Pathology of Barrett's esophagus by proton magnetic resonance spectroscopy and a statistical classification strategy

Candidate serum metabolite biomarkers for differentiating gastroesophageal reflux disease, Barrett's esophagus, and high-grade dysplasia/esophageal adenocarcinoma

INTRODUCTION/OBJECTIVES

Incidence of esophageal adenocarcinoma (EA), an often fatal cancer, has increased sharply over recent decades. Several important risk factors (reflux, obesity, smoking) have been identified for EA and its precursor, Barrett's esophagus (BE), but a key challenge remains identifying individuals at highest risk, since most with reflux do not develop BE, and most with BE do not progress to cancer. Metabolomics represents an emerging approach for identifying novel biomarkers associated with cancer development.

METHODS

We used targeted liquid chromatography-mass spectrometry (LC-MS) to profile 57 metabolites in 322 serum specimens derived from individuals with gastroesophageal reflux disease (GERD), BE, high-grade dysplasia (HGD), or EA, drawn from two well-annotated epidemiologic parent studies.

RESULTS

Multiple metabolites differed significantly (P<0.05) between BE versus GERD (n=9), and between HGD/EA versus BE (n=4). Several top candidates (FDR q≤0.15), including urate, homocysteine, and 3-nitrotyrosine, are linked to inflammatory processes, which may contribute to BE/EA pathogenesis. Multivariate modeling achieved moderate discrimination between HGD/EA and BE (AUC=0.75), with less pronounced separation for BE versus GERD (AUC=0.64).

CONCLUSION

Serum metabolite differences can be detected between individuals with GERD versus BE, and between those with BE versus HGD/EA, and may help differentiate patients at different stages of progression to EA.

Metabolomic Evidence for a Field Effect in Histologically Normal and Metaplastic Tissues in Patients with Esophageal Adenocarcinoma

Patients with Barrett's esophagus (BO) are at increased risk of developing esophageal adenocarcinoma (EAC). Most Barrett's patients, however, do not develop EAC, and there is a need for markers that can identify those most at risk. This study aimed to see if a metabolic signature associated with the development of EAC existed. For this, tissue extracts from patients with EAC, BO, and normal esophagus were analyzed using ¹H nuclear magnetic resonance. Where possible, adjacent histologically normal tissues were sampled in those with EAC and BO. The study included 46 patients with EAC, 7 patients with BO, and 68 controls who underwent endoscopy for dyspeptic symptoms with normal appearances. Within the cancer cohort, 9 patients had nonneoplastic Barrett's adjacent to the cancer suitable for biopsy. It was possible to distinguish between histologically normal, BO, and EAC tissue in EAC patients [area under the receiver operator curve (AUROC) 1.00, 0.86, and 0.91] and between histologically benign BO in the presence and absence of EAC (AUROC 0.79). In both these cases, sample numbers limited the power of the models. Comparison of histologically normal tissue proximal to EAC versus that from controls (AUROC 1.00) suggests a strong field effect which may develop prior to overt EAC and hence be useful for identifying patients at high risk of developing EAC. Excellent sensitivity and specificity were found for this model to distinguish histologically normal squamous esophageal mucosa in EAC patients and healthy controls, with 8 metabolites being very significantly altered. This may have potential diagnostic value if a molecular signature can detect tissue from which neoplasms subsequently arise.

Study of metabonomic profiles of human esophageal carcinoma by use of high-resolution magic-angle spinning 1H NMR spectroscopy and multivariate data analysis

Esophageal carcinoma (EC) is one of the most common malignant tumors. EC survival has remained disappointingly low because of the high malignancy of esophageal cancer and the lack of obvious clinical symptoms at an early stage. Early diagnosis is often difficult because the small tumor nodules are frequently missed. Metabonomics based on high-resolution magic-angle spinning (HRMAS) NMR has been popular for tumor detection because it is highly sensitive, provides rich biochemical information and requires no sample pretreatment. (1)H HRMAS spectra of non-involved adjacent esophageal tissues and of well differentiated and moderately differentiated esophageal carcinoma tumors were recorded and analyzed by use of multivariate and statistical analysis techniques. Moderately differentiated EC tumors were found to have increased total choline, alanine, and glutamate and reduced creatine, myo-inositol, and taurine compared with non-involved adjacent tissues. Moreover, clear differences between the metabonomic profiles of EC tissues enabled tumor differentiation. Furthermore, the integral Gly/MI ratio for samples of different tissue types were statistically significantly different; this was sufficient both for distinguishing non-involved tissues from esophageal carcinoma and for classification of well differentiated and moderately differentiated EC tumors.

Diagnostic value of 8.5 T magnetic resonance spectroscopy of benign and malignant skin lesion biopsies

Proton magnetic resonance spectroscopy at 8.5 T ex vivo was used to investigate skin lesions for metabolic signatures to predict malignancy or indicate malignant potential. Magnetic resonance spectroscopy was performed on biopsy tissue obtained from 63 skin lesions and five melanoma metastases from 55 patients. Samples were grouped and compared according to five clinically significant distinctions: melanoma (n=38) or nonmelanoma (n=30), primary melanoma (n=33) or secondary melanoma (involved nodes and distant metastases, n=5), primary melanoma (n=33) or nevi (n=8), malignant (n=46) or nonmalignant (n=22), and melanocytic (n=46) or nonmelanocytic (n=22). In all comparisons, the average magnetic resonance spectrum of each class lay within 1 standard deviation of the average spectrum of the other class. There was a higher average choline metabolite signal intensity in melanoma-containing biopsies compared with nonmelanoma biopsies. Discriminant analysis based on the intensity of the choline resonance alone achieved 69% accuracy in separation of melanoma and nonmelanoma tissue. Inclusion of other metabolite resonances in the analysis did not increase discrimination accuracy. Tissue heterogeneity in conventionally collected full thickness skin biopsies and possible biochemical variance within individual tissue types limit classification accuracy using the methods and magnetic field strength that were earlier reported to provide accurate discrimination in other cancer types.

Detecting colorectal cancer by 1H magnetic resonance spectroscopy of fecal extracts

Colorectal cancer is one of the most common cancers in the western world. Its early detection has been found to improve the prognosis of the patient, providing a wide window of opportunity for successful therapeutic interventions. However, current diagnostic techniques all have some limitations; there is a need to develop a better technique for routine screening purposes. We present a new methodology based on magnetic resonance spectroscopy of fecal extracts for the non-invasive detection of colorectal cancer. Five hundred twenty-three human subjects (412 with no colonic neoplasia and 111 with colorectal cancer, who were scheduled for colonoscopy or surgery) were recruited to donate a single sample of stool. One-dimensional (1)H magnetic resonance spectroscopy (MRS) experiments were performed on the supernatant of aqueous dispersions of the stool samples. Using a statistical classification strategy, several multivariate classifiers were developed. Applying the preprocessing, feature selection and classifier development stages of the Statistical Classification Strategy led to approximately 87% average balanced sensitivity and specificity for both training and monitoring sets, improving to approximately 92% when only crisp results, i.e. class assignment probabilities > or =75%, are considered. These results indicate that (1)H magnetic resonance spectroscopy of human fecal extracts, combined with appropriate data analysis methodology, has the potential to detect colorectal neoplasia accurately and reliably, and could be a useful addition to the current screening tools.

Targeting regions with highest lipid content on MR spectroscopy may improve diagnostic yield in stereotactic biopsy

Gliomas are heterogeneous brain tumors and prognosis and treatment are dependent on the highest histological grade present. Stereotactic biopsy is associated with an inherent risk of sampling error. Magnetic resonance spectroscopy (MRS) uses clinical MR scanners to provide chemical in addition to conventional information. MRS studies in brain tumors have found increased levels of choline-containing compounds (Cho) and decreased levels of N-acetylaspartate (NAA), creatine (Cr) and phosphocreatine (PCr) which are all associated with increased grade of glioma. We propose the use of MRS-guided stereotactic biopsy of astrocytomas to increase diagnostic yield and reduce the sampling error rate. MRS was performed on two patients undergoing stereotactic biopsy for suspected astrocytoma. Spectral peak heights of the metabolites Cho at 3.2 parts per million (ppm) chemical shift, NAA at 2.0 ppm and lipid (Lip) at 1.2 ppm, were measured. Biopsy targets were selected from the voxels with the highest Cho/NAA and normalised against Cho levels in the contralateral normal tissue, as well as those with highest lipid content. The biopsies were taken and tissue diagnosis was obtained via standard histological techniques. Histological grade was found to be different in one case: the region with a high Lip/Cr and Cho/NAA ratios showed glioblastoma, whereas the region with high Cho/NAA but low Lip/Cr ratios showed anaplastic astrocytoma. The second patient had high Cho/NAA ratio but low Lip/Cr ratio in both targets and the histology revealed anaplastic astrocytoma in both samples. MRS is a useful biomedical imaging tool for diagnosing and grading astrocytomas. Targeting regions with highest lipid content can potentially improve the diagnostic yield and minimize sampling error in stereotactic biopsy.

Proton spectroscopy provides accurate pathology on biopsy and in vivo

In the last 25 years, MR spectroscopy (MRS) has moved from being a basic research tool into routine clinical use. The spectroscopy method reports on those chemicals that are mobile on the MR time scale. Many of these chemicals reflect specific pathological processes but are complicated by the fact that many chemicals change at one time. There are currently two clinical applications for spectroscopy. The first is in the pathology laboratory, where it can be an adjunct to, and in some cases replacement, for difficult pathologies like Barrett's esophagus and follicular adenoma of the thyroid. The spectroscopy method on a breast biopsy can also report on prognostic indicators, including the potential for spread, from information present in the primary tumor alone. The second application for spectroscopy is in vivo to provide a preoperative diagnosis and this is now achievable for several organs including the prostate. The development of spectroscopy for clinical purposes has relied heavily on the serially-sectioned histopathology to confirm the high accuracy of the method. The combination of in vivo MRI, in vivo MRS, and ex vivo MRS on biopsy samples offers a modality of very high accuracy for preoperative diagnosis and provision of prognostic information for human cancers.

Magnetic resonance in surgical oncology: II - literature review

Ex vivo and in vivo applications of magnetic resonance spectroscopy have been developed which aid in distinguishing malignant from normal tissues. Studies of breast, colon, cervix, oesophageal and prostate cancer reveal both the successes and failings of present technology. Verification that these non-invasive tests might supplant conventional histology in obtaining spatial diagnostic and chemical prognostic information remains for the time being illusive.

Melanoma Metastases in Regional Lymph Nodes Are Accurately Detected by Proton Magnetic Resonance Spectroscopy of Fine-Needle Aspirate Biopsy Samples

BACKGROUND

Nonsurgical assessment of sentinel nodes (SNs) would offer advantages over surgical SN excision by reducing morbidity and costs. Proton magnetic resonance spectroscopy (MRS) of fine-needle aspirate biopsy (FNAB) specimens identifies melanoma lymph node metastases. This study was undertaken to determine the accuracy of the MRS method and thereby establish a basis for the future development of a nonsurgical technique for assessing SNs.

METHODS

FNAB samples were obtained from 118 biopsy specimens from 77 patients during SN biopsy and regional lymphadenectomy. The specimens were histologically evaluated and correlated with MRS data. Histopathologic analysis established that 56 specimens contained metastatic melanoma and that 62 specimens were benign. A linear discriminant analysis-based classifier was developed for benign tissues and metastases.

RESULTS

The presence of metastatic melanoma in lymph nodes was predicted with a sensitivity of 92.9%, a specificity of 90.3%, and an accuracy of 91.5% in a primary data set. In a second data set that used FNAB samples separate from the original tissue samples, melanoma metastases were predicted with a sensitivity of 87.5%, a specificity of 90.3%, and an accuracy of 89.1%, thus supporting the reproducibility of the method.

CONCLUSIONS

Proton MRS of FNAB samples may provide a robust and accurate diagnosis of metastatic disease in the regional lymph nodes of melanoma patients. These data indicate the potential for SN staging of melanoma without surgical biopsy and histopathological evaluation.

In vitro 1H-magnetic resonance spectroscopy of Barrett's esophageal mucosa using magic angle spinning techniques

OBJECTIVES

In vitro proton magnetic resonance spectroscopy (MRS) allows changes in cell membrane lipid structure associated with dysplasia and malignant transformation to be investigated. Magic angle spinning (MAS) MRS allows small esophageal tissue specimens to be studied directly without the need to extract the tissue, but it is not known how intact the tissue architecture remains after MAS. We report the first prospective MAS MRS study of Barrett's esophagus using endoscopic biopsies with direct histological correlation.

METHODS

Biopsies were obtained during surveillance esophagoscopy from Barrett's epithelium and adjacent normal squamous epithelium in 16 patients (34 samples). High-resolution MAS MRS was performed at 500 MHz. Following MRS, the histology was evaluated. A further, separate group of 14 biopsies were examined histologically to assess architectural damage caused by tissue preservation alone.

RESULTS

For squamous and Barrett's epithelium, respectively, metabolite ratios of choline-containing compounds to creatine plus phosphocreatine (Cho/Cr) were 1.99 and 5.65 (P < 10) and methyl lipid to creatine plus phosphocreatine ratios (lipid-CH3/Cr) were 4.07 and 7.4 (P < 10). There was no significant difference in histological preservation between the squamous and Barrett's mucosa without MRS (z = 0.67, P = 0.61), but significant differences were found post-MAS MRS (z = 4.06, P < 0.0001).

CONCLUSIONS

Squamous and Barrett's epithelium can be distinguished metabolically, based on Cho/Cr and lipid-CH3/Cr ratios. Although MAS does affect the histological architecture in Barrett's epithelium, compared with squamous epithelium, direct histological assessment was possible in the majority of samples.

Optical detection and eradication of dysplastic Barrett's esophagus

Dysplastic Barrett's esophagus is a condition that offers multiple diagnostic and therapeutic challenges. The diagnosis of dysplasia within Barrett's esophagus currently relies on periodic endoscopic surveillance with multiple biopsies, a methodology limited by random sampling error, inconsistent histopathologic interpretation and delay in diagnosis. Optical spectroscopic and imaging techniques have the potential to identify dysplastic or early neoplastic lesions in real-time. These diagnostic modalities are needed to enhance the endoscopic surveillance of Barrett's esophagus in the future as well as help to define lesions for endoscopic therapy. Esophagectomy has been the standard of care for Barrett's esophagus with high-grade dysplasia although it is a procedure associated with significant morbidity and mortality. Minimally invasive endoscopic ablative therapies are attractive and less morbid alternatives to esophagectomy, with promising results obtained from the use of light-activated drugs (i.e., photodynamic therapy). The combination of novel optical diagnostic techniques and therapies will provide the endoscopist with much needed tools that can considerably enhance the management of patients with Barrett's esophagus. This article reviews the current status and future prospects of optical-based modalities for diagnosis and therapy of dysplastic Barrett's esophagus.

Pathologic characterization of human prostate tissue with proton MR spectroscopy

PURPOSE

To assess the accuracy of magnetic resonance (MR) spectroscopy in documenting the chemical features of human prostate tissue and to ascertain if there are chemical criteria of diagnostic importance.

MATERIALS AND METHODS

Seventy-seven prostate tissue specimens (peripheral zone, n = 61; transitional zone, n = 16) from 43 patients were analyzed with MR spectroscopy. Histologic features were compared with MR spectroscopic data. Statistical analysis was undertaken with analysis of variance and computer software.

RESULTS

Histologically identified carcinomas were determined by using MR spectroscopy with a sensitivity of 100% and a specificity of 94%. Histologically benign tissue from patients without carcinoma of the prostate was distinguished from malignant tissue with a sensitivity of 100% and a specificity of 94%. When benign specimens from patients with cancer elsewhere in the prostate were included in the database, MR spectroscopy helped distinguish benign prostatic hyperplasia from adenocarcinoma with a sensitivity of 97% and specificity of 88%. Depleted citrate and elevated choline levels alone were not accurate markers of malignancy, since citrate levels remain high when a small amount of malignant disease is present. Carcinomas missed at routine histologic examination were identified with MR spectroscopy and confirmed with specialized, nonstandard histologic examination.

CONCLUSION

By comparing the intensity of resonances assigned to choline, creatine, lipid, and lysine, MR spectroscopy can depict prostate carcinoma with a high degree of sensitivity and specificity. Citrate and choline resonances alone are not sufficiently accurate markers for distinguishing between various patterns of prostatic disease.