Effects of treatments
The investigators collected plasma samples at baseline and then at 4 weeks and at 1 and 2 years before any ocular treatment was administered at the visits and the VEGF concentrations were measured. At 4 weeks, a total of 139, 130, and 141 samples were analyzed from patients who had been treated with aflibercept, bevacizumab, and ranibizumab, respectively, using a commercial immunoassay. The respective plasma VEGF concentrations at baseline were 28.50 pg/ml, 31.45 pg/ml, and 37.55 pg/ml.
“At the 4-week time point, there was virtually no change in the ranibizumab group (-0.02 pg/ml),” Dr. Jampol said. “However, in the aflibercept and bevacizumab groups, the respective decreases were -0.30 pg/ml and -0.31 pg/ml in the plasma VEGF levels.”
At the 1-year time point, 132, 115, and 130 samples of aflibercept, bevacizumab, and ranibizumab, were included. The investigators found little change in the free VEGF level in the ranibizumab group (-0.03 pg/ml).
In the aflibercept and bevacizumab groups, the plasma VEGF concentrations decreased (-0.10 pg/ml and -0.24 pg/ml, respectively). The difference between bevacizumab and ranibizumab reached significance (P < 0.001), which was also true at the 2-year time point, Dr. Jampol reported.
The investigators hypothesized about the timing of the injections. If the drug was cleared from the blood and the patient did not receive an injection for a certain period of time, the values might return to the normal level. “Indeed, that is what we found,” Dr. Jampol added.
With no injection administered within 1 month of the assay, at 1 year, the changes in the 3 VEGF levels were identical, Dr. Jampol pointed out. In eyes that had been treated within 1 month, the ranibizumab group had the smallest decrease and performed better than the other 2 drugs. In eyes that had had no injection in 2 months, the same results were found.