Functional lymphatic collectors in breast cancer-related lymphedema arm

Lymphatic-draining nanoparticles deliver Bay K8644 payload to lymphatic vessels and enhance their pumping function

Dysfunction of collecting lymphatic vessel pumping is associated with an array of pathologies. S-(-)-Bay K8644 (BayK), a small-molecule agonist of L-type calcium channels, improves vessel contractility ex vivo but has been left unexplored in vivo because of poor lymphatic access and risk of deleterious off-target effects. When formulated within lymph-draining nanoparticles (NPs), BayK acutely improved lymphatic vessel function, effects not seen from treatment with BayK in its free form. By preventing rapid drug access to the circulation, NP formulation also reduced BayK's dose-limiting side effects. When applied to a mouse model of lymphedema, treatment with BayK formulated in lymph-draining NPs, but not free BayK, improved pumping pressure generated by intact lymphatic vessels and tissue remodeling associated with the pathology. This work reveals the utility of a lymph-targeting NP platform to pharmacologically enhance lymphatic pumping in vivo and highlights a promising approach to treating lymphatic dysfunction.

Systematic Review of Magnetic Resonance Lymphangiography From a Technical Perspective

BACKGROUND

Clinical examination and lymphoscintigraphy are the current standard for investigating lymphatic function. Magnetic resonance imaging (MRI) facilitates three-dimensional (3D), nonionizing imaging of the lymphatic vasculature, including functional assessments of lymphatic flow, and may improve diagnosis and treatment planning in disease states such as lymphedema.

PURPOSE

To summarize the role of MRI as a noninvasive technique to assess lymphatic drainage and highlight areas in need of further study.

STUDY TYPE

Systematic review.

POPULATION

In October 2019, a systematic literature search (PubMed) was performed to identify articles on magnetic resonance lymphangiography (MRL).

FIELD STRENGTH/SEQUENCE

No field strength or sequence restrictions.

ASSESSMENT

Article quality assessment was conducted using a bespoke protocol, designed with heavy reliance on the National Institutes of Health quality assessment tool for case series studies and Downs and Blacks quality checklist for health care intervention studies.

STATISTICAL TESTS

The results of the original research articles are summarized.

RESULTS

From 612 identified articles, 43 articles were included and their protocols and results summarized. Field strength was 1.5 or 3.0 T in all studies, with 25/43 (58%) employing 3.0 T imaging. Most commonly, imaging of the peripheries, upper and lower limbs including the pelvis (32/43, 74%), and the trunk (10/43, 23%) is performed, including two studies covering both regions. Imaging protocols were heterogenous; however, T2 -weighted and contrast-enhanced T1 -weighted images are routinely acquired and demonstrate the lymphatic vasculature. Edema, vessel, quantity and morphology, and contrast uptake characteristics are commonly reported indicators of lymphatic dysfunction.

DATA CONCLUSION

MRL is uniquely placed to yield large field of view, qualitative and quantitative, 3D imaging of the lymphatic vasculature. Despite study heterogeneity, consensus is emerging regarding MRL protocol design. MRL has the potential to dramatically improve understanding of the lymphatics and detect disease, but further optimization, and research into the influence of study protocol differences, is required before this is fully realized.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 2.

A systematic review of magnetic resonance lymphography for the evaluation of peripheral lymphedema

OBJECTIVE

Visualization of the lymphatic system is necessary for both early diagnosis and associated treatments. A promising imaging modality is magnetic resonance lymphography (MRL). The aim of this review was to summarize different MRL protocols, to assess the clinical value in patients with peripheral lymphedema, and to define minimal requirements necessary for visualization of lymphatics.

METHODS

A systematic literature search was conducted in PubMed, Embase, and the Cochrane Library in December 2018. Studies performing MRL in patients with peripheral lymphedema or healthy participants were included. Study design, population, etiology, duration of lymphedema, clinical staging, contrast agent, dose, injection site, and technical magnetic resonance imaging details were analyzed. No meta-analyses were performed because of different study aims and heterogeneity of the study populations.

RESULTS

Twenty-five studies involving 1609 patients with both primary lymphedema (n = 669) and secondary lymphedema (n = 657) were included. Upper and lower limbs were examined in 296 and 602 patients, respectively. Twenty-two studies used a gadolinium-based contrast agent that was injected intracutaneously or subcutaneously in the interdigital web spaces. Contrast-enhanced T1-weighted combined with T2-weighted protocols were most frequently used. T1-weighted images showed lymphatics in 63.3% to 100%, even in vessels with a diameter of ≥0.5 mm. Dermal backflow and a honeycomb pattern were clearly recognized.

CONCLUSIONS

MRL identifies superficial lymphatic vessels with a diameter of ≥0.5 mm with high sensitivity and specificity and accurately shows abnormal lymphatics and lymphatic drainage patterns. Therefore, MRL could be of clinical value in both early and advanced stages of peripheral lymphedema. Minimum requirements of an MRL protocol should consist of a gadolinium-based contrast-enhanced T1-weighted gradient-recalled echo sequence combined with T2-weighted magnetic resonance imaging, with acquisition at least 30 minutes after injection of contrast material.

Correlation between superficial and deep lymphatic systems using magnetic resonance lymphangiography in breast cancer-related lymphedema: Clinical implications

BACKGROUND

Magnetic resonance lymphangiography (MRL) has increased our knowledge of lymphatic anatomy and lymphedema pathophysiology and improved the efficacy of microsurgical procedures to manage peripheral lymphedema. The aim of this study is to investigate the ability of MRL to detect communications between superficial and deep lymphatic systems in breast cancer-related lymphedema (BRCL) and to investigate whether these communications could preserve lymphatic drainage of the hand.

METHODS

Between 2008 and 2017 we used MRL imaging in 59 women with BCRL. Lymphedema of the arm and hand was detected in 30 patients while the hand was spared in 29. Using axial and coronal MRL reconstruction images we investigated the existence of any communication between the superficial and deep lymphatic systems.

RESULTS

Among the 29 patients with spared hand, MRL revealed that 24 had at least one communicating lymphatic perforator at the wrist region (p < 0.001). Lymphatic flow at the axilla was clearly visualized in 16 of the 29 patients (55.2%), no perforating lymphatic vessels were detected in the group with lymphedema in the hand (30 patients).

CONCLUSIONS

Communications between the deep and superficial lymphatic systems at the wrist region in BCRL patients without hand lymphedema should be considered when planning microsurgical lymphatic procedures at the wrist and in postoperative compression therapy.

A novel mouse tail lymphedema model for observing lymphatic pump failure during lymphedema development

It has been suggested that many forms of secondary lymphedema in humans are driven by a progressive loss of lymphatic pump function after an initial risk-inducing event. However, the link between pump failure and disease progression has remained elusive due to experimental challenges in the clinical setting and a lack of adequate animal models. Using a novel surgical model of lymphatic injury, we track the adaptation and functional decline of the lymphatic network in response to surgery. This model mimics the histological hallmarks of the typical mouse tail lymphedema model while leaving an intact collecting vessel for analysis of functional changes during disease progression. Lymphatic function in the intact collecting vessel negatively correlated with swelling, while a loss of pumping pressure generation remained even after resolution of swelling. By using this model to study the role of obesity in lymphedema development, we show that obesity exacerbates acquired lymphatic pump failure following lymphatic injury, suggesting one mechanism through which obesity may worsen lymphedema. This lymphatic injury model will allow for future studies investigating the molecular mechanisms leading to lymphedema development.

Magnetic Resonance Imaging-Based Assessment of Breast Cancer-Related Lymphoedema Tissue Composition

OBJECTIVES

The aim of this study was to propose a magnetic resonance imaging acquisition and analysis protocol that uses image segmentation to measure and depict fluid, fat, and muscle volumes in breast cancer-related lymphoedema (BCRL). This study also aims to compare affected and control (unaffected) arms of patients with diagnosed BCRL, providing an analysis of both the volume and the distribution of the different tissue components.

MATERIALS AND METHODS

The entire arm was imaged with a fluid-sensitive STIR and a 2-point 3-dimensional T1W gradient-echo-based Dixon sequences, acquired in sagittal orientation and covering the same imaging volume. An automated image postprocessing procedure was developed to simultaneously (1) contour the external volume of the arm and the muscle fascia, allowing separation of the epifacial and subfascial volumes; and to (2) separate the voxels belonging to the muscle, fat, and fluid components. The total, subfascial, epifascial, muscle (subfascial), fluid (epifascial), and fat (epifascial) volumes were measured in 13 patients with unilateral BCRL. Affected versus unaffected volumes were compared using a 2-tailed paired t test; a value of P < 0.05 was considered to be significant. Pearson correlation was used to investigate the linear relationship between fat and fluid excess volumes. The distribution of fluid, fat, and epifascial excess volumes (affected minus unaffected) along the arm was also evaluated using dedicated tissue composition maps.

RESULTS

Total arm, epifascial, epifascial fluid, and epifascial fat volumes were significantly different (P < 0.0005), with greater volume in the affected arms. The increase in epifascial volume (globally, 94% of the excess volume) constituted the bulk of the lymphoedematous swelling, with fat comprising the main component. The total fat excess volume summed over all patients was 2.1 times that of fluid. Furthermore, fat and fluid excess volumes were linearly correlated (Pearson r = 0.75), with the fat excess volume being greater than the fluid in 11 subjects. Differences in muscle compartment volume between affected and unaffected arms were not statistically significant, and contributed only 6% to the total excess volume. Considering the distribution of the different tissue excess volumes, fluid accumulated prevalently around the elbow, with substantial involvement of the upper arm in only 3 cases. Fat excess volume was generally greater in the upper arm; however, the relative increase in epifascial volume, which considers the total swelling relative to the original size of the arm, was in 9 cases maximal within the forearm.

CONCLUSIONS

Our measurements indicate that excess of fat within the epifascial layer was the main contributor to the swelling, even when a substantial accumulation of fluid was present. The proposed approach could be used to monitor how the internal components of BCRL evolve after presentation, to stratify patients for treatment, and to objectively assess treatment response. This methodology provides quantitative metrics not currently available during the standard clinical assessment of BCRL and shows potential for implementation in clinical practice.