Methodological standardization for a multi-institutional in vivo trial of localized 31P MR spectroscopy in human cancer research. In vitro and normal volunteer studies

Prospective of 31 P MR Spectroscopy in Hepatopancreatobiliary Cancer: A Systematic Review of the Literature

BACKGROUND

The incidence of liver and pancreatic cancer is rising. Patients benefit from current treatments, but there are limitations in the evaluation of (early) response to treatment. Tumor metabolic alterations can be measured noninvasively with phosphorus (³¹ P) magnetic resonance spectroscopy (MRS).

PURPOSE

To conduct a quantitative analysis of the available literature on ³¹ P MRS performed in hepatopancreatobiliary cancer and to provide insight into its current and potential for therapy (non-) response assessment.

POPULATION

Patients with hepatopancreatobiliary cancer. FIELD STRENGTH/SEQUENCE: ³¹ P MRS.

ASSESSMENT

The PubMed, EMBASE, and Cochrane library databases were systematically searched for studies published to 17 March 17, 2022. All ³¹ P MRS studies in hepatopancreatobiliary cancer reporting ³¹ P metabolite levels were included.

STATISTICAL TESTS

Relative differences in ³¹ P metabolite levels/ratios between patients before therapy and healthy controls, and the relative changes in ³¹ P metabolite levels/ratios in patients before and after therapy were determined.

RESULTS

The search yielded 10 studies, comprising 301 subjects, of whom 132 (44%) healthy volunteers and 169 (56%) patients with liver cancer of various etiology. To date, ³¹ P MRS has not been applied in pancreatic cancer. In liver cancer, alterations in levels of ³¹ P metabolites involved in cell proliferation (phosphomonoesters [PMEs] and phosphodiesters [PDEs]) and energy metabolism (ATP and inorganic phosphate [Pi]) were observed. In particular, liver tumors were associated with elevations of PME/PDE and PME/Pi compared to healthy liver tissue, although there was a broad variety among studies (elevations of 2%-267% and 21%-233%, respectively). Changes in PME/PDE in liver tumors upon therapy were substantial, yet very heterogeneous and both decreases and increases were observed, whereas PME/Pi was consistently decreased after therapy in all studies (-13% to -76%).

DATA CONCLUSION

³¹ P MRS has great potential for treatment monitoring in oncology. Future studies are needed to correlate the changes in ³¹ P metabolite levels in hepatopancreatobiliary tumors with treatment response.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 2.

Assessment of Nicotinamide Adenine Dinucleotide in Human Tissues by In Vivo Phosphorus-31 Magnetic Resonance Spectroscopic Imaging at 1.5 Tesla

As a phosphorus-containing molecule, nicotinamide adenine dinucleotide is visible by phosphorus magnetic resonance spectroscopy (31P-MRS). However, the relatively low cellular levels of its oxidised (NAD+) and reduced (NADH) forms and a significant peak overlap hinder their evaluation in live tissues. This problem is critical when using 31P-MR spectroscopic imaging, where signals are localised from limited tissue volumes. We have reported improvements in spectral resolution of 31P-MRSI of human tissues in situ using a strict optimisation of the static magnetic field (B0 shimming) and 1H-irradiation during 31P acquisition. Given this, we aimed to demonstrate if these improvements allowed us to measure the in vivo intracellular levels of NAD+ and NADH at the relatively low magnetic field of 1.5 tesla (T). Our results show the feasibility of the in vivo determination of NAD+ and NADH from relatively small volumes of human tissues studied at 1.5 T. These results are clinically relevant as the currently available systems for human use mainly operate at 1.5 or 3.0.

Comparison of three reference methods for the measurement of intracellular pH using 31P MRS in healthy volunteers and patients with lymphoma

31P magnetic resonance spectroscopy (31P MRS) can measure intracellular pH (pHi) using the chemical shift difference between pH-dependent inorganic phosphate (Pi) and a pH-independent reference peak. This study compared three different frequency reference peaks [phosphocreatine (PCr), α resonance of adenosine triphosphate (αATP) and water (using 1H MRS)] in a cohort of 10 volunteers and eight patients with non-Hodgkin's lymphoma (NHL). Well-resolved chemical shift imaging (CSI) spectra were acquired on a 1.5T scanner for muscle, liver and tumour. The pH was calculated for all volunteers and patients using the available methods. The consistency of the resulting pH was evaluated. The direct Pi–PCr method was best for those spectra with a very well-defined PCr, such as muscle (pH=7.05 ± 0.02). In liver, the Pi–αATP method gave more consistent results (pH=7.30 ± 0.06) than the calibrated water-based method (pH=7.27 ± 0.11). In NHL nodes, the measured pH using the Pi–αATP method was 7.25 ± 0.12. Given that the measured range includes some biological variation in individual patients, treatment-related changes of the order of 0.1 pH units should be detectable.

Magnetic resonance spectroscopy of cancer metabolism and response to therapy

Magnetic resonance spectroscopy allows noninvasive in vivo measurements of biochemical information from living systems, ranging from cultured cells through experimental animals to humans. Studies of biopsies or extracts offer deeper insights by detecting more metabolites and resolving metabolites that cannot be distinguished in vivo. The pharmacokinetics of certain drugs, especially fluorinated drugs, can be directly measured in vivo. This review briefly describes these methods and their applications to cancer metabolism, including glycolysis, hypoxia, bioenergetics, tumor pH, and tumor responses to radiotherapy and chemotherapy.

Molecular imaging for personalized cancer care

Molecular imaging is rapidly gaining recognition as a tool with the capacity to improve every facet of cancer care. Molecular imaging in oncology can be defined as in vivo characterization and measurement of the key biomolecules and molecularly based events that are fundamental to the malignant state. This article outlines the basic principles of molecular imaging as applied in oncology with both established and emerging techniques. It provides examples of the advantages that current molecular imaging techniques offer for improving clinical cancer care as well as drug development. It also discusses the importance of molecular imaging for the emerging field of theranostics and offers a vision of how molecular imaging may one day be integrated with other diagnostic techniques to dramatically increase the efficiency and effectiveness of cancer care.

31P MRSI and 1H MRS at 7 T: initial results in human breast cancer

This study demonstrates the feasibility of the noninvasive determination of important biomarkers of human (breast) tumor metabolism using high-field (7-T) MRI and MRS. (31) P MRSI at this field strength was used to provide a direct method for the in vivo detection and quantification of endogenous biomarkers. These encompass phospholipid metabolism, phosphate energy metabolism and intracellular pH. A double-tuned, dual-element transceiver was designed with focused radiofrequency fields for unilateral breast imaging and spectroscopy tuned for optimized sensitivity at 7 T. T(1) -weighted three-dimensional MRI and (1) H MRS were applied for the localization and quantification of total choline compounds. (31) P MRSI was obtained within 20 min per subject and mapped in three dimensions over the breast with pixel volumes of 10 mL. The feasibility of monitoring in vivo metabolism was demonstrated in two patients with breast cancer during neoadjuvant chemotherapy, validated by ex vivo high-resolution magic angle spinning NMR and compared with data from an age-matched healthy volunteer. Concentrations of total choline down to 0.4 mM could be detected in the human breast in vivo. Levels of adenosine and other nucleoside triphosphates, inorganic phosphate, phosphocholine, phosphoethanolamine and their glycerol diesters detected in glandular tissue, as well as in tumor, were mapped over the entire breast. Altered levels of these compounds were observed in patients compared with an age-matched healthy volunteer; modulation of these levels occurred in breast tumors during neoadjuvant chemotherapy. To our knowledge, this is the first comprehensive MRI and MRS study in patients with breast cancer, which reveals detailed information on the morphology and phospholipid metabolism from volumes as small as 10 mL. This endogenous metabolic information may provide a new method for the noninvasive assessment of prognostic and predictive biomarkers in breast cancer treatment.

MRS and MRSI guidance in molecular medicine: targeting and monitoring of choline and glucose metabolism in cancer

MRS and MRSI are valuable tools for the detection of metabolic changes in tumors. The currently emerging era of molecular medicine, which is shaped by molecularly targeted anticancer therapies combined with molecular imaging of the effects of such therapies, requires powerful imaging technologies that are able to detect molecular information. MRS and MRSI are such technologies that are able to detect metabolites arising from glucose and choline metabolism in noninvasive in vivo settings and at higher resolution in tissue samples. The roles played by MRS and MRSI in the diagnosis of different types of cancer, as well as in the early monitoring of the tumor response to traditional chemotherapies, are reviewed. The emerging roles of MRS and MRSI in the development and detection of novel targeted anticancer therapies that target oncogenic signaling pathways or markers in choline or glucose metabolism are discussed.

Molecular Imaging in Breast Cancer - Potential Future Aspects

SUMMARY: Molecular imaging aims to visualize and quantify biological, physiological, and pathological processes at cellular and molecular levels. Recently, molecular imaging has been introduced into breast cancer imaging. In this review, we will present a survey of the molecular imaging techniques that are either clinically available or are being introduced into clinical imaging. We will discuss nuclear imaging and multiparametric magnetic resonance imaging as well as the combined application of molecular imaging in the assessment of breast lesions. In addition, we will briefly discuss other evolving molecular imaging techniques, such as phosphorus magnetic resonance spectroscopic imaging and sodium imaging.

In vivo 31P spectroscopy by fully adiabatic extended image selected in vivo spectroscopy: a comparison between 3 T and 7 T

An improved image selected in vivo spectroscopy (ISIS) sequence for localized (31)P magnetic resonance spectroscopy at 7 T was developed. To reduce errors in localization accuracy, adiabatic excitation, gradient offset independent adiabatic inversion pulses, and a special extended ISIS ordering scheme were used. The localization accuracy of extended ISIS was investigated in phantoms. The possible spectral quality and reproducibility in vivo was explored in a volunteer (brain, muscle, and liver). A comparison between 3 T and 7 T was performed in five volunteers. Adiabatic extended ISIS provided high spectral quality and accurate localization. The contamination in phantom experiments was only ∼5%, even if a pulse repetition time ∼ 1.2·T(1) was chosen to maximize the signal-to-noise ratio per unit time. High reproducibility was found in the calf muscle for 2.5 cm isotropic voxels at 7 T. When compared with 3 T, localized (31)P magnetic resonance spectroscopy in the human calf muscle at 7 T provided ∼3.2 times higher signal-to-noise ratio (as judged from phosphocreatine peak amplitude in frequency domain after matched filtering). At 7 T, extended ISIS allowed the performance of high-quality localized (31)P magnetic resonance spectroscopy in a short measurement time (∼3 to 4 min) and isotropic voxel sizes of ∼2.5 to 3 cm. With such short measurement times, localized (31)P magnetic resonance spectroscopy has the potential to be applied not only for clinical research but also for routine clinical practice.

Use of the 1-mm micro-probe for metabolic analysis on small volume biological samples

Endogenous metabolites are promising diagnostic end-points in cancer research. Clinical application of high-resolution NMR spectroscopy is often limited by extremely low volumes of human specimens. In the present study, the use of the Bruker 1-mm high-resolution TXI micro-probe was evaluated in the elucidation of metabolic profiles for three different clinical applications with limited sample sizes (body fluids, isolated cells and tissue biopsies). Sample preparation and (1)H-NMR metabolite quantification protocols were optimized for following oncology-oriented applications: (i) to validate the absolute concentrations of citrate and spermine in human expressed prostatic specimens (EPS volumes 5 to 10 microl: prostate cancer application); (ii) to establish the metabolic profile of isolated human lymphocytes (total cell count 4 x 10(6): chronic myelogenous leukaemia application); (iii) to assess the metabolic composition of human head-and-neck cancers from mouse xenografts (biopsy weights 20 to 70 mg: anti-cancer treatment application). In this study, the use of the Bruker 1-mm micro-probe provides a convenient way to measure and quantify endogenous metabolic profiles of samples with a very low volume/weight/cell count.

Molecular imaging of cancer: MR spectroscopy and beyond

Proton magnetic resonance spectroscopic imaging is a non-invasive diagnostic tool for the investigation of cancer metabolism. As an adjunct to morphologic and dynamic magnetic resonance imaging, it is routinely used for the staging, assessment of treatment response, and therapy monitoring in brain, breast, and prostate cancer. Recently, its application was extended to other cancerous diseases, such as malignant soft-tissue tumours, gastrointestinal and gynecological cancers, as well as nodal metastasis. In this review, we discuss the current and evolving clinical applications of proton magnetic resonance spectroscopic imaging. In addition, we will briefly discuss other evolving techniques, such as phosphorus magnetic resonance spectroscopic imaging, sodium imaging and diffusion-weighted imaging in cancer assessment.

Proton and phosphorous MR spectroscopy in squamous cell carcinomas of the head and neck

RATIONALE AND OBJECTIVES

Phosphorous magnetic resonance spectroscopy ((31)P MRS) has been used to evaluate and predict treatment response in squamous cell carcinoma of the head and neck (HNSCC). Several studies have also shown the potential of proton MRS ((1)H MRS) in assessing response in HNSCC. In view of the inherent limitations associated with performing (31)P MRS in clinical settings, the current study was performed to explore whether (1)H MRS could provide similar or complementary metabolic information in HNSCC.

MATERIALS AND METHODS

Fifteen patients with HNSCC underwent pretreatment magnetic resonance imaging. Both (1)H MRS and (31)P MRS were performed on viable solid parts of the metastatic lymph nodes of these patients. Peak areas of total choline (tCho) and unsuppressed water as observed on (1)H MRS and phosphomonoester (PME) and beta-nucleotide triphosphate (beta-NTP) on (31)P MRS were computed. Pearson's correlation coefficient was used to correlate the tCho/water and PME/beta-NTP ratios.

RESULTS

In all patients, the metastatic nodes appeared hyperintense on T2-weighted images and hypointense on T1-weighted images with variable signal intensity. A prominent resonance of tCho on (1)H MRS and a resonance of PME on (31)P MRS from the metastatic nodes of all patients were observed. A moderate correlation of 0.31 was observed between tCho/water and PME/beta-NTP (P > .05).

CONCLUSIONS

The biochemical pathways involved in (1)H MRS of tCho may be different from the phospholipid metabolites seen on (31)P MRS of head and neck cancers, and thus the two MRS techniques may be complementary to each other.

Magnetic resonance spectroscopy of living tissues

The comprehensive work of both clinical and basic science colleagues has demonstrated a clear proof of concept for "in vitro discovered- in vivo validated" biomarkers in translational metabolic profiling research using magnetic resonance techniques. Major tissue metabolites (initially discovered by high-resolution in vitro techniques on cancer specimens) can be translated into in vivo protocols based on noninvasive magnetic resonance spectroscopy (MRS). Using (1)H- and (31)P-MRS on living animals or patients, a decrease in citrate and polyamines in prostate cancer, an increase of cholines in breast cancer, as well as a decreased NAA and an increased lactate in gliomas during cancer progression can be assessed noninvasively. MRS can be used to follow up conventional cytotoxic as well as targeted anticancer therapies, which has been extensively done in animal models of cancer. This review focuses on applications and protocol development for in vivo (1)H- and (31)P-MRS on small animal models as well as on larger animals in cancer research, diagnosis, and treatment.

In vivo MRS markers of response to CHOP chemotherapy in the WSU-DLCL2 human diffuse large B-cell lymphoma xenograft

To identify 1H-MRS molecular biomarkers of early clinical therapeutic response in non-Hodgkin's lymphoma, an in vivo longitudinal study was performed on human non-Hodgkin's diffuse large B-cell lymphoma xenografts (WSU-DLCL2) grown in the flanks of female SCID mice. 31P-MRS measurements, which have been demonstrated to be prognostic clinical indices of response (Arias-Mendoza et al. Acad. Radiol. 2004; 11: 368-376) but which provide lower spatial resolution, were included for comparison. The animals received CHOP (cyclophosphamide, hydroxydoxorubicin, oncovin and prednisone) chemotherapy for three 1-week cycles, resulting in stable disease based on tumor volume. Localization of total choline and phosphorus metabolites in vivo was achieved with stimulated echo acquisition mode and image selected in vivo spectroscopy sequences, respectively. Significant decreases in lactate were detected by the selective multiple quantum coherence spectral editing technique after the first cycle of CHOP, whereas total choline and the phosphomonoester/nucleoside triphosphate ratio did not change until the third cycle. Ex vivo extract MRS of tumors corroborated the in vivo results. Histological staining with antibodies to Ki67 revealed a decrease in proliferation rate in CHOP-treated tumors that coincided with the decrease in lactate. This study demonstrates the utility of lactate as an early proliferation-sensitive indicator of therapeutic response in a mouse model of non-Hodgkin's lymphoma and serves as a basis for future clinical implementation of these methods.

Musculoskeletal spectroscopy

Magnetic resonance spectroscopy (MRS) of skeletal muscle has been successfully applied by physiologists over several decades, particularly for studies of high-energy phosphates (by (31)P-MRS) and glycogen (by (13)C-MRS). Unfortunately, the observation of these heteronuclei requires equipment that is typically not available on clinical MR scanners, such as broadband capability and a second channel for decoupling and nuclear Overhauser enhancement (NOE). On the other hand, (1)H-MR spectra of skeletal muscle can be acquired on many routine MR systems and also provide a wealth of physiological information. In particular, studies of intramyocellular lipids (IMCL) attract physiologists and endocrinologists because IMCL levels are related to insulin resistance and thus can lead to a better understanding of major health problems in industrial countries. The combination of (1)H-, (13)C-, and (31)P-MRS gives access to the major long- and short-term energy sources of skeletal muscle. This review summarizes the technical aspects and unique MR-methodological features of the different nuclei. It reviews clinical studies that employed MRS of one or more nuclei, or combinations of MRS with other MR modalities. It also illustrates that MR spectra contain additional physiological information that is not yet used in routine clinical applications.

MR in oncology drug development

This article reviews the use of MR in preclinical and clinical experiments to aid drug development. In particular it concentrates on the use of MR to study tumor microvasculature following treatment with anti-vascular agents and the use of MRS to study tumor metabolism following treatment with a variety of anti-cancer agents. The advantages and disadvantages of a variety of techniques including contrast- and noncontrast-enhanced methods are discussed and the data from clinical trials using these techniques are reviewed. Despite the consensus documents produced to date for both dynamic contrast-enhanced MRI and MRS, most of the trials reported used alternative methods, and different nomenclature for the MR parameters used. This continues to inhibit the comparison between novel therapeutics and between different trials with the same compound. Comprehensive data from multicenter trials on the reproducibility of techniques is still lacking in the literature and the implications of the available data on clinical trial design is also discussed.

Magnetic resonance spectroscopy (MRS) in the investigation of cancer at The Royal Marsden Hospital and The Institute of Cancer Research

Developments in magnetic resonance spectroscopy (MRS) at The Royal Marsden Hospital and The Institute of Cancer Research are reviewed in the context of preceding developments in nuclear magnetic resonance (NMR) and MRS, and some of the early developments in this field, particularly those leading to human measurements. The early development of technology, and associated techniques for human measurement and assessment will be discussed, with particular reference to experience at out institutions. Applications using particular nuclei will then be described and related to other experimental work where appropriate. Contributions to the development of MRS that have been published in Physics in Medicine and Biology will be discussed.

In vivo 31P MR spectral patterns and reproducibility in cancer patients studied in a multi-institutional trial

The standardization and reproducibility of techniques required to acquire anatomically localized 31P MR spectra non-invasively while studying tumors in cancer patients in a multi-institutional group at 1.5 T are reported. This initial group of patients was studied from 1995 to 2000 to test the feasibility of acquiring in vivo localized 31P MRS in clinical MR spectrometers. The cancers tested were non-Hodgkin's lymphomas, sarcomas of soft tissue and bone, breast carcinomas and head and neck carcinomas. The best accrual and spectral quality were achieved with the non-Hodgkin's lymphomas. The initial analysis of the spectral values of the sum of phosphoethanolamine plus phosphocholine normalized by the content of nucleotide triphosphates in a homogeneous sample of 32 NHL patients studied by in vivo (31)P MRS showed good reproducibility among different institutions. No statistical differences were found between the institution with the largest number of cases accrued and the rest of the multi-institutional NHL data (2.28 +/- 0.64, mean +/- standard error; n = 17, vs 2.08 +/- 0.14, n = 15). The preliminary data reported demonstrate that the institutions involved in this trial are obtaining reproducible 31P MR spectroscopic data non-invasively from human tumors. This is a fundamental prerequisite for the international cooperative group to be able to demonstrate the clinical value of the normalized determination of phosphoethanolamine plus phosphocholine by 31P MRS as predictor for treatment response in cancer patients.

Liver regeneration in humans is characterized by significant changes in cellular phosphorus metabolism: assessment using proton-decoupled 31P-magnetic resonance spectroscopic imaging

In the present study we applied proton-decoupled 31P magnetic resonance spectroscopic imaging (MRSI) to noninvasively assess liver metabolism in patients who had undergone a partial hepatectomy (PH). Proton-decoupled 31P chemical shift imaging was performed in 47 patients 2-28 days following major hepatectomy, and the results were compared with those from eight control subjects. All studies were performed on a 1.5T MR imager (General Electric, Milwaukee, WI) equipped with a stand-alone proton decoupler. A 31P-1H resonator pair was used for data acquisition, and 31P data were obtained in 34 min. Liver regeneration was characterized by increases in phosphoethanolamine (PE), and decreases in nucleoside triphosphates (NTP), glycerophosphoethanolamine (GPE), and glycerophosphocholine (GPC). These alterations were most marked 48-72 hr after hepatectomy and returned to baseline within 3 weeks. The level of PE measured by MRSI was also found to depend on the percentage of liver that was removed, while changes in levels of cellular high energy phosphates were independent of the size of liver resection. Implementation of proton-decoupling was critical for assessing individual phosphomonoester and phosphodiester components. This study demonstrates that 31P MRSI can be used to assess metabolic changes in humans during liver regeneration, and may be useful for assessing derangement of the regenerative process or guiding adjuvant chemotherapies.