The effect of etidronate on choroidal neovascular activity in patients with pseudoxanthoma elasticum

Aim: To assess the effect of the
bisphosphonate etidronate on choroidal neovascular (CNV) activity in patients
with pseudoxanthoma elasticum (PXE).

Methods: This is an ancillary study in a
single center, randomized, double-blind placebo-controlled trial (RCT) in which
74 patients with PXE were assigned to either one-year etidronate or placebo
treatment. Spectral domain optical coherence tomography (SD-OCT) imaging and
color fundus photography were performed every three months for one year and
were systematically assessed on signs of CNV activity.

Results: In the etidronate group, 11
(30%) of the patients had CNV activity at baseline, compared to 25 (67%) of the
patients in the placebo group (P =
0.005). The proportion of eyes with CNV activity during the study ranged from
18–33% in the etidronate group and 42-56% in the placebo group and no
significant difference in improvement or worsening of CNV activity was found (P = 0.168). Using a generalized mixed model for repeated
measures, there was a protective effect of etidronate in crude analysis (RR
0.86, 95% CI 0.75 – 0.98) that disappeared when adjusting for baseline CNV
activity (RR 0.97, 95% CI 0.84 – 1.13).

Conclusion: In this post-hoc RCT analysis
we did not observe a protecting or deteriorating effect of etidronate on CNV
activity in patients with PXE after adjustment for baseline CNV.

研究目的：评估双膦酸盐依替膦酸（bisphosphonate etidronate）对弹性假黄瘤（pseudoxanthoma elasticum, PXE）患者脉络膜新生血管（choroidal neovascular, CNV）活性的影响。

研究方法：本研究为一项单中心、随机双盲安慰剂对照试验（randomized, double-blind placebo-controlled trial, RCT）的附属研究，共纳入74例PXE患者，随机分配至为期1年的依替膦酸治疗或安慰剂对照治疗。所有受试者在1年内每3个月接受一次光谱域光学相干断层扫描（spectral domain optical coherence tomography, SD-OCT）成像及彩色眼底摄影，并对脉络膜新生血管活性相关体征进行系统性评估。

研究结果：依替膦酸组基线时存在CNV活性的患者为11例（30%），安慰剂组为25例（67%），组间差异具有统计学意义（P=0.005）。研究期间，依替膦酸组出现CNV活性的患眼比例为18%~33%，安慰剂组为42%~56%；两组间脉络膜新生血管活性的改善或恶化情况均无显著差异（P=0.168）。采用广义混合重复测量模型进行分析，粗分析显示依替膦酸具有保护作用（相对风险RR=0.86，95%置信区间CI：0.75~0.98），但在校正基线CNV活性后，该保护作用消失（RR=0.97，95%CI：0.84~1.13）。

研究结论：本项事后RCT分析显示，在校正基线脉络膜新生血管活性后，未观察到依替膦酸对PXE患者的CNV活性存在保护或恶化作用。