kinase/AKT, HIF-1alpha and VEGF. The ultimate promise of molecular and functional imaging is to theragnostically predict response prior to commencement of targeted therapy.

Sequential Positron Emission Tomography Using [18F]Fluorodeoxyglucose for Monitoring Response to Chemotherapy in Metastatic Breast Cancer

PURPOSE

To evaluate the clinical value of positron emission tomography (PET) for monitoring chemotherapy in metastatic breast cancer.

EXPERIMENTAL DESIGN

Twenty patients with hormonorefractory or hormonoreceptor-negative multimetastatic breast cancer were prospectively included. PET studies were done at baseline, at day 21 after the first cycle and at day 21 after the third cycle of chemotherapy. Metabolic response was defined based on visual and various modes of standardized uptake value (SUV) analysis of sequential PET studies.

RESULTS

After one cycle, PET indicated a partial response in 12 patients, stable disease in 7 patients, and progressive disease in 1 patient, according to the visual analysis. After three cycles, PET showed a complete response in 5 patients, partial response in 11 patients, stable disease in 3 patients, and progressive disease in 1 patient. Seventy-five percent of the patients showing a metabolic response on visual analysis effectively responded to the treatment. The average SUV decreased on both the second and the third PET study, but only changes measured after three cycles of chemotherapy predicted the clinical response to chemotherapy and the overall survival. All methods for calculating the SUV (normalized for body weight, body surface area, or lean body mass) provided similar results.

CONCLUSION

Semiquantitative analysis of [18F]fluorodeoxyglucose-PET studies done after three cycles of chemotherapy is useful for monitoring the response to chemotherapy in metastatic breast cancer.

Primary Systemic Therapy of Breast Cancer

Primary systemic therapy (PST) or neoadjuvant therapy is used in nonmetastatic breast cancer to treat systemic disease earlier, decrease tumor bulk ideally to a complete pathological response (pCR), and reduce the extent of surgery. The multitude of clinical trials using PST in breast cancer patients has not proven the fundamental hypotheses of improved overall survival and disease-free survival that drove the investigation of PST. The other potential advantages of PST, which include increasing the rate of breast-conserving surgery and predicting outcome to a particular chemotherapy regimen, are also not conclusively established. We examined the published literature on PST for breast cancer and predominantly focused our review on data from large, randomized clinical trials comparing primary systemic chemotherapy with adjuvant chemotherapy, different primary systemic chemotherapy regimens, primary systemic chemotherapy with hormonal therapy, and different preoperative hormonal therapies. Although the optimal neoadjuvant chemotherapy regimen has not been established, a combination of four cycles of an anthracycline followed by four cycles of a taxane appears to produce the highest pCR rate (22%-31%). In patients with HER-2-positive breast cancer, concurrent use of neoadjuvant trastuzumab with an anthracycline-taxane combination has produced provocative results that require further confirmatory studies. Preoperative hormonal therapy is associated with low pCR rates and should be reserved for patients who are poor candidates for systemic chemotherapy. The optimal management of patients with residual disease after the administration of maximum neoadjuvant therapy remains to be defined. The surgical approach, including the role of sentinel node biopsy and delivery of radiation therapy after PST in breast cancer patients, is evolving. Ongoing clinical trials will help identify the subset of patients who would most benefit from the use of PST, establish the most effective PST regimen, and determine the optimal multidisciplinary approach in the management of breast cancer.

Monitoring therapeutic efficacy in breast carcinomas

The aim of imaging during and after neoadjuvant therapy is to document and quantify tumor response: has the tumor size been accurately measured? Certainly, the most exciting information for the oncologists is: can we identify good or nonresponders, and can we predict the pathological response early after the initiation of treatment? This review article will discuss the role and the performance of the different imaging modalities (mammography, ultrasound, magnetic resonance imaging and FDG-PET imaging) for evaluating this therapeutic response. It is important to emphasize that, at this time, clinical examination and conventional imaging (mammography and ultrasound) are the only methods recognized by the international criteria. Magnetic resonance imaging and FDG-PET imaging are very promising for predicting the response early after the initiation of neoadjuvant chemotherapy.

Theoretical study of penalized-likelihood image reconstruction for region of interest quantification

Region of interest (ROI) quantification is an important task in emission tomography (e.g., positron emission tomography and single photon emission computed tomography). It is essential for exploring clinical factors such as tumor activity, growth rate, and the efficacy of therapeutic interventions. Statistical image reconstruction methods based on the penalized maximum-likelihood (PML) or maximum a posteriori principle have been developed for emission tomography to deal with the low signal-to-noise ratio of the emission data. Similar to the filter cut-off frequency in the filtered backprojection method, the regularization parameter in PML reconstruction controls the resolution and noise tradeoff and, hence, affects ROI quantification. In this paper, we theoretically analyze the performance of ROI quantification in PML reconstructions. Building on previous work, we derive simplified theoretical expressions for the bias, variance, and ensemble mean-squared-error (EMSE) of the estimated total activity in an ROI that is surrounded by a uniform background. When the mean and covariance matrix of the activity inside the ROI are known, the theoretical expressions are readily computable and allow for fast evaluation of image quality for ROI quantification with different regularization parameters. The optimum regularization parameter can then be selected to minimize the EMSE. Computer simulations are conducted for small ROIs with variable uniform uptake. The results show that the theoretical predictions match the Monte Carlo results reasonably well.

Current and future use of positron emission tomography (PET) in breast cancer

Positron emission tomography (PET) is a radiotracer imaging method that is increasingly used in both the clinical care of breast cancer patients and in translational breast cancer research. This review emphasizes current and future clinical applications of PET to breast cancer, and highlights some translational research using PET to elucidate the clinical biology of breast cancer. PET principles are reviewed, followed by a review of current applications of (18)F-fluorodeoxyglucose (FDG) to clinical breast cancer care. Finally we review work done with other radiopharmaceuticals beyond FDG designed to image a number of aspects of breast cancer biology, emphasizing those most likely to enter clinical trials in the near future.

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.