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

Synthesis and characterization of 64Cu-labeled Geldanamycin derivative for imaging HSP90 expression in breast cancer

Heat shock protein 90 (HSP90) plays a crucial role in cancer cell growth and metastasis by stabilizing overexpressed signaling proteins. Inhibiting HSP90 has emerged as a promising anti-cancer strategy. In this study, we aimed to develop and characterize a HSP90-targeted molecular imaging probe, [64Cu]Cu-DOTA-BDA-GM, based on a specific HSP90 inhibitor, geldanamycin (GM), for PET imaging of cancers. GM is modified at the C-17 position with 1,4-butane-diamine (BDA) and linked to 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) for 64Cu radiolabeling. We evaluated the probe's specific binding to HSP90-expressing cells using Chinese hamster ovary (CHO) cells and breast cancer cells including MDA-MB-231, MDA-MB-435S, MCF7, and KR-BR-3 cell lines. A competition study with non-radioactive GM-BDA yielded an IC50 value of 1.35 ± 0.14 nM, underscoring the probe's affinity for HSP90. In xenograft models of MDA-MB-231 breast cancer, [64Cu]Cu-DOTA-BDA-GM showcased targeted tumor localization, with significant radioactivity observed up to 18 h post-injection. Blocking studies using unlabeled GM-BDA and treatment with the anticancer drug Vorinostat (SAHA), which can affect the expression and activity of numerous proteins, such as HSPs, confirmed the specificity and sensitivity of the probe in cancer targeting. Additionally, PET/CT imaging in a lung metastasis mouse model revealed increased lung uptake of [64Cu]Cu-DOTA-BDA-GM in metastatic sites, significantly higher than in non-metastatic lungs, illustrating the probe's ability to detect metastatic breast cancer. In conclusion, [64Cu]Cu-DOTA-BDA-GM represents a sensitive and specific approach for identifying HSP90 expression in breast cancer and metastases, offering promising implications for clinical diagnosis and monitoring.

Targeting the Oxytocin Receptor for Breast Cancer Management: A Niche for Peptide Tracers

Breast cancer is a leading cause of death in women, and its management highly depends on early disease diagnosis and monitoring. This remains challenging due to breast cancer's heterogeneity and a scarcity of specific biomarkers that could predict responses to therapy and enable personalized treatment. This Perspective describes the diagnostic landscape for breast cancer management, molecular strategies targeting receptors overexpressed in tumors, the theranostic potential of the oxytocin receptor (OTR) as an emerging breast cancer target, and the development of OTR-specific optical and nuclear tracers to study, visualize, and treat tumors. A special focus is on the chemistry and pharmacology underpinning OTR tracer development, preclinical in vitro and in vivo studies, challenges, and future directions. The use of peptide-based tracers targeting upregulated receptors in cancer is a highly promising strategy complementing current diagnostics and therapies and providing new opportunities to improve cancer management and patient survival.

Obesity and breast cancer

The paper presents an analysis of the latest literature data on the problem of obesity and breast cancer (BC). This review presents modern approaches to the diagnosis of BC in obese patients, new molecular methods of breast imaging,  analyzes the features of the course of BC with obesity depending on menstrual status, molecular biological subtypes of the tumor, the mechanisms of the development of BC against the background of obesity.

Concanavalin A-conjugated gold nanoparticle/silica quantum dot (AuNPs/SiQDs-Con A)-based platform as a fluorescent nanoprobe for the bioimaging of glycan-positive cancer cells

The glycan receptor is a glycosylphosphatidylinositol glycoprotein that is overexpressed on the surface of various cancer cells and has been utilized for wide applications. In the present work, the surface of citrate-capped gold nanoparticles (cit-AuNPs) was modified with mercaptopropionic acid (MPA) molecules to provide carboxylic groups for secondary functionalization with amine anchored-silica quantum dots (Si-NH₂ QDs) to produce cit-AuNPs-MPA/Si-NH₂ QDs fluorescent nanoparticles. Concanavalin A (Con A) molecules were attached through thiol-AuNP bonds to produce the final cit-AuNPs/MPA/Si-NH₂ QDs/Con A smart nanoparticles. The synthesized novel cit-AuNPs/MPA/Si-NH₂ QDs/Con A nanoparticles were utilized for the bioimaging of glycan-overexpressed breast cancer cells. Fluorescence microscopy and flow cytometry results revealed that the cit-AuNPs/MPA/Si-NH₂ QDs/Con A NPs can be efficiently taken up by cancer cells, with differentiating ability between overexpressed cancer cells and low-expressed normal cells. The cellular viability of the cit-AuNPs/MPA/Si-NH₂ QDs/Con A NPs was tested by the MTT test, proving their biocompatible nature at the 200 μg mL^-1 level. In conclusion, the fabricated cit-AuNPs/MPA/Si-NH₂ QDs/Con A NPs could be utilized for the bioimaging of MCF-7 cancer cells even in the clinical setting after proper in vivo validation.

Diabetes, Obesity, and Inflammation: Impact on Clinical and Radiographic Features of Breast Cancer

Obesity, diabetes, and inflammation increase the risk of breast cancer, the most common malignancy in women. One of the mainstays of breast cancer treatment and improving outcomes is early detection through imaging-based screening. There may be a role for individualized imaging strategies for patients with certain co-morbidities. Herein, we review the literature regarding the accuracy of conventional imaging modalities in obese and diabetic women, the potential role of anti-inflammatory agents to improve detection, and the novel molecular imaging techniques that may have a role for breast cancer screening in these patients. We demonstrate that with conventional imaging modalities, increased sensitivity often comes with a loss of specificity, resulting in unnecessary biopsies and overtreatment. Obese women have body size limitations that impair image quality, and diabetes increases the risk for dense breast tis-sue. Increased density is known to obscure the diagnosis of cancer on routine screening mammography. Novel molecu-lar imaging agents with targets such as estrogen receptor, human epidermal growth factor receptor 2 (HER2), pyrimi-dine analogues, and ligand-targeted receptor probes, among others, have potential to reduce false positive results. They can also improve detection rates with increased resolution and inform therapeutic decision making. These emerg-ing imaging techniques promise to improve breast cancer diagnosis in obese patients with diabetes who have dense breasts, but more work is needed to validate their clinical application.

Positron Emission Mammography (PEM) in the diagnosis of breast cancer: A systematic review and economic evaluation

Background: Positron Emission Mammography (PEM) is an imaging technique which is increasing focuses on imaging the chest instead of imaging the whole body. The aim of this study was to conduct a systematic review of the clinical efficacy and coste-ffectiveness of PEM technology, as compared with PET, as a diagnostic method used for breast cancer patients.

Methods: The present study was a Health Technology Assessment (HTA), which was conducted via a systematic review of clinical efficacy and cost-effectiveness of the methods based on domestic evidence. To evaluate the efficacy of the PEM diagnostic method, as compared with PET, we used efficacy indices, including Sensitivity, Specificity, Accuracy, PPV, and NPV. The required data were collected through a meta-analysis of studies published in electronic databases from 1990 to 2016. In addition, direct costs in both methods were estimated and finally, a cost-effectiveness analysis was performed using the results of the study. Also, a one-way sensitivity analysis was performed to examine the effects of parameters’ uncertainty in the model. In this study, we used STATA software to integrate the results of studies with similar parameters.

Results: A total of 722 cases (N) were obtained from the five final studies. The results of the meta-analysis performed on the collected data showed that the two methods were identical in terms of the Specificity and PPV parameters. However, as to Sensitivity, NPV, and Accuracy parameters, the PEM method was superior to the PET for diagnosis of primary breast cancer. The total cost of using PEM and PET was $1737385.7 and $1940903.5, respectively, and the cost of a one-time scan (cost per unit) using PEM and PET devices was $86.82 and $157.63, respectively. As compared with the PET method, the use of the PEM diagnostic method for diagnosis of breast cancer was cost-effective in terms of all the five studied parameters (it was definitely cost-effective for four parameters and was also considered as cost-effective for another index, since ICER was below the threshold).

Conclusion: The results showed that the use of PEM technology for the diagnosis of primary breast cancer is more cost-effective than PET technology; thus, due to the wide range of PET technology in different fields, it is recommended that this method should be used in other areas of priority.

PET Imaging Agents (FES, FFNP, and FDHT) for Estrogen, Androgen, and Progesterone Receptors to Improve Management of Breast and Prostate Cancers by Functional Imaging

Many breast and prostate cancers are driven by the action of steroid hormones on their cognate receptors in primary tumors and in metastases, and endocrine therapies that inhibit hormone production or block the action of these receptors provide clinical benefit to many but not all of these cancer patients. Because it is difficult to predict which individuals will be helped by endocrine therapies and which will not, positron emission tomography (PET) imaging of estrogen receptor (ER) and progesterone receptor (PgR) in breast cancer, and androgen receptor (AR) in prostate cancer can provide useful, often functional, information on the likelihood of endocrine therapy response in individual patients. This review covers our development of three PET imaging agents, 16α-[18F]fluoroestradiol (FES) for ER, 21-[18F]fluoro-furanyl-nor-progesterone (FFNP) for PgR, and 16β-[18F]fluoro-5α-dihydrotestosterone (FDHT) for AR, and the evolution of their clinical use. For these agents, the pathway from concept through development tracks with an emerging understanding of critical performance criteria that is needed for successful PET imaging of these low-abundance receptor targets. Progress in the ongoing evaluation of what they can add to the clinical management of breast and prostate cancers reflects our increased understanding of these diseases and of optimal strategies for predicting the success of clinical endocrine therapies.

Spectrofluorimetric cytosensing of colorectal cancer cells using terbium-doped dendritic fibrous nano-silica functionalized by folic acid: A novel optical cytosensor for cancer detection

A novel fluorescent probe for detection of HT 29 cancer cells was developed based on terbium-doped dendritic fibrous nanosilica functionalized by folic acid (Tb@KCC-1-NH₂-FA). Using this probe, fluorescence signals was emitted by Tb@KCC-1-NH₂-FA at 490 nm by applying 380 nm as excitation wavelength. The reported probe is based on the interaction between FA decorated on the surface of Tb@KCC-1-NH₂-FA and folate receptor (FR) which is overexpressed on the surface of the most of cancer cells. Fluorescence microscopy and flow cytometry were utilized to verify the uptake of Tb@KCC-1-NH₂-FA with FR-positive HT 29 cancer cells. The specificity of Tb@KCC-1-NH₂-FA towards FR-positive cells was approved by staining HEK 293 cells as FR-negative cells with Tb@KCC-1-NH₂-FA which obtained results approved selective differentiation of normal cells with the FA-decorated nanomaterials. The cytotoxicity of Tb@KCC-1-NH₂-FA was evaluated by MTT assay which confirmed their biocompatible nature. Under optimum conditions, this cytosensor is able to detect HT 29 colon cancer from 500 to 6.5 × 10³ cells/mL with lower limit of detection (LLOQ) of 500 cells/mL. Due to the room temperature stability of Tb@KCC-1-NH₂-FA, this cytosensor could be developed in a simple way with exceptional specificity which may show potential applications for early stage detection of colon cancer.

The use of single-photon emission computed tomography-computed tomography in detecting multiple metastatic lymph nodes in patients with breast cancer

AIM

The aim of the present study was to determine the accuracy of single-photon emission computed tomography-computed tomography (SPECT-CT) with technetium-99m-sestamibi (Tc-MIBI) for detecting multiple (>2 nodes) axillary lymph node involvement in patients with breast cancer (BC).

PATIENTS AND METHODS

A total of 184 women with BC were examined. Clinically, axillary lymph nodes were classified as N0 in all cases. Patients underwent SPECT-CT breast and axillary region imaging 10-15 min after a 740 mBq intravenous injection of Tc-MIBI. SPECT-CT data were then verified by definitive histopathological examination (sentinel-node biopsy and/or axillary lymph node dissection were used as reference standard). Diagnostic values of different CT and SPECT signs of multiple (>2) lymph node involvement were evaluated.

RESULTS

Histological examination of excised lymph nodes showed metastatic involvement in 62 (33.7%) out of 184 patients. In fact, 25 (13.6%) patients had more than two lymph node involvements. In another 37 (20.1%) cases the metastasis was revealed in one or two sentinel lymph nodes only. The main SPECT-CT criteria of multiple (>2) lymph node involvement were as follows: the maximum size of the primary tumor (>20 mm), lymph node dimensions (>12 mm along the long axis and >10 mm along the short axis), nodal cortical thickness (>4 mm), round shape, solid structure, quantity of identified abnormal lymph nodes (>1), and intensity of tracer uptake. The developed integrated model offers the possibility to exclude multiple lymph node metastasis (>2) in BC patients with a probability of 99%.

CONCLUSION

This single-center study showed that in patients with BC, a combination of functional and anatomical data that were obtained by using SPECT-CT with Tc-MIBI can significantly improve detectability of multiple (>2) axillary metastases.

Clinical Potential of Human Epidermal Growth Factor Receptor 2 and Human Epidermal Growth Factor Receptor 3 Imaging in Breast Cancer

Increased expression of the human epidermal growth factor receptor (HER) protein family are targets in breast cancer for imaging and therapy. Imaging modalities targeting HER2 and HER3 can diagnose breast cancer with a specific, biologically relevant target. Repeat biopsies do not address heterogeneity intratumorally or between primary disease and metastasis. HER2- and HER3-targeted PET is an important tool to diagnose disease in breast cancer and evaluate response to targeted therapies. PET and single photon emission computed tomography with radiolabeled biomolecules can be used to detect and quantify specific targets, conferring a better understanding of the behavior and effectiveness of treatments.

Imaging Cobalamin Uptake within Malignant Breast Tumors In Vivo

PURPOSE

To image the uptake of cobalamin (Cbl) within malignant breast tumors in vivo.

PROCEDURES

Prior to surgery 20 female patients with clinically suspected breast tumors were intravenously administered 0.25 μg of an In-111 labeled 5-deoxyadenosylcobalamin (AC) analog ([¹¹¹In]AC) and sequentially imaged with whole-body planar (WBP) and single-photon emission computed tomography (SPECT) between 2-5 h and 20-24 h post-injection (P.I.). The tumor to background (T/B) ratio for [¹¹¹In]AC in breast tumors at 2-5 h was correlated to its expression of estrogen (ER), progesterone (PR), and human epidermal growth factor 2 (HER2) receptors. Subsequent pulse chase (PC) experiments in nude mice burdened with the MDA-MB-231 triple-negative (TN) breast tumor xenograft measured the effect that pulses of AC or dexamethasone (DEX) had on [¹¹¹In]AC uptake in both normal murine tissue and the TN breast tumor.

RESULTS

The mean [¹¹¹In]AC T/B ratio of the patients' 18 resected tumors was 5.8. Comparing ER- and PR-positive tumors (n = 11) to TN and HER2-positive tumors (n = 7), the mean [¹¹¹In]AC T/B ratios at 2-5 h P.I. were 3.2 (range 1.8-5.6) and 10.4 (range 3.3-22.5), respectively. Pulses of 2.0 μg of AC at 2, 8, or 24 h; or 40.0 μg of DEX at 24 h prior to injecting 0.5 μg of [¹¹¹In]AC, increased mean tracer uptake in the MDA-MB-231 tumors by 26.4, 71.5, 92.6, and 49.1 %, respectively. Only the 2- and 24-h PC intervals concomitantly suppressed [¹¹¹In]AC uptake in normal murine tissue while enhancing [¹¹¹In]AC uptake in MDA-MB-231 tumors.

CONCLUSION

The uptake of Cbl within malignant breast tumors can be imaged clinically. Cbl uptake is greatest in TN and HER2-positive breast tumors. A solitary bolus of AC or DEX increases the [¹¹¹In]AC uptake within a breast tumor in vivo. Investigating the cytogenetic mechanisms controlling the endocytosis of Cbl in malignant breast tumors is warranted.

Breast cancer diagnosis: Imaging techniques and biochemical markers

Breast cancer is a complex disease which is found as the second cause of cancer-associated death among women. Accumulating of evidence indicated that various factors (i.e., gentical and envirmental factors) could be associated with initiation and progression of breast cancer. Diagnosis of breast cancer patients in early stages is one of important aspects of breast cancer treatment. Among of various diagnosis platforms, imaging techniques are main diagnosis approaches which could provide valuable data on patients with breast cancer. It has been showed that various imaging techniques such as mammography, magnetic resonance imaging (MRI), positron-emission tomography (PET), Computed tomography (CT), and single-photon emission computed tomography (SPECT) could be used for diagnosis and monitoring patients with breast cancer in various stages. Beside, imaging techniques, utilization of biochemical biomarkers such as proteins, DNAs, mRNAs, and microRNAs could be employed as new diagnosis and therapeutic tools for patients with breast cancer. Here, we summarized various imaging techniques and biochemical biomarkers could be utilized as diagnosis of patients with breast cancer. Moreover, we highlighted microRNAs and exosomes as new diagnosis and therapeutic biomarkers for monitoring patients with breast cancer.

Radioiodination and preclinical evaluation of 4-benzyl-1-(3-[125I]-iodobenzylsulfonyl)piperidine as a breast tumor imaging tracer in mouse

OBJECTIVE

4-Benzyl-1-(3-iodobenzylsulfonyl)piperidine, 4-B-IBSP, has shown high-binding affinity to both sigma (σ) receptors in our previous work. In current study, radiolabeling and preclinical evaluation of 4-benzyl-1-(3-[¹²⁵I]-iodobenzylsulfonyl)piperidine, 4-B-[¹²⁵I]IBSP, in human ductal breast carcinoma (T47D) cells and in breast adenocarcinoma-bearing BALB/c mice are described.

METHODS

Radioiodination of this new σ ligand was performed by a palladium-catalyzed stannylation approach followed by oxidative iododestannylation reaction using Iodo-Gen. Competition-binding assays for binding of 4-B-[¹²⁵I]IBSP to guinea pig brain membranes and to T47D cells were performed with known σ ligands. The selectivity and binding characteristics (B _max and K _d) were analyzed. In vitro stability and in vivo blood metabolism studies were also evaluated. Moreover, biodistribution studies were performed in normal and into the tumor-bearing mice at interval time points post-injection (p.i.). Both in vitro and in vivo blockade experiments were done in the presence of the σ receptors blocking agents.

RESULTS

Radioiodinated ligand was obtained in high yield and high specific activity. The σ inhibition constants (K _i, nM) for 4-(3-iodobenzyl)-1-(benzylsulfonyl)piperazine (4-IBBSPz), (+)-pentazocine, haloperidol, DTG, and 4-B-IBSP were 1.37 ± 0.19, 3.90 ± 0.77, 2.69 ± 0.33, 30.62 ± 2.01, and 0.61 ± 0.05, respectively. 4-B-[¹²⁵I]IBSP bound to σ receptor sites preferably to very high-affinity binding sites on T47D cells. The radioligand showed acceptable in vitro and in vivo stabilities in the blood pool. However, in vivo biodistribution studies in normal Swiss albino mice revealed fast clearance of 4-B-[¹²⁵I]IBSP from blood and the other normal organs. Biodistribution experiments of 4-B-[¹²⁵I]IBSP in breast adenocarcinoma tumor-bearing BALB/c mice showed a relatively high tumor uptake at 30 min p.i. (4.13 ± 0.95) that reaches to 1.57 ± 0.24 even after 240 min p.i. A pre-injection of 4-B-IBSP and haloperidol with 4-B-[¹²⁵I]IBSP resulted in 36-57% decrease in activity in the tumor, liver, and brain at 60 min p.i.

CONCLUSIONS

The high affinity of 4-B-[¹²⁵I]IBSP to σ receptor-binding sites, its relatively high uptake, and preferential retention in the tumor as well as an increasing trend observed in the tumor to blood and in the tumor to muscle ratios suggests that an iodine-123 labeled counterpart, 4-B-[¹²³I]IBSP, would be a promising σ radioligand for pursuing further studies to assess its potential for breast tumors imaging with SPECT.

Synthesis and preliminary evaluation of a 18 F-labeled ethisterone derivative [18 F]EAEF for progesterone receptor targeting

To develop a novel progesterone receptor-targeting probe for positron emission tomography imaging, an ethisterone derivative [¹⁸ F]EAEF was designed and prepared in high decay-corrected radiochemical yield (30-35%) with good radiochemical purity (>98%). [¹⁸ F]EAEF is a lipophilic tracer (logP = 0.53 ± 0.06) with very good stability in saline and serum. In the biodistribution study, high radioactivity accumulation of [¹⁸ F]EAEF were found in uterus (5.73 ± 1.83% ID/g) and ovary (4.05 ± 0.73% ID/g) at 2 hr postinjection (p.i.), which have high progesterone receptor expression after treated with estradiol, while the muscle background has very low uptake (0.50 ± 0.17% ID/g). For positron emission tomography imaging, [¹⁸ F]EAEF showed high uptake in progesterone receptor-positive MCF-7 tumor (3.15 ± 0.07% ID/g at 2 hr p.i.) with good tumor to muscle ratio (2.90), and obvious lower tumor uptakes were observed in MCF-7 with EAEF blocking (1.84 ± 0.05% ID/g at 2 hr p.i.) or in progesterone receptor-negative MDA-MB-231 tumor (1.80 ± 0.03% ID/g at 2 hr p.i.). Based on the good stability and specificity of [¹⁸ F]EAEF, it may be a good candidate for imaging progesterone receptor and worth further investigation.

Prorenin receptor acts as a potential molecular target for pancreatic ductal adenocarcinoma diagnosis

Recent studies have implicated the prorenin receptor (PRR) is associated with pancreatic tumorigenesis. We therefore investigated the role of PRR in pancreatic tumorigenesis and assessed whether PRR can serve as a target for imaging diagnosis at early stages of PDAC. Here we show that aberrant expression of PRR in premalignant PanIN lesions, and human PDAC samples, and PDAC cell lines, particularly in Panc-1 cells. Interestingly, PRR expression was positively associated with PDAC progression. Moreover, overexpression of human PRR resulted in increased cell proliferation and decreased apoptosis, while knockdown of human PRR caused decreased cell proliferation and enhanced apoptosis in pancreatic cancer cells. We also observed that overexpression of human PRR enhanced MAPK and PI3K/Akt signaling pathways in PDAC cells, while knockdown of human PRR suppressed both of pathways. The confocal imaging analysis showed that human PRR was highly expressed in Panc-1, ASPC, and Miapaca cells, whereas BXPC-3, and HPAC cells had a significantly lower fluorescent signals. Consistently, the single-photon emission computed tomography (SPET/CT) showed that the uptake of anti-PRR labelled with ¹²⁵I was higher in Panc-1 and ASPC tumors-bearing mice after 96 hours injection. Importantly, tumors in pancreas of Pdx1-cre; LSL-Kras^G12D mice had a significant increased PRR expression and accumulation of radioactivity at 96 h after injection. These data suggest that ¹²⁵I-anti-PRR can detect the orthotopic tumors in Pdx1-cre; LSL-Kras^G12D mice. Therefore, anti-PRR labelled with ¹²⁵I is a promising radiotracer for imaging diagnosis at early stages of pancreatic cancer.

Utilizing the Multiradionuclide Resolving Power of SPECT and Dual Radiolabeled Single Molecules to Assess Treatment Response of Tumors

PURPOSE

Single photon emission computed tomography (SPECT) radionuclide pairs having distinct decay rates and different energy maxima enable simultaneous detection of dual gamma signals and real-time assessment of dynamic functional and molecular processes in vivo. Here, we report image acquisition and quantification protocols for a single molecule labeled with two different radionuclides for functional SPECT imaging.

PROCEDURES

LS370 and LS734 were prepared using modular solid phase peptide synthesis. Each agent has a caspase-3 cleavable reporting motif, flanked by a tyrosine residue and a chelator at the opposite end of molecule. Cell uptake and efflux were assessed in human MDA-MB-231 breast cancer cells. Biodistribution studies were conducted in tumor naive and orthotopic 4T1 metastatic breast cancer tumor mice. NanoSPECT dual-imaging validation and attenuation correction parameters were developed using phantom vials containing varying radionuclide concentrations. Proof-of-principle SPECT imaging was performed in MMTV-PyMT transgenic mice.

RESULTS

LS370 and LS734 were singly or dually radiolabeled with (125)I and (111)In or (99m)Tc. Cell assays demonstrated 11-fold higher percent uptake (P < 0.001) of [(125)I]LS734 (3.6 ± 0.5) compared to [(125)I]LS370 (0.3 ± 0.3) at 2 h. Following chemotherapy, cellular retention of [(125)I]LS734 was 3-fold higher (P < 0.05) than untreated cells. Pharmacokinetics at 1 h postinjection demonstrated longer blood retention (%ID/g) for [(125)I]LS734 (3.2 ± 0.9) compared to [(125)I]LS370 (1.6 ± 0.1). In mice bearing bilateral orthotopic 4T1 tumors, the uptake (%ID/g) was 2.4 ± 0.3 for [(125)I]LS734 and 1.2 ± 0.03 for [(125)I]LS370. The iodinated tyrosine peptide residue label was stable under in vitro conditions for up to 24 h; rapid systemic deiodination (high thyroid uptake) was observed in vivo. Phantom studies using standards demonstrated deconvolution of radionuclide signals based on different gamma ray energies. In MMTV-PyMT mice imaged with dual-labeled [(111)In]-[(125)I]LS734, the gamma signals were separable and quantifiable.

CONCLUSIONS

Image processing protocols were developed for quantitative signal separation resulting from a caspase-3 responsive dual-radiolabeled SPECT probe. Crosstalk unmixing was obtained for multiradionuclide NanoSPECT imaging. In vitro and in vivo data demonstrated structure-activity relationships for developing functional agents for ratiometric SPECT imaging.

Ability of contrast-enhanced ultrasonography to determine clinical responses of breast cancer to neoadjuvant chemotherapy

OBJECTIVE

We aimed to determine whether contrast-enhanced ultrasonography can predict the effects of neoadjuvant chemotherapy on breast cancer.

METHODS

The clinical responses of 63 consecutive patients with breast cancer (T1-4, N0-1, M0) to neoadjuvant chemotherapy between October 2012 and May 2015 were assessed using contrast-enhanced magnetic resonance imaging, positron emission tomography/computed tomography and contrast-enhanced ultrasonography. Perfusion parameters for contrast-enhanced ultrasonography were created from time-intensity curves based on enhancement intensity and temporal changes to objectively evaluate contrast-enhanced ultrasonography findings. The sensitivity, specificity and accuracy of contrast-enhanced ultrasonography, magnetic resonance imaging and positron emission tomography/computed tomography to predict a pathological complete response were compared after confirming the pathological findings of surgical specimens.

RESULTS

Twenty-three (36.5%) of the 63 patients achieved pathological complete response. The sensitivity, specificity and accuracy of contrast-enhanced ultrasonography for predicting pathological complete response were 95.7% (82.5-99.2%), 77.5% (69.9-79.5%) and 84.1% (74.5-86.7%). The sensitivity of contrast-enhanced ultrasonography was significantly greater than that of magnetic resonance imaging (95.7 vs. 69.6%, P = 0.047). The specificity and accuracy were significantly greater and tended to be greater, respectively, for contrast-enhanced ultrasonography than positron emission tomography/computed tomography (specificity, 77.5 vs. 52.5%, P = 0.02; accuracy, 84.1 vs. 69.8%, P = 0.057).

CONCLUSIONS

Contrast-enhanced ultrasonography might serve as a new diagnostic modality when planning therapeutic strategies for patients with breast cancer after neoadjuvant chemotherapy.

A preliminary report of breast cancer screening by positron emission mammography

OBJECTIVE

Fluorine-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET) and PET/computed tomography (PET/CT) have had a considerable impact on the detection of various malignancies. PET and PET/CT are minimally invasive methods that can provide whole-body imaging at one time. Therefore, an FDG-PET cancer screening program has been widely used in Japan. However, the breast cancer detection rate of FDG-PET cancer screening is relatively low. Therefore, FDG-PET screening is not recommended for breast cancer screening. Positron emission mammography (PEM) is a high-resolution molecular breast imaging technology. PEM can detect small breast cancers that cannot be detected on PET or PET/CT images due to limited spatial resolution. We have performed opportunistic breast cancer screening using PEM since 2011. To the best of our knowledge, this is the first report regarding PEM breast cancer screening.

METHODS

This study enrolled 265 women. PEM images were analyzed by agreement of 2 experienced nuclear medicine physicians. The readers were given information from medical interview sheet. US findings were interpreted holistically. The number of participants, patient recall rate, further examination rate, and cancer detection rate by year were calculated.

RESULTS

The overall recall rate was 8.3%; the work-up examination rate was 77.3%, and cancer detection rate was 2.3%. The positive predictive value of PEM was 27.3%. Six cancers were found by PEM screening. Five were invasive cancers and one was ductal carcinoma in situ. Histological tumor sizes were reported in three cases: 0.7, 1.2, and 2 cm.

CONCLUSION

PEM screening appears to have potential for breast cancer screening.

Development of a Radiolabeled Peptide-Based Probe Targeting MT1-MMP for Breast Cancer Detection

Breast cancer is one of the most frequent and aggressive primary tumors among women of all races. Matrix metalloproteinase (MMPs), a family of zinc- and calcium-dependent secreted or membrane anchored endopeptidases, is overexpressed in varieties of diseases including breast cancer. Therefore, noninvasive visualization and quantification of MMP in vivo are of great interest in basic research and clinical application for breast cancer early diagnosis. Herein, we developed a 99mTc labeled membrane type I matrix metalloproteinase (MT1-MMP) specific binding peptide, [99mTc]-(HYNIC-AF7p)(tricine)(TPPTS), for in vivo detection of MDA-MB-231 breast tumor by single photon emission computed tomography (SPECT). [99mTc]-(HYNIC-AF7p)(tricine)(TPPTS) demonstrated nice biostability and high MT1-MMP binding affinity in vitro and in vivo. Tumor-to-muscle ratio was found to reach to the highest (4.17±0.49) at 2 hour after intravenously administration of [99mTc]-(HYNIC-AF7P)(tricine)(TPPTS) into MDA-MB-231 tumor bearing mice. Overall, [99mTc]-(HYNIC-AF7P)(tricine)(TPPTS) demonstrated great potential for MT1-MMP targeted detection in vivo and it would be a promising molecular imaging probe that are probably beneficial to breast cancer early diagnoses.

LAT-1 based primary breast cancer detection by [99m]Tc-labeled DTPA-bis-methionine scintimammography: first results using indigenously developed single vial kit preparation

OBJECTIVE

To evaluate the diagnostic utility of a single vial ready to label with [99m]Tc kit preparation of DTPA-bis-methionine (DTPA-bis-MET) for the detection of primary breast cancer.

METHODS

The conjugate (DTPA-bis-MET) was synthesized by covalently conjugating two molecules of methionine to DTPA and formulated as a single vial ready to label with [99m]Tc lyophilized kit preparations. Thirty female patients (mean age=47.5±11.8 years; range=21-69 years) with radiological/clinical evidence of having primary breast carcinoma were subjected to [99m]Tc-methionine scintigraphy. The whole body (anterior and posterior) imaging was performed on all the patients at 5 minutes, 10 minutes, 1 hour, 2 hours, and 4 hours following an intravenous administration of 555-740 MBq radioactivity of [99m]Tc-methionine. In addition, scintimammography (static images; 256×256 matrix) at 1, 2, and 4 hours was also performed on all the patients.

RESULTS

The resultant radiolabel, that is, [99m]Tc-DTPA-bis-MET, yielded high radiolabeling efficiency (>97.0%), radiochemical purity (166-296 MBq/μmol), and shelf life (>3 months). The radiotracer primarily gets excreted through the kidneys and localizes in the breast cancer lesions with high target-to-nontarget ratios. The mean±SD ratios on the scan-positive lesions acquired at 1, 2, and 4 hours postinjection were 3.6±0.48, 3.10±0.24, and 2.5±0.4, respectively. [99m]Tc-methionine scintimammography demonstrated an excellent sensitivity and positive predictive value of 96.0% each for the detection of primary breast cancer.

CONCLUSION

Ready to label single vial kit formulations of DTPA-bis-MET can be easily synthesized as in-house production and conveniently used for the scintigraphic detection of breast cancer and other methionine-dependent tumors expressing the L-type amino acid transporter-1 receptor. The imaging technique thus could be a potential substitute for the conventional single-photon emission computed tomography (SPECT)-based tumor imaging agents, especially for tracers with nonspecific mitochondrial uptake. However, the diagnostic efficacy of [99m]Tc-methionine needs to be evaluated in a large cohort of patients through further multicentric trials.

Molecular imaging using PET for breast cancer

Molecular imaging can visualize the biological processes at the molecular and cellular levels in vivo using certain tracers for specific molecular targets. Molecular imaging of breast cancer can be performed with various imaging modalities, however, positron emission tomography (PET) is a sensitive and non-invasive molecular imaging technology and this review will focus on PET molecular imaging of breast cancer, such as FDG-PET, FLT-PET, hormone receptor PET, and anti-HER2 PET.

Comparative effectiveness of imaging modalities to determine metastatic breast cancer treatment response

We performed a systematic review to address the comparative effectiveness of different imaging modalities in evaluating treatment response among metastatic breast cancer patients. We searched seven multidisciplinary electronic databases for relevant publications (January 2003-December 2013) and performed dual abstraction of details and results for all clinical studies that involved stage IV breast cancer patients and evaluated imaging for detecting treatment response. Among 159 citations reviewed, 17 single-institution, non-randomized, observational studies met our inclusion criteria. Several studies demonstrate that changes in PET/CT standard uptake values are associated with changes in tumor volume as determined by bone scan, MRI, and/or CT. However, no studies evaluated comparative test performance between modalities or determined relationships between imaging findings and subsequent clinical decisions. Evidence for imaging's effectiveness in determining treatment response among metastatic breast cancer patients is limited. More rigorous research is needed to address imaging's value in this patient population.

Molecular photoacoustic tomography of breast cancer using receptor targeted magnetic iron oxide nanoparticles as contrast agents

In this report, we present a breast imaging technique combining high-resolution near-infrared (NIR) light induced photoacoustic tomography (PAT) with NIR dye-labeled amino-terminal fragments of urokinase plasminogen activator receptor (uPAR) targeted magnetic iron oxide nanoparticles (NIR830-ATF-IONP) for breast cancer imaging using an orthotopic mouse mammary tumor model. We show that accumulation of the targeted nanoparticles in the tumor led to photoacoustic contrast enhancement due to the high absorption of iron oxide nanoparticles (IONP). NIR fluorescence images were used to validate specific delivery of NIR830-ATF-IONP to mouse mammary tumors. We found that systemic delivery of the targeted IONP produced 4- and 10-fold enhancement in photoacoustic signals in the tumor, compared to the tumor of the mice that received non-targeted IONP or control mice. The use of targeted nanoparticles allowed imaging of tumors located as deep as 3.1 cm beneath the normal tissues. Our study indicates the potential of the combination of photoacoustic tomography and receptor-targeted NIR830-ATF-IONP as a clinical tool that can provide improved specificity and sensitivity for breast cancer detection.

Molecular imaging probes for diagnosis and therapy evaluation of breast cancer

Breast cancer is a major cause of cancer death in women where early detection and accurate assessment of therapy response can improve clinical outcomes. Molecular imaging, which includes PET, SPECT, MRI, and optical modalities, provides noninvasive means of detecting biological processes and molecular events in vivo. Molecular imaging has the potential to enhance our understanding of breast cancer biology and effects of drug action during both preclinical and clinical phases of drug development. This has led to the identification of many molecular imaging probes for key processes in breast cancer. Hormone receptors, growth factor receptor, and angiogenic factors, such as ER, PR, HER2, and VEGFR, have been adopted as imaging targets to detect and stage the breast cancer and to monitor the treatment efficacy. Receptor imaging probes are usually composed of targeting moiety attached to a signaling component such as a radionuclide that can be detected using dedicated instruments. Current molecular imaging probes involved in breast cancer diagnosis and therapy evaluation are reviewed, and future of molecular imaging for the preclinical and clinical is explained.

Novel 7α-alkoxy-17α-(4'-halophenylethynyl)estradiols as potential SPECT/PET imaging agents for estrogen receptor expressing tumours: synthesis and binding affinity evaluation

In order to develop potential radiolabelled probes for imaging estrogen receptor (ER) positive tumours, we have synthesized and characterized a series of novel 7α-alkoxy-17α-(4'-iodophenylethynyl)estra-1,3,5(10)-triene-3,17β-diols and 7α-alkoxy-17α-(4'-fluorophenylethynyl)estra-1,3,5(10)-triene-3,17β-diols. The fluoro-substituted compounds showed a higher ER binding affinity than the corresponding iodo-derivatives, where 7α-methoxy- and 17α-(4'-fluorophenylethynyl)estra-1,3,5(10)-triene-3,17β-diol showed the highest ER binding affinities (RBA=80.9% and 78.9%, respectively), among the halophenylethynyl compounds studied and should be further explored as potential PET biomarkers for imaging of ER expressing tumours.

A tomografia computadorizada multislice é ferramenta importante para o estadiamento e seguimento do câncer de mama?

O câncer de mama representa o tipo de câncer mais comum em mulheres e constitui a primeira causa de morte por câncer nesta população. As alterações extramamárias relacionadas ao câncer de mama desempenham papel relevante no prognóstico e tratamento desta entidade, sendo fundamental a realização do diagnóstico correto e das diversas alterações. A maioria dessas manifestações é proveniente do tratamento adotado ou de suas complicações e pode estar associada a comprometimento linfonodal, recorrência locorregional ou metástases a distância.

Advances in molecular imaging for breast cancer detection and characterization

Advances in our ability to assay molecular processes, including gene expression, protein expression, and molecular and cellular biochemistry, have fueled advances in our understanding of breast cancer biology and have led to the identification of new treatments for patients with breast cancer. The ability to measure biologic processes without perturbing them in vivo allows the opportunity to better characterize tumor biology and to assess how biologic and cytotoxic therapies alter critical pathways of tumor response and resistance. By accurately characterizing tumor properties and biologic processes, molecular imaging plays an increasing role in breast cancer science, clinical care in diagnosis and staging, assessment of therapeutic targets, and evaluation of responses to therapies. This review describes the current role and potential of molecular imaging modalities for detection and characterization of breast cancer and focuses primarily on radionuclide-based methods.

Synthesis and biological evaluation of water-soluble progesterone-conjugated probes for magnetic resonance imaging of hormone related cancers

Progesterone receptor (PR) is strongly associated with disease prognosis and therapeutic efficacy in hormone-related diseases such as endometriosis and breast, ovarian, and uterine cancers. Receptor status is currently determined by immunohistochemistry assays. However, noninvasive PR imaging agents could improve disease detection and help elucidate pathological molecular pathways, leading to new therapies and animal disease models. A series of water-soluble PR-targeted magnetic resonance imaging (MRI) probes were synthesized using Cu(I)-catalyzed click chemistry and evaluated in vitro and in vivo. These agents demonstrated activation of PR in vitro and preferential accumulation in PR(+) compared to PR(-) human breast cancer cells with low toxicity. In xenograft tumor models, the agents demonstrated enhanced signal intensity in PR(+) tumors compared to PR(-) tumors. The results suggest that these agents may be promising MRI probes for PR(+) diseases.

Breast imaging: A survey

Breast cancer is the second leading cause of death in women. It occurs when cells in the breast start to grow out of proportion and invade neighboring tissues or spread throughout the body. Mammography is one of the most effective and popular modalities presently used for breast cancer screening and detection. Efforts have been made to improve the accuracy of breast cancer diagnosis using different imaging modalities. Ultrasound and magnetic resonance imaging have been used to detect breast cancers in high risk patients. Recently, electrical impedance imaging and nuclear medicine techniques are also being widely used for breast cancer screening and diagnosis. In this paper, we discuss the capabilities of various breast imaging modalities.

18F-FDG PET/CT imaging in oncology

Accurate diagnosis and staging are essential for the optimal management of cancer patients. Positron emission tomography with 2-deoxy-2-[fluorine-18]fluoro-D-glucose integrated with computed tomography (18F-FDG PET/CT) has emerged as a powerful imaging tool for the detection of various cancers. The combined acquisition of PET and CT has synergistic advantages over PET or CT alone and minimizes their individual limitations. It is a valuable tool for staging and restaging of some tumors and has an important role in the detection of recurrence in asymptomatic patients with rising tumor marker levels and patients with negative or equivocal findings on conventional imaging techniques. It also allows for monitoring response to therapy and permitting timely modification of therapeutic regimens. In about 27% of the patients, the course of management is changed. This review provides guidance for oncologists/radiotherapists and clinical and surgical specialists on the use of 18F-FDG PET/CT in oncology.

Modern breast cancer detection: a technological review

Breast cancer is a serious threat worldwide and is the number two killer of women in the United States. The key to successful management is screening and early detection. What follows is a description of the state of the art in screening and detection for breast cancer as well as a discussion of new and emerging technologies. This paper aims to serve as a starting point for those who are not acquainted with this growing field.

Receptor-targeted nanoparticles for in vivo imaging of breast cancer

PURPOSE

Cell-surface receptor-targeted magnetic iron oxide nanoparticles provide molecular magnetic resonance imaging contrast agents for improving specificity of the detection of human cancer.

EXPERIMENTAL DESIGN

The present study reports the development of a novel targeted iron oxide nanoparticle using a recombinant peptide containing the amino-terminal fragment of urokinase-type plasminogen activator (uPA) conjugated to magnetic iron oxide nanoparticles amino-terminal fragment conjugated-iron oxide (ATF-IO). This nanoparticle targets uPA receptor, which is overexpressed in breast cancer tissues.

RESULTS

ATF-IO nanoparticles are able to specifically bind to and be internalized by uPA receptor-expressing tumor cells. Systemic delivery of ATF-IO nanoparticles into mice bearing s.c. and i.p. mammary tumors leads to the accumulation of the particles in tumors, generating a strong magnetic resonance imaging contrast detectable by a clinical magnetic resonance imaging scanner at a field strength of 3 tesla. Target specificity of ATF-IO nanoparticles showed by in vivo magnetic resonance imaging is further confirmed by near-IR fluorescence imaging of the mammary tumors using near-IR dye-labeled amino-terminal fragment peptides conjugated to iron oxide nanoparticles. Furthermore, mice administered ATF-IO nanoparticles exhibit lower uptake of the particles in the liver and spleen compared with those receiving nontargeted iron oxide nanoparticles.

CONCLUSIONS

Our results suggest that uPA receptor-targeted ATF-IO nanoparticles have potential as molecularly targeted, dual modality imaging agents for in vivo imaging of breast cancer.

Immunoimaging of CXCR4 expression in brain tumor xenografts using SPECT/CT

Chemokine receptor 4 (CXCR4) is expressed in a variety of cancers, including breast, brain, ovarian, and prostate. CXCR4-CXCL12 interactions are critical for tumor development, growth, and metastasis. Compared with normal tissue, neoplastic tissue (including metastases) expresses high levels of CXCR4. Previous clinical and preclinical observations suggest that CXCR4 levels could be used as a predictive marker of metastatic potential. Here we report the results of SPECT/CT of CXCR4 expression levels in experimental brain tumors using (125)I-labeled anti-CXCR4 monoclonal antibodies (mAbs).

METHODS

hCXCR4 antibody 12G5 and control IgG(2A) antibody were radiolabeled. Radio-mAbs were obtained in 40%-60% yield, with 1.4-1.9 MBq/microg specific radioactivities and greater than 95% purity. Severe combined immunodeficient mice harboring U87 xenografts were used for ex vivo biodistribution and imaging studies. Surface CXCR4 expression levels on U87 tumor-derived cells were analyzed by flow cytometry.

RESULTS

Biodistribution and imaging studies showed a specific accumulation of (125)I-12G5 in U87 tumors, with tumor-to-muscle uptake ratios reaching 15 +/- 3 at 48 h after injection. The tumor-to-tumor uptake ratio for (125)I-12G5 and (125)I-IgG(2A) was 2.5 at 48 h after injection. Flow cytometry analysis of tumor-derived cells showed a 2- to 7-fold increase in CXCR4 expression relative to inoculums, accounting for the high mAb uptake observed in the tumors.

CONCLUSION

Our data demonstrate the feasibility of imaging CXCR4 expression in experimental brain tumors. The elevated CXCR4 levels observed may have been, in part, due to the hypoxic tumor microenvironment.

Practical applications of nuclear medicine in imaging breast cancer

The rise in incidence, morbidity, and mortality of breast cancer has triggered multiple imaging efforts to detect this malignancy early, stage it accurately, and monitor it with precision in the posttherapeutic course. Among different imaging modalities, nuclear medicine provides an important contribution to the clinical management of breast cancer. This article discusses four practical applications based on the use of radionuclides in the evaluation of breast malignancy, focusing on scintimammography, preoperative tumor localization procedure using radioactive seeds, sentinel nodal scintigraphy, and F-18 fluorodeoxyglucose positron emission tomography/computed tomography.

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.

Multiparametric monitoring of tumor response to chemotherapy by noninvasive imaging

With the emerging concept of individualized cancer therapy, it becomes crucial to develop methods for the noninvasive assessment of treatment outcome. With this in mind, we designed a novel approach for the comprehensive evaluation of response to chemotherapy with the established agent doxorubicin in a preclinical breast cancer model. This approach delivers information not only about change in tumor size but also about target antigen expression. Our strategy relies on a tumor-specific contrast agent (MN-EPPT) targeting the underglycosylated MUC-1 (uMUC-1) tumor antigen, found on more than 90% of breast cancers and predictive of chemotherapeutic response. MN-EPPT consists of superparamagnetic iron oxide nanoparticles (MN) for magnetic resonance imaging, modified with Cy5.5 dye (for near-IR fluorescence optical imaging), and conjugated to peptides (EPPT), specifically recognizing uMUC-1. In vivo, treatment of mice bearing orthotopic human breast carcinomas with doxorubicin led to a reduction in tumor mass and resulted in down-regulation of uMUC-1. The tumor-specific accumulation of MN-EPPT allowed the assessment of change in tumor volume by noninvasive imaging. Furthermore, in mice injected with MN-EPPT, tumor delta-T2 was significantly reduced after treatment with doxorubicin, indicating a lower accumulation of MN-EPPT and reflecting the reduced expression of uMUC-1. With these studies, we have shown the utility of magnetic resonance imaging for the multiparametric characterization of breast tumor response to chemotherapy. This approach has the potential of significantly advancing our ability to better direct the development of molecularly targeted individualized therapy protocols because it permits the monitoring of therapy on a molecular scale.

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.

Non-natural amino acids for tumor imaging using positron emission tomography and single photon emission computed tomography

Amino acids are required nutrients for proliferating tumor cells, and amino acid transport is upregulated in many tumor types. Studies of radiolabeled amino acids in animals and humans demonstrate that amino acid based tracers have advantageous characteristics relative to 2-[(18)F]fluoro-2-deoxyglucose in certain tumors, particularly brain gliomas. Non-natural amino acids for tumor imaging generally have greater metabolic stability and can be labeled with longer-lived radionuclides for positron emission tomography and single photon emission computed tomography such as fluorine-18 and iodine-123. Amino acids enter cells via amino acid transport with varying selectivity based on their chemical structure. This review focuses on the rationale, biological basis, current status and future prospects of radiolabeled non-natural amino acids for tumor imaging and discusses various classes of these compounds including aromatic, alicyclic and alpha,alpha-dialkyl amino acids.

Molecular imaging as a tool for translating breast cancer science

The ability to measure biochemical and molecular processes underlies progress in breast cancer biology and treatment. These assays have traditionally been performed by analysis of cell culture or tissue samples. More recently, functional and molecular imaging has allowed the in vivo assay of biochemistry and molecular biology, which is highly complementary to tissue-based assays. This review briefly describes different imaging modalities used in molecular imaging and then reviews applications of molecular imaging to breast cancer, with a focus on translational work. It includes sections describing work in functional and physiological tumor imaging, imaging gene product expression, imaging the tumor microenvironment, reporter gene imaging, and cell labeling. Work in both animal models and human is discussed with an eye towards studies that have relevance to breast cancer treatment in patients.