Serum vascular endothelial growth factor-D levels in patients with lymphangioleiomyomatosis reflect lymphatic involvement

Abstract

Background: Lymphangioleiomyomatosis (LAM) is a rare multisystem disorder affecting primarily women of child-bearing age, and characterized by cystic lung destruction, tumors of the kidney (angiomyolipomas [AMLs]), and involvement of the axial lymphatics (lymphangioleiomyomas). Patients with LAM experience loss of pulmonary function attributed to the proliferation of abnormal-appearing smooth muscle-like cells (LAM cells). It is possible to group the LAM population by the presence or absence of extrapulmonary involvement (eg, AMLs, lymphangioleiomyomas, chylous effusions). Serum vascular endothelial growth factor (VEGF)-D, a lymphangiogenic factor, is higher in LAM patients than in healthy volunteers and has been proposed as a tool in the differential diagnosis of cystic lung disease. We assessed serum VEGF-D concentrations in relationship to clinical phenotype in LAM patients.

Methods: Serum VEGF-D levels were quantified by enzyme immunosorbent assay for 111 patients with LAM and 40 healthy volunteers. VEGF-D levels in patients with pulmonary LAM, with or without extrapulmonary manifestations, were compared to those of healthy volunteers.

Results: Serum VEGF-D levels were greater in patients with LAM compared to those of healthy volunteers (p < 0.001). However, when patient samples were grouped based on the extent of lymphatic extrapulmonary involvement (eg, lymphangioleiomyomas and adenopathy), the statistical difference was maintained only for patients with LAM with lymphatic involvement (p < 0.001), not for those patients whose disease was restricted to the lung. Serum VEGF-D levels are a good biomarker for lymphatic involvement (area under the curve [AUC], 0.845; p < 0.0001), and a fair predictor for LAM disease (AUC, 0.751; p < 0.0001). Serum levels correlated to CT scan grade (p = 0.033).

Conclusions: Serum VEGF-D concentration is a measure of lymphatic involvement in patients with LAM.

Figure 1

Serum levels of VEGF-D in LAM. Serum VEGF-D levels in all patients with sporadic LAM (n = 111) were compared to those of healthy volunteers (n = 40) [top, A]. Patient samples were further grouped and compared on the basis of thoracic or abdominal lymphatic involvement (presence (n = 77) or absence (n = 34) of lymphangioleiomyomas and/or adenopathy) [center, B] and the presence (n = 40) or absence (n = 71) of renal AMLs [bottom, C]. All groups were compared to healthy volunteers (n = 40). + = presence; − = absence; ♦ = serum measurement of VEGF-D from one patient or healthy volunteer; lines = mean values.

Figure 2

Correlation of VEGF-D serum levels or lymphatic involvement and disease severity in patients with LAM. Top, A: comparison of serum VEGF-D levels of patients with LAM between CT scan grade I and CT scan grade II and III (n = 111). The area outlined by the column represents the mean serum VEGF-D level of patients with LAM grouped by designated CT scan grade. Standard error bars. Bottom, B: comparison of the number of LAM patients, with (+) or without (−) lymphatic involvement, having CT scan grade I and CT grade II and III (n = 111). The area outlined by the column represents the number of patients with LAM grouped by designated CT scan grade and status of lymphatic involvement.

Figure 3

Association between serum VEGF-D levels in patients with LAM and initial Dlco percent predicted. Top, A: univariate analysis of correlation between the serum VEGF-D levels in 111 patients with LAM and the initial Dlco percent predicted. Center, B, and bottom, C: for multivariate analysis, LAM patients were grouped by lymphatic involvement. Serum VEGF-D levels correlated with initial Dlco percent predicted for patients with lymphatic involvement. (+) lymphatics = patients with lymphangioleimyomas and/or adenopathy; (-) lymphatics = patients without lymphangioleiomyomas or adenopathy; ♦ = serum measurement of VEGF-D from one patient with LAM.

Figure 4

Association of lymphatic involvement in patients with LAM and initial Dlco percent predicted. The presence of lymphatic involvement in patients with LAM is correlated to lower Dlco percent predicted (p = 0.002; n = 111). ♦ = one patient with LAM. See the legend of Figure 3 for explanation of symbols not used in the text.

Figure 5

Model representing the diagnostic ability of serum VEGF-D levels for predicting lymphatic involvement or LAM disease. A larger AUC indicates a higher measure of accuracy of the diagnostic test. Se, Sp, and predicted values are given at the optimal cutoff point where the Se and Sp are maximized (arrows) [n = 111]. Top left, A: ROC curve for detecting lymphatic involvement in a sample of LAM patients only. The AUC is 0.813 (p < 0.0001). The threshold VEGF-D value is 949 pg/mL. Top right, B: ROC curve for detecting lymphatic involvement in a combined sample of LAM patients and healthy volunteers. The AUC is 0.845 (p < 0.0001). The threshold VEGF-D value is 1,317 pg/mL. Bottom left, C: ROC curve for diagnosing LAM in a combined sample of LAM patients and healthy volunteers. The AUC is 0.751 (p < 0.0001). The threshold VEGF-D value is 1,239 pg/mL. Bottom right, D: ROC curve for diagnosing only pulmonary LAM in a combined sample of pulmonary LAM, extrapulmonary LAM, and healthy volunteers. The AUC is 0.66 (p = 0.046). The threshold VEGF-D value is 1,202 pg/mL.