(IVB) have been found to be effective for the treatment of retinopathy of prematurity (ROP). However, serum levels of vascular endothelial growth factor (VEGF) have been found to be suppressed for 2 weeks after IVB in patients with ROP. Changes in serum VEGF levels after IVB in patients with ROP may be important because VEGF also plays a role in the neurodevelopment of newborns. OBJECTIVE To investigate the correlation of levels of VEGF and related growth factors with bevacizumab levels in the systemic circulation after IVB in patients with type 1 ROP. DESIGN, SETTING, AND PARTICIPANTS We studied a prospective case series at an institutional referral center from December 1, 2011, through February 28, 2013. We enrolled patients with type 1 ROP who received IVB. We collected blood samples before and for as long as 8 weeks after IVB. The samples were tested for serum levels of bevacizumab and growth factors, including VEGF, VEGF receptor 1 (VEGFR1), VEGFR2, Tie2, erythropoietin, transforming growth factor β1, insulinlike growth factor type 1, angiopoietin 1, angiopoietin 2, angiopoietinlike 3, and angiopoietin 4. The serum concentrations of these factors were measured using enzyme-linked immunosorbent assays. MAIN OUTCOMES AND MEASURES Serum levels of VEGF, bevacizumab, and the other growth factors before and for as long as 8 weeks after IVB. RESULTS We enrolled 8 patients with type 1 ROP. Bevacizumab levels were elevated 1 day after IVB in the 3 patients for whom measurements were available (mean [SD], 1425 [1010 (95% CI, 0-3934)] ng/mL; P = .13) and remained detectable in the serum as long as 8 weeks after IVB (285 ng/mL for the 1 patient with a measurement available). Serum VEGF levels were suppressed for the same period (mean [SD] level at 1 day after IVB, 379 [226 (95% CI, 190-568)] pg/mL for the 3 patients with measurements available; at 8 weeks, 216 pg/mL for the 1 patient with a measurement available). We found a negative correlation between the serum levels of bevacizumab and VEGF in the patients with ROP who received IVB (r = −0.43 [95% CI, −0.67 to −0.10]; P = .01). No changes were identified in the serum levels of any of the other factors after IVB. Bevacizumab may interfere with the actual level of VEGF in the serum, and the total VEGF level in the serum cannot be determined when bevacizumab is present. Wide CIs were noted in the measurement of these factors, probably owing to the small number of patients enrolled in this study. CONCLUSIONS AND RELEVANCE Serum VEGF levels were suppressed for 2 months after IVB in patients with type 1 ROP owing to the leakage of bevacizumab into the systemic circulation.
