| Photodynamic
therapy in the management of subfoveal choroidal neovascularisation secondary
to age-related macular degeneration.
Recent
studies now extending to two years have shown that the treatment known
as photodynamic therapy (PDT) is effective in reducing visual loss in the
short term in patients with predominantly classic subfoveal choroidal neovascularisation
(CNV) in AMD. The Royal College of Ophthalmologists has established a working
party consisting of experts in the field of macular degeneration and lay
advisors to examine the available evidence in order to provide guidance
to College members, the Department of Health and commissioners on the potential
use of PDT.
Treatment
according to the published TAP protocol requires 7 angiograms and an average
of 6 treatments within the first two years. Evidence exists that patients
with predominantly classic CNV of AMD will benefit from treatment in terms
of a reduction in the risk of losing 3 or more lines of vision over this
period.
Whilst
accepting that Visudyne is now licensed for use in the European Union,
the Working Party believes that there is insufficient evidence at present
to support the widespread use of photodynamic therapy in NHS or private
settings. Although the TAP study provides strong evidence that PDT with
verteporfin influences the visual outcome in the subgroup with predominantly
classic choroidal neovascularisation, a number of important questions remain
unanswered. These are:
-
The optimal
treatment regime: The experimental protocol required retreatment at study
visits if any leakage was seen in fluorescein angiogram regardless of location
or type of leakage and visual function status. It is unclear if treatment
is still necessary if a) residual leakage is located eccentric to the centre
of the fovea b) residual leakage is of the occult variety in any location
and c) if acuity is stable. Further evaluation is therefore needed to determine
the optimal treatment protocol.
-
Quality
of life: Whilst it is clear that there was a difference between the treatment
group and the placebo group, the extent of the effect and the value of
the benefit is still unclear as the quality of life studies were not undertaken
until much later in the TAP study.
-
Incidence
of early visual loss: There is evidence that a proportion of patients experience
transient visual loss with onset during the first week after therapy with
recovery by three to four weeks. Choroidal hypoperfusion is likely to be
the mechanism but the precise incidence and pathogenesis of this side effect
is unknown.
-
The number
of patients suitable for treatment: The proportion of patients with AMD
who have predominantly classic subfoveal CNV and therefore likely to benefit
from PDT with verteporfin is presently unknown. Consequently the number
of patients likely to be treated within the country each year is also unknown.
The Working
Party would wish to see a controlled introduction of PDT within the UK
Health Service whereby these questions can be answered systematically.
As the best outcome group consisted of patients with predominantly classic
CNV, any treating centre must have personnel with expertise in diagnosis
and reading of fluorescein angiograms to make these distinctions. To qualify
as a treating centre, the Working Party would recommend that the following
requirements are met.
a)
retinal specialisation
b)expertise
in stereo pair fluorescein angiography to permit accurate classification
of lesion components of CNV.
c)
experience of collecting data to agreed protocols through participation
in clinical trials
The
Working Party are currently developing protocols for case selection, investigation,
treatment, data collection and monitoring. The Working Party with the support
of the College intend to actively seek NHS R & D funding to move forward
with this process.
References
TAP
Study Group. Photodynamic Therapy of subfoveal choroidal neovascularisation
in age-related macular degeneration with verteporfin. One year results
of 2 randomized clinical trials. TAP report 1. Arch. Ophathmol., 1999;117:1329-45.
Brief
Summary
The Working
Party believes that there is insufficient evidence to support the widespread
use of PDT in the UK. The treatment effect is undoubted but small. As the
protocol stands it requires 7 angiograms and an average of 6 treatments
in the first two years and the cost may prove to be unacceptably high.
A number of important questions remain unanswered and to address these
the Working Party are currently developing protocols for case selection,
investigation, treatment, data collection and monitoring. The Working Party
with the support of the College intend actively to seek NHS R & D funding
to move forward with this process. |