A Novel Quantitative Computed Tomographic Analysis Suggests How Sirolimus Stabilizes Progressive Air Trapping in Lymphangioleiomyomatosis

Clinical Trial Validation of Automated Segmentation and Scoring of Pulmonary Cysts in Thoracic CT Scans

In cystic lung diseases such as lymphangioleiomyomatosis (LAM), a CT-based cyst score that measures the percentage of the lung volume occupied by cysts is a common index of the cyst burden in the lungs. Although the current semi-automatic measurement of the cyst score is well established, it is susceptible to human operator variabilities. We recently developed a fully automatic method incorporating adaptive features in place of manual adjustments. In this clinical study, the automatic method is validated against the standard method in several aspects. These include the agreement between the cyst scores of the two methods, the agreement of each method with independent tests of pulmonary function, and the temporal consistency of the measurements in the consecutive visits of the same patients. We found that the automatic method agreed with the standard method as well as the agreement between two trained operators running the same standard method; both methods obtained the same level of correlation with laboratory pulmonary function tests; the automated method had better temporal consistency than the standard method (p < 0.0001). The study indicates that the automatic method could replace the standard method and provide better consistency in assessing the extent of cystic changes in the lungs of patients.

Automated Segmentation and Measurements of Pulmonary Cysts in Lymphangioleiomyomatosis across Multiple CT Scanner Platforms over a Period of Two Decades

(1) Background: Lymphangioleiomyomatosis is a genetic disease that affects mostly women of childbearing age. In the lungs, it manifests as the progressive formation of air-filled cysts and is associated with a decline in lung function. With a median survival of 29 years after the onset of symptoms, computed-tomographic monitoring of cystic changes in the lungs is a key part of the management of the disease. However, the current standard method to measure cyst burdens from CT is semi-automatic and requires manual adjustments from trained operators to obtain consistent results due to variabilities in CT technology and imaging conditions over the long course of the disease. This can be impractical for longitudinal studies involving large numbers of scans and is susceptible to subjective biases. (2) Methods: We developed an automated method of pulmonary cyst segmentation for chest CT images incorporating novel graphics processing algorithms. We assessed its performance against the gold-standard semi-automated method performed by experienced operators who were blinded to the results of the automated method. (3) Results: the automated method had the same consistency over time as the gold-standard method, but its cyst scores were more strongly correlated with concurrent pulmonary function results from the physiology laboratory than those of the gold-standard method. (4) Conclusions: The automated cyst segmentation is a competent replacement for the gold-standard semi-automated process. It is a solution for saving time and labor in clinical studies of lymphangioleiomyomatosis that may involve large numbers of chest CT scans from diverse scanner platforms and protocols.

Unexpected sirolimus-stimulated airway hyperreactivity in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a multisystem disease affecting primarily women, characterised in the lung by proliferation of LAM cells, abnormal smooth muscle-like cells with dysfunctional tuberous sclerosis complex genes. This dysfunction results in activation of mechanistic target of rapamycin (mTOR), leading to LAM cell proliferation. Sirolimus (rapamycin) is the only United States Food and Drug Administration-approved treatment for pulmonary LAM, resulting in decreased LAM cell growth/size and stabilised lung function [1].

Computer grading of lung disease severity in patients with lymphangioleiomyomatosis referred for transplantation

Objectives

Lymphangioleiomyomatosis (LAM) patients with severe lung disease may be considered for lung transplantation. Clinical, physiologic, and quality of life data are usually employed for referral. The aim of this study was to determine whether computed tomographic measurement of lung volume occupied by cysts (cyst score) complemented clinical and physiologic data in supporting referral for transplantation.

Methods

Forty-one patients were studied. Pre-referral clinical data, pulmonary function tests, exercise testing, and high-resolution computed tomography (HRCT) scans were obtained. From HRCT, a computer-aided diagnostic program was employed to calculate cyst scores. These data were compared to those of 41 age-matched LAM patients not referred for lung transplantation.

Results

Cyst score, and % predicted FEV1 and DLCO were respectively, 48.1 ± 9.4%, 36.5 ± 9.1%, and 35.0 ± 10.7%. For the control group, cyst score, FEV1, and DLCO were respectively, 14.8 ± 8.3%, 77.2 ± 20.3%, and 66.7 ± 19.3%. Cyst score values showed a normal distribution. However, the frequency distribution of FEV1 was skewed to the right while the distribution of DLCO was bimodal. Correlations between cyst score and FEV1 and DLCO for the study group were respectively, r = − 0.319 and r = − 0.421.

Conclusions

LAM patients referred for lung transplantation had nearly 50% of lungs occupied by cysts. Correlations between cyst score and FEV1 or DLCO were weak; as shown previously, DLCO was better related to cyst number while FEV1 had a better association with cyst size. Given its normal distribution, cyst score measurements may assist in evaluation of pre-transplant severity of lung disease before referral for transplantation.

Assessment of Lung Structure and Regional Function Using 0.55 T MRI in Patients With Lymphangioleiomyomatosis

OBJECTIVES

Contemporary lower-field magnetic resonance imaging (MRI) may offer advantages for lung imaging by virtue of the improved field homogeneity. The aim of this study was to evaluate the utility of lower-field MRI for combined morphologic imaging and regional lung function assessment. We evaluate low-field MRI in patients with lymphangioleiomyomatosis (LAM), a rare lung disease associated with parenchymal cysts and respiratory failure.

MATERIALS AND METHODS

We performed lung imaging on a prototype low-field (0.55 T) MRI system in 65 patients with LAM. T2-weighted imaging was used for assessment of lung morphology and to derive cyst scores, the percent of lung parenchyma occupied by cysts. Regional lung function was assessed using oxygen-enhanced MRI with breath-held ultrashort echo time imaging and inhaled 100% oxygen as a T1-shortening MR contrast agent. Measurements of percent signal enhancement from oxygen inhalation and percentage of lung with low oxygen enhancement, indicating functional deficits, were correlated with global pulmonary function test measurements taken within 2 days.

RESULTS

We were able to image cystic abnormalities using T2-weighted MRI in this patient population and calculate cyst score with strong correlation to computed tomography measurements (R = 0.86, P < 0.0001). Oxygen-enhancement maps demonstrated regional deficits in lung function of patients with LAM. Heterogeneity of oxygen enhancement between cysts was observed within individual patients. The percent low-enhancement regions showed modest, but significant, correlation with FEV1 (R = -0.37, P = 0.007), FEV1/FVC (R = -0.33, P = 0.02), and cyst score (R = 0.40, P = 0.02). The measured arterial blood ΔT1 between normoxia and hyperoxia, used as a surrogate for dissolved oxygen in blood, correlated with DLCO (R = -0.28, P = 0.03).

CONCLUSIONS

Using high-performance 0.55 T MRI, we were able to perform simultaneous imaging of pulmonary structure and regional function in patients with LAM.

Ultra-Small Lung Cysts Impair Diffusion Without Obstructing Air Flow in Lymphangioleiomyomatosis

Background

Lymphangioleiomyomatosis (LAM) is a rare lung disease found primarily in women of childbearing age, characterized by the formation of air-filled cysts, which may be associated with reductions in lung function. An experimental, regional ultra-high resolution CT scan identified an additional volume of cysts relative to standard chest CT imaging, which consisted primarily of ultra-small cysts.

Research Question

What is the impact of these ultra-small cysts on the pulmonary function of patients with LAM?

Study Design and Methods

A group of 103 patients with LAM received pulmonary function tests and a CT examination in the same visit. Cyst score, the percentage lung volume occupied by cysts, was measured by using commercial software approved by the US Food and Drug Administration. The association between cyst scores and pulmonary function tests of diffusing capacity of the lungs for carbon monoxide (Dlco) (% predicted), FEV₁ (% predicted), and FEV₁/FVC (% predicted) was assessed with statistical analysis adjusted for demographic variables. The distributions of average cyst size and ultra-small cyst fraction among the patients were evaluated.

Results

The additional cyst volume identified by the experimental, higher resolution scan consisted of cysts of 2.2 ± 0.8 mm diameter on average and are thus labeled the “ultra-small cyst fraction.” It accounted for 27.9 ± 19.0% of the total cyst volume among the patients. The resulting adjusted, whole-lung cyst scores better explained the variance of Dlco (P < .001 adjusted for multiple comparisons) but not FEV₁ and FEV₁/FVC (P = 1.00). The ultra-small cyst fraction contributed to the reduction in Dlco (P < .001) but not to FEV₁ and FEV₁/FVC (P = .760 and .575, respectively). The ultra-small cyst fraction and average cyst size were correlated with cyst burden, FEV₁, and FEV₁/FVC but less with Dlco.

Interpretation

The ultra-small cysts primarily contributed to the reduction in Dlco, with minimal effects on FEV₁ and FEV₁/FVC. Patients with lower cyst burden and better FEV₁ and FEV₁/FVC tended to have smaller average cyst size and higher ultra-small cyst fraction.

Clinical Trial Registration

ClinicalTrials.gov; No.: NCT00001465; URL: www.clinicaltrials.gov

Cyst Ventilation Heterogeneity and Alveolar Airspace Dilation as Early Disease Markers in Lymphangioleiomyomatosis

Rationale: Lymphangioleiomyomatosis (LAM) is a rare disease associated with cystic destruction of the pulmonary parenchyma and chronic respiratory failure, and there are trials underway to determine if early intervention can prevent disease progression. An imaging technique that is sensitive to early regional disease would therefore be valuable for patient care and clinical trials.Objectives: We postulated that hyperpolarized ¹²⁹Xe MRI would be sensitive to ventilation abnormalities and alveolar airspace dilation in patients with mild LAM disease and normal pulmonary function and that ¹²⁹Xe MRI would reveal important features of cyst ventilation.Methods: ¹²⁹Xe ventilation and diffusion-weighted MR images were acquired in 22 patients with LAM during two breath-holds of hyperpolarized ¹²⁹Xe. ¹²⁹Xe ventilation defect percentage (VDP; percentage of voxels <60% of the mean whole-lung ¹²⁹Xe MRI signal) and apparent diffusion coefficient (ADC), a measure of alveolar airspace size, were quantified and compared with pulmonary function test parameters with Spearman statistics. Sixteen patients with LAM had a recent, clinical chest computed tomography (CT) scan available, and cyst ventilation was assessed by thresholding cysts on the CT images and registration to the ¹²⁹Xe ventilation images.Results: Ventilation deficits were observed in all patients with LAM, including those with normal pulmonary function and few cysts, and the mean VDP was 19.2% (95% confidence interval [CI], 14.8-23.5%). ¹²⁹Xe VDP was strongly correlated with forced expiratory volume in 1 second (FEV₁)/forced vital capacity (FVC) ratio (r = -0.51, P = 0.02) and diffusing capacity of the lung for carbon monoxide (Dl_CO) (r = -0.60, P = 0.009) but not with FEV₁ (r = -0.33, P = 0.13), likely because of the sensitivity of ¹²⁹Xe MRI to mild LAM disease in patients with normal FEV₁. The mean ADC was 0.048 cm²/s (95% CI, 0.042-0.053 cm²/s). In many cases, ADC was elevated relative to previously reported values in adults, and ADC was correlated with FEV₁, FEV₁/FVC ratio, and Dl_CO (P ≤ 0.02 for all). Co-registered ¹²⁹Xe MRI and CT imaging revealed considerable ventilation heterogeneity within individual patients with LAM and across patients with similarly sized cysts.Conclusions: ¹²⁹Xe MRI provides a means to assess the complex regional ventilation and alveolar airspace size changes of LAM with high sensitivity and may be a clinically useful future tool for screening, managing patients, and measuring treatment efficacy.

Lung function in Birt-Hogg-Dubé syndrome: a retrospective analysis of 96 patients

Background

Birt-Hogg-Dubé syndrome (BHD) is a rare autosomal dominant disorder caused by mutations in the FLCN gene coding for folliculin. Its clinical expression includes cutaneous fibrofolliculomas, renal tumors, multiple pulmonary cysts, and recurrent spontaneous pneumothoraces. Data on lung function in BHD are scarce and it is not known whether lung function declines over time. We retrospectively assessed lung function at baseline and during follow-up in 96 patients with BHD.

Results

Ninety-five percent of BHD patients had multiple pulmonary cysts on computed tomography and 59% had experienced at least one pneumothorax. Mean values of forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), FEV₁/FVC ratio, and total lung capacity were normal at baseline. Mean (standard deviation) residual volume (RV) was moderately increased to 116 (36) %pred at baseline, and RV was elevated > 120%pred in 41% of cases. Mean (standard deviation) carbon monoxide transfer factor (DLco) was moderately decreased to 85 (18) %pred at baseline, and DLco was decreased < 80%pred in 33% of cases. When adjusted for age, gender, smoking and history of pleurodesis, lung function parameters did not significantly decline over a follow-up period of 6 years.

Conclusions

Cystic lung disease in BHD does not affect respiratory function at baseline except for slightly increased RV and reduced DLco. No significant deterioration of lung function occurs in BHD over a follow-up period of 6 years.

Quantitative analysis of computed tomography of the lungs in patients with lymphangioleiomyomatosis treated with sirolimus

Objectives

We aimed to study sirolimus-related lung parenchymal changes by quantitative analysis of computed tomography (CT) of the lungs in patients with lymphangioleiomyomatosis (LAM).

Methods

We studied 20 participants from the Multicenter Lymphangioleiomyomatosis Sirolimus Trial for Safety study, who had undergone both thin-section CT scans and pulmonary function tests at baseline, 12, and 24 months. Quantitative CT parameters such as CT-derived total lung capacity, percentage of low attenuation area (LAA%), lung density histogram, fractal property of low attenuation area, and airway dimensions were analyzed, and correlations were conducted between the longitudinal change in each quantitative CT measurement and changes in pulmonary function were examined. Among 20 participants, pre-trial (n = 8) and post-trial (n = 16) CT data were also analyzed to deduce pathophysiologic implications of the serial changes in CT parameters during trial periods.

Results

FEV₁ significantly increased from baseline to 24 months (slope 3.71 ± 1.50 ml/month) whereas FVC didn't during sirolimus therapy. Strikingly, LAA%, and skewness and kurtosis of density histogram significantly increased from baseline to 24 months, while mean and mode CT values significantly decreased from baseline to 24 months. Statistically significant positive correlations were found between ΔFEV₁ and Δskewness (r = 0.465, p = 0.045). Taking the changes in lung density during pre-trial period into consideration, sirolimus decreases the area of -800 to -750 Housefield unit (HU) density and inhibits the decrease of -950 to -800 HU area during treatment, then producing the increased LAA% during the trial and post-trial periods. Given few sirolimus-related changes in airway dimensions, possible changes in lung mechanics may have contributed to increased FEV₁.

Conclusion

Our study suggests that the lung density histogram parameters, kurtosis, and skewness, may be useful as indicators of the efficacy of sirolimus.

Quantitative CT Analysis of Diffuse Lung Disease

Quantitative analysis of thin-section CT of the chest has a growing role in the clinical evaluation and management of diffuse lung diseases. This heterogeneous group includes diseases with markedly different prognoses and treatment options. Quantitative tools can assist in both accurate diagnosis and longitudinal management by improving characterization and quantification of disease and increasing the reproducibility of disease severity assessment. Furthermore, a quantitative index of disease severity may serve as a useful tool or surrogate endpoint in evaluating treatment efficacy. The authors explore the role of quantitative imaging tools in the evaluation and management of diffuse lung diseases. Lung parenchymal features can be classified with threshold, histogram, morphologic, and texture-analysis-based methods. Quantitative CT analysis has been applied in obstructive, infiltrative, and restrictive pulmonary diseases including emphysema, cystic fibrosis, asthma, idiopathic pulmonary fibrosis, hypersensitivity pneumonitis, connective tissue-related interstitial lung disease, and combined pulmonary fibrosis and emphysema. Some challenges limiting the development and practical application of current quantitative analysis tools include the quality of training data, lack of standard criteria to validate the accuracy of the results, and lack of real-world assessments of the impact on outcomes. Artifacts such as patient motion or metallic beam hardening, variation in inspiratory effort, differences in image acquisition and reconstruction techniques, or inaccurate preprocessing steps such as segmentation of anatomic structures may lead to inaccurate classification. Despite these challenges, as new techniques emerge, quantitative analysis is developing into a viable tool to supplement the traditional visual assessment of diffuse lung diseases and to provide decision support regarding diagnosis, prognosis, and longitudinal evaluation of disease. ^©RSNA, 2019.

Use of topical rapamycin in the treatment of superficial lymphatic malformations

BACKGROUND

The superficial lymphatic component of vascular malformations poses a significant treatment challenge. It is responsible for the majority of symptoms presented, and to date, there is no consensus regarding treatment.

OBJECTIVE

To evaluate the effectiveness of topical rapamycin in treating superficial lymphatic malformations (LM).

METHODS

A case series study was performed of patients with superficial LM, treated with topical rapamycin. The clinical characteristics of patients and the concentration and application mode of the drug were recorded. The changes in the signs and symptoms observed and associated adverse effects were noted and analyzed.

RESULTS

The study population consisted of 11 patients of an average age of 10.5 years. All were treated with topical rapamycin: 6 patients with a 1% concentration, 1 with a 0.8% concentration, and 4 with a 0.4% concentration. Changes in the clinical appearance of the lesions were observed in all patients. The associated symptoms, present in 9 of 11 patients, improved in every case. The mean follow-up time was 16.1 months.

LIMITATIONS

This study is retrospective, with a small sample size and considerable heterogeneity of lesions and treatment approaches.

CONCLUSION

Treatment with topical rapamycin modifies the clinical appearance and alleviates symptoms of superficial LM.

Use of CT Imaging to Quantify Progression and Response to Treatment in Lymphangioleiomyomatosis

BACKGROUND

In lymphangioleiomyomatosis (LAM), infiltration of the lungs with smooth muscle-like LAM cells results in cystic destruction and decline in lung function, effects stabilized by sirolimus therapy. LAM lung disease is followed, in part, by high-resolution CT scans. To obtain further information from these scans, we quantified changes in lung parenchyma by analyzing image "texture."

METHODS

Twenty-six texture properties were quantified by analyzing the distribution and intensity of pixels with a computer-aided system. Both cross-sectional and longitudinal studies were performed to examine the relationships between texture properties, cyst score (percentage of lung occupied by cysts), FEV₁, and diffusion capacity for carbon monoxide (Dlco), and to determine the effect of sirolimus treatment.

RESULTS

In the cross-sectional study, 18 texture properties showed significant positive correlations with cyst score. Cyst score and 13 of the 18 texture properties showed significant differences in rates of change after sirolimus treatment; 11 also significantly predicted FEV₁ and Dlco.

CONCLUSIONS

Increased cyst score was associated with increased texture degradation near cysts. Sirolimus treatment improved lung texture surrounding cysts and stabilized cyst score. Eleven texture properties were associated with FEV₁, Dlco, cyst score, and response to sirolimus. Texture analysis may be valuable in evaluating LAM severity and treatment response.

COPD assessment test as a possible tool for evaluating health-related quality of life in lymphangioleiomyomatosis

BACKGROUND

Lymphangioleiomyomatosis (LAM) is a progressive, cystic lung disease that causes an obstructive ventilatory impairment similar to chronic obstructive pulmonary disease (COPD) and impairs the health-related quality of life (HRQoL). Here, we extended the use of the COPD assessment test (CAT) to patients with chronic respiratory diseases other than COPD. Specifically, the CAT was administered to patients with LAM for the first time.

METHODS

Using data from 25 patients with LAM at Juntendo University who participated in the Multicenter Lymphangioleiomyomatosis Sirolimus Trial for Safety (MLSTS), we evaluated changes in pulmonary function, responses to HRQoL questionnaires (the CAT, St. George׳s Respiratory Questionnaire [SGRQ], EuroQOL Visual Analogue Scale [EuroQOL-VAS], and Functional Performance Inventory [FPI]), and the association between pulmonary function and HRQoL during a 24-month period of sirolimus treatment.

RESULTS

Forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), and CAT total scores improved over the 24 months of sirolimus treatment (5.33 ± 1.20 ml/month, 2.61 ± 1.16 ml/month, and -0.127 ± 0.022 score/month, respectively), whereas SGRQ total score, EuroQOL-VAS score, and FPI score did not. Most pulmonary functions at baseline were associated with the CAT breathlessness score during the first year. Longitudinal changes in FEV₁, FEV_1%predicted, or FEV₁/FVC correlated significantly with the scores of CAT total, CAT breathlessness, and SGRQ activity. When analyzed by stepwise multivariate regression within a linear mixed-effects model, CAT breathlessness and confidence scores were significantly associated with a change in FEV₁ from the baseline value (P = 0.0011, and P = 0.0441).

CONCLUSION

Our results suggest that the CAT is a useful instrument for assessing HRQoL in sirolimus-treated patients with LAM.

The efficacy and adverse events of mTOR inhibitors in lymphangioleiomyomatosis: systematic review and meta-analysis

Background

Lymphangioleiomyomatosis (LAM) is a rare lung disease and the mammalian target of the rapamycin (mTOR) inhibitors has been used as an effective therapy. Here we conducted a systematic review and meta-analysis with the aims to quantify the efficacy and safety of mTOR inhibitors in LAM patients.

Methods

The following databases were searched for clinical trials regarding LAM patients treated with mTOR inhibitors until December 2017: Pubmed, Embase, Cochrane Library and OVID medicine. Random effect models were used for the quantitative analysis.

Results

Nine eligible studies were included in our systematic review, 7 of which were used for the meta-analysis. In LAM patients, mTOR inhibitors improved forced expiratory volume in 1 s (FEV₁) and forced vital capacity (FVC) significantly, with the weighted mean difference (WMD) 0.15 L (95%CI: 0.08 to 0.22, P < 0.01, I² = 0%) and 0.22 L (95%: 0.11 to 0.32, P < 0.01, I² = 0%) respectively. There was no significant change in neither the diffusing capacity for carbon monoxide (WMD: 0.51 ml/mm Hg/min, 95%CI: -0.48 to 1.49, P = 0.31, I² = 0%) nor 6-min walking distance (WMD: 5.29 m, 95%CI: -18.01 to 28.59, P = 0.66, I² = 1%). The weighted partial response rate was 0.68 (95%CI: 0.53 to 0.84, P < 0.01, I² = 72%) for renal angiomylipoma. The cumulative incidence rates of common safety events were 50, 40, 23, 20 and 19% for oral mucositis, hyperlipidemia, headache, bone marrow suppression, and diarrhea, respectively. And most events were low grade and tolerant.

Conclusions

In LAM patients, there are improvements of FEV₁ and FVC after the application of mTOR inhibitors and over a half achieved the shrinkage of renal angiomyolipoma.

Trial registration

PROSPERO registration number: CRD42018085470. Registered 22 January 2018.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0874-7) contains supplementary material, which is available to authorized users.

Epidemiology of Rare Lung Diseases: The Challenges and Opportunities to Improve Research and Knowledge

Rare lung diseases encompass a broad spectrum of conditions and affect an estimated 1.2-2.5 million people in North America and 1.5-3 million people in Europe. While individual rare lung diseases affect less than 1 in 2000 individuals, collectively they have a significant impact upon the population at large. Hence it is vital to understand firstly the epidemiology and subsequently the pathogenesis and clinical course of these disorders. Through a greater understanding of these aspects of disease, progress can be made in reducing symptoms, containing healthcare costs and utilizing resources efficiently. Furthermore, a greater understanding of the pathobiology of rare lung diseases can inform both the pathogenesis and management of more common pulmonary disorders.In this chapter we review how epidemiological approaches and the utilization of patient registries has improved the knowledge and management of rare lung diseases. We further focus on the epidemiology of several of the more widely known rare pulmonary disorders, including idiopathic pulmonary fibrosis (IPF), cystic fibrosis (CF) and alpha-1 antitrypsin deficiency (AATD). To conclude we describe how patient advocacy groups and foundations have driven advances in research and management of ultra-rare lung diseases, namely, the major strides made in the management and understanding of lymphangioleiomyomatosis (LAM) and pulmonary alveolar proteinosis (PAP).We conclude that the models used to study some of the rarest of diseases may be successfully adopted by other rare and common disease communities, leading to improved care and the possibility of novel therapeutic options.

Emerging biomarkers of lymphangioleiomyomatosis

INTRODUCTION

Lymphangioleiomyomatosis (LAM) is a destructive lung disease affecting primarily women. LAM is caused by inactivating mutations in the tuberous sclerosis complex (TSC) genes, resulting in hyperactivation of mechanistic/mammalian target of rapamycin complex 1 (mTORC1). Over the past five years, there have been remarkable advances in the diagnosis and therapy of LAM, including the identification of vascular endothelial growth factor D (VEGF-D) as a diagnostic biomarker and the US Food and Drug Administration approval of sirolimus as therapy for LAM. In appropriate clinical situations VEGF-D testing can make lung biopsy unnecessary to diagnose LAM. However, there remains an urgent unmet need for additional biomarkers of disease activity and/or response to therapy. Areas covered: This work reviews VEGF-D, an established LAM biomarker, and discusses emerging biomarkers, including circulating LAM cells, imaging, lipid, and metabolite biomarkers, focusing on those with the highest potential impact for LAM patients. Expert commentary: Ongoing research priorities include the development of validated biomarkers to 1) noninvasively diagnose LAM in women whose VEGF-D levels are not diagnostic, 2) accurately predict the likelihood of disease progression and 3) quantitatively measure disease activity and LAM cell burden. These biomarkers would enable personalized, precision clinical care and fast-track clinical trial implementation, with high clinical impact.

Long-Term Effect of Sirolimus on Serum Vascular Endothelial Growth Factor D Levels in Patients With Lymphangioleiomyomatosis

BACKGROUND

Sirolimus reduces serum levels of vascular endothelial growth factor D (VEGF-D); the size of chylous effusions, lymphangioleiomyomas, and angiomyolipomas; and stabilizes lung function in patients with lymphangioleiomyomatosis (LAM).

METHODS

To determine whether reductions in VEGF-D levels are sustained over time, as well as parallel changes in lung function and lymphatic disease, we evaluated 25 patients with LAM and measured VEGF-D levels, lung function, and extent of lymphatic disease before and during sirolimus therapy.

RESULTS

Treatment with sirolimus stabilized FEV₁ and diffusion capacity for carbon monoxide (Dlco) over a period of 4.5 ± 1.6 years, caused resolution of lymphatic disease, and reduced the size of angiomyolipomas and VEGF-D levels (3,720 ± 3,020 pg/mL to 945 ± 591 pg/mL; P < .0001). Yearly changes in FEV₁ % predicted and Dlco % predicted were reduced from -7.4% ± 1.4% to -0.3% ± 0.5% (P < .001) and -6.4% ± 0.9% to -0.4% ± 0.5% (P < .001), respectively. Lower VEGF-D levels correlated with sirolimus therapy (P < .001), but no significant relationship was observed between reduction in VEGF-D levels and FEV₁ and Dlco during sirolimus therapy. The magnitude of VEGF-D decline was not related to the effect on lung function. Patients with lymphatic disease had higher serum VEGF-D levels, a greater reduction in VEGF-D levels, and better long-term sustained improvement in lung function during sirolimus therapy than did those without lymphatic disease.

CONCLUSIONS

Sirolimus therapy stabilizes lung function over many years of therapy while producing a sustained reduction in VEGF-D levels in patients with elevated levels preceding therapy. An association was not demonstrated between the magnitude of VEGF-D decline and the beneficial effect of sirolimus on lung function. Persistent improvement in lung function was observed in patients with lymphatic disease.