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Verteporfin photodynamic therapy for neovascular age-related ...

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30 Key changes to the protocolFor item 1, the primary outcome was the number of applications of VPDT in years 1 (≤ 350 days)and 2 (> 350 and ≤ 715 days). Treatment frequencies were cross-tabulated with TAP eligibilityand tested <strong>for</strong> significance using chi-squared statistics. We also compared treatment frequenciesin year 1 with treatment frequencies reported <strong>for</strong> the TAP trials. 30 For item 2, we calculated thetime until the first treatment episode was completed (see Classification of treatment as active orcompleted) or 350 days, whichever was later. These times were described as a Kaplan–Meier curve(see Figure 6), estimating the duration of follow-up when 50% of participants had completedtheir treatment.In order to make the comparison with the TAP trials, the cohort <strong>for</strong> this analysis was restricted topatients with a CNV lesion diagnosed as nAMD and who had completed their treatment or whohad completed follow-up <strong>for</strong> 1 or 2 years after the first treatment. The analysis was also limited toone eye per patient.B: Is ‘outcome’ the same in the NHS as in randomised trials?Objective B focused on patients who would have been EFT. We aimed to address this objective byestimating BCVA 1 year after the first treatment in patients classified as having completed theirtreatment <strong>for</strong> year 1. We fitted a mixed regression model to estimate the BCVA trajectory duringthe first year, using data up to 2 years where available. This method of analysis allowed all visitdata <strong>for</strong> an eligible eye to be included irrespective of adherence to the data collection schedule.The duration of follow-up (‘time’) was a covariate in the model; interactions of other covariateswith time represented non-parallel trajectories.A single model was used to answer objectives B and C and included the following covariates:<strong>age</strong>, gender, baseline BCVA, TAP eligibility, CNV composition, smoking status and whether ornot the fellow eye was the better-seeing eye. Coefficients from the model were used to estimateBCVA at 1 year <strong>for</strong> the EFT [objective (B)], IFT [objective (C)] and UNC subgroups. Inclusionof covariates was necessary because they were potential confounding factors when comparingoutcome across the EFT, IFT and UNC subgroups. The influence of the covariates in such a largecohort was also intrinsically of interest; inclusion of the UNC subgroup increased the precision ofthe analysis with respect to estimating the influence of the covariates.Because of substantial loss to follow-up in year 2, we again restricted our main analysis toestimating BCVA at 12 months <strong>for</strong> the cohort of patients described above <strong>for</strong> objective A (see A:Is verteporfin <strong>photodynamic</strong> <strong>therapy</strong> in the NHS provided as in randomised trials?).C: Is ‘outcome’ the same <strong>for</strong> patients ineligible from randomised trials?Objective C focused on patients who would have been IFT. A single model was used to addressobjectives B and C (see B: Is ‘outcome’ the same in the NHS as in randomised trials?).D: Is verteporfin <strong>photodynamic</strong> <strong>therapy</strong> safe when provided in the NHS?Adverse reactions and AEs were not classified as required <strong>for</strong> good clinical practice, althoughsuch events were promptly notified to the Data Man<strong>age</strong>ment Centre at the LSHTM in accordancewith good clinical practice. Attribution of ocular AEs to VPDT is difficult because such eventsmay occur as part of the natural history of nAMD. An AR was defined as an ocular or systemicreaction at the time of treatment which was recorded on the same day as the treatment with

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