An efficacy comparison of anti-vascular growth factor agents and laser photocoagulation in diabetic macular edema: a network meta-analysis incorporating individual patient-level data

Diabetic macular edema (DME) is the leading cause of vision loss in patients with diabetic retinopathy [1]. Treatments include anti-vascular endothelial growth factor (VEGF) agents, laser, steroids, and surgery. Anti-VEGF agents are currently standard of care in DME treatment. These agents are known to target underlying abnormalities in the VEGF signalling cascade, which is a primary pathway in DME progression [2]. Anti-VEGF agents reduce the incidence of legal blindness, and their long-term efficacy and safety have been proven in numerous randomised trials [3‐8].

Direct randomised comparisons of anti-VEGF agents in DME, however, are limited to the Diabetic Retinopathy Clinical Research Network (DRCR.​net) Protocol T trial [4, 8], which only included ranibizumab at 0.3 mg (US dose) and did not include ranibizumab at 0.5 mg (EU dose) and is therefore not directly relevant to retina practice outside the United States. Many comparator DME trials have also used mean change in best-corrected visual acuity (BCVA; Early Treatment Diabetic Retinopathy Study [ETDRS] letters) after 12 months as a primary efficacy measure, but differences in baseline BCVA between trials, a likely treatment effect modifier [4, 8], may confound indirect comparisons.

Previous network meta-analyses (NMA) of anti-VEGF agents [9‐11] have attempted to adjust for baseline BCVA using aggregate data. These analyses provide useful data for decision-making, but meta-regression based on aggregate data may not mirror effects at the patient level and could also be confounded by non-linear covariable effects and other sources of heterogeneity between trials that are not accounted for by the variables included in the meta-regression [12, 13]. This bias is known as ecological bias.

The European Medicines Agency has recently issued a policy with a primary objective of making clinical reports and individual patient-level data (IPD) available to enable public scrutiny and allow for the application of new knowledge in future research [14]. Within-trial regression analysis based on IPD provides more robust adjustment for differences in BCVA between trials. However, to our knowledge, no published NMA has incorporated IPD.

The objective of this NMA was to perform an updated indirect comparison of the efficacy of approved anti-VEGF regimens and laser photocoagulation in DME based on mean change in BCVA and gain or loss of letters at 12 months. The NMA incorporated both aggregate data and IPD, where available. Different regimens, including fixed, as-needed (PRN), and treat-and-extend (T&E), were also included. These regimens have not been incorporated in detail in previous NMAs.

It is important for physicians and policymakers to compare the relative efficacy of DME treatments using the most robust methods available. Although direct head-to-head comparative trials provide stronger internal validity than indirect comparisons, there are a small number of these trials in DME (eg, DRCR.​net Protocol T) [4, 8], and there are no direct randomised comparative trial outcomes of IVT-AFL 2q8 and ranibizumab 0.5 mg (any regimen) available. The objective of this NMA was to perform an updated indirect comparison of IVT-AFL 2q8 versus relevant comparators, including ranibizumab 0.5 mg, from a previous publication [9]. Notably, this NMA incorporated IPD where available and adjusted for baseline BCVA, which is a known and important treatment effect modifier. To our knowledge, this is also the first NMA in DME that adjusted for any imbalance of treatment effect modifiers using IPD. Previous analyses that used only aggregate data are prone to ecological bias.

In the IPD and aggregate random-effects models, IVT-AFL 2q8 (after 5 monthly loading doses) showed strong evidence of superiority versus laser and ranibizumab 0.5 mg PRN with/without laser for mean change in BCVA from baseline and for gain of ≥15 ETDRS letters. IVT-AFL 2q8 also showed strong evidence of superiority for reducing ≥10 ETDRS letter losses versus ranibizumab 0.5 mg PRN with/without laser and versus ranibizumab 0.5 mg T&E. These results were consistent regardless of whether adjustment was made for baseline BCVA.

The BCVA results are similar to those in the previously published NMA that included fewer trials and did not include IPD [9]. In this previous NMA, there was an increase in mean BCVA at 12 months with IVT-AFL 2q8 over ranibizumab 0.5 mg PRN of 4.67 letters (95% CrI 1.85–7.52) in the random-effects Bayesian model (10 trials). However, there was no significant difference between IVT-AFL 2q8 versus ranibizumab 0.5 mg PRN for gain of ≥15 ETDRS letters (OR 1.87, 95% Crl 0.87–4.16) or loss of ≥10 ETDRS letters (OR 0.26, 95% Crl 0.05–1.31) in the random-effects Bayesian model (6 trials). The BCVA results are also consistent with those in a recent NMA that used an aggregate data approach [34]. This NMA of 21 trials (4307 eyes), which compared 11 different DME interventions including IVT-AFL and ranibizumab 0.5 mg, showed that IVT-AFL was the most favourable treatment at 12 months with respect to improvements in BCVA (OR 8.19, 95% CrI 5.07–11.96) and central macular thickness (OR -110.83, 95% CrI -190.25 to − 35.27) [34].

The availability and use of IPD can be important for ensuring that NMAs provide more robust adjustment for differences in between-trial baseline BCVA. In our NMA, we showed that adjustment for baseline BCVA did not affect the results in any model, but a lower BCVA at baseline was associated with a greater response to treatment. These findings are comparable with those observed in DRCR.​net Protocol T [4]. In DRCR.​net Protocol T, the mean change in visual acuity score (VAS) at 12 months was greater in patients with a lower BCVA score at baseline; for patients with baseline VAS of 74–78, the mean change in VAS was ~ 7 letters (IVT-AFL 2 mg) and ~ 6.5 letters (ranibizumab 0.3 mg) at 12 months, and for patients with baseline VAS of 24–53 letters the mean change in VAS was ~ 25 letters (IVT-AFL 2 mg) and ~ 17.5 letters (ranibizumab 0.3 mg) [4]. Similar findings were observed in a post hoc analysis of the VISTA-DME and VIVID-DME trials, IVT-AFL 2q8 treatment resulted in slightly better 12-month visual acuity outcomes in patients with baseline BCVA of ≥39 to ≤60 letters compared with those with a baseline BCVA of ≥61 to ≤73 letters; the mean change with IVT-AFL 2q8 at 12 months was 11.3 ETDRS letters (VIVID-DME) and 11.4 ETDRS letters (VISTA-DME) (baseline BCVA of ≥39 to ≤60 letters) and 8.6 ETDRS letters (VIVID-DME) and 9.5 ETDRS letters (VISTA-DME) (baseline BCVA of ≥61 to ≤73 letters) [35].

The comparison of IVT-AFL 2q8 versus ranibizumab 0.5 mg (PRN and T&E) also provides a useful complement to the direct comparative evidence of IVT-AFL 2 mg versus ranibizumab 0.3 mg from DRCR.​net Protocol T [4, 8]. The EURETINA guidelines question the extent to which the slower effect of ranibizumab seen in DRCR.​net Protocol T compared with IVT-AFL is attributable to the lower dose used [36]. This outcome is consistent with those in other published NMAs [9, 37]. In an updated Cochrane analysis of 24 trials (6007 patients with DME) [37], DME patients receiving ranibizumab (0.3 mg and 0.5 mg monthly) were less likely to gain ≥3 lines of visual acuity at 1 year compared with IVT-AFL (risk ratio [RR] 0.75, 95% CI 0.60–0.94). At 1 year, the visual acuity and CRT were worse with ranibizumab compared with IVT-AFL (mean difference in visual acuity: 0.08 logMAR, 95% CI 0.05–0.11; mean difference in CRT: 39 μm, 95% CI 2–76). It should be noted that ranibizumab 0.3 mg and 0.5 mg monthly were merged into 1 group as no heterogeneity was suspected between studies using these regimens in this Cochrane analysis. These authors concluded that the difference between IVT-AFL and ranibizumab was consistent with indirect evidence using ranibizumab 0.5 mg.

Despite the robust approach used in the current analysis, there are still some limitations associated with this updated NMA. We did not consider safety outcomes or longer-term efficacy outcomes, and there was limited availability of IPD in the public domain. Outcomes could also have been improved with the replacement of aggregate data from some trials (such as DRCR.​net Protocol T) with IPD; however, the availability of IPD from DRCR.​net Protocols I and J in addition to VIVID-DME, VISTA-DME, and VIVID-EAST enabled sufficient IPD to be included.

This NMA, which incorporated aggregate data and IPD to improve model robustness, consistently showed evidence of superiority of IVT-AFL 2q8 to laser and ranibizumab 0.5 mg PRN with/without laser for mean change in BCVA, gain of ≥15 ETDRS letters, and loss of ≥10 ETDRS letters at 12 months. IVT-AFL 2q8 was also superior to ranibizumab 0.5 mg T&E for loss of ≥10 ETDRS letters. These efficacy results were consistent irrespective of adjustment for baseline BCVA. Comparison of IVT-AFL 2q8 versus ranibizumab 0.5 mg PRN and T&E provides a useful complement to the direct comparative evidence of IVT-AFL 2 mg versus ranibizumab 0.3 mg given in DRCR.​net Protocol T. It is hoped that these data will be of additional benefit to those involved in the care of DME patients and to policymakers interested in developing future NMAs.