Friday June 11 2010
AMD is a major source of visual impairment
A cancer drug “could save eyesight of tens of thousands”, says the Daily Mail. The newspaper reported on a trial that has assessed the drug bevacizumab (trade name Avastin) as a potential treatment for ‘wet’ age-related macular degeneration (AMD), a form of the progressive eye condition.
The research compared bevacizumab to existing treatments such as laser therapy and a drug called pegaptanib, which the researchers considered to be “standard care” NHS treatments. They found that, over the course of a year, bevacizumab both prevented further vision loss and improved vision compared with “standard care” options.
However, this study did not compare bevacizumab to a similar type of drug called ranibizumab (Lucentis), which has recently been approved as an AMD treatment by NICE. In order for bevacizumab to be approved for use within the NHS it must compare favourably to ranibizumab treatment as a method for improving vision in AMD. This was a small study and, although promising, further follow up is needed in a larger population to assess the benefits of bevacizumab for AMD.
Where did the story come from?
The study was carried out by researchers from Moorfields Eye Hospital and was funded by Trustees of Moorfields Eye Hospital and the Department of Health. It was published in the peer-reviewed British Medical Journal.
Newspapers have covered the scientific content of this research accurately, but tended to focus on whether bevacizumab is more cost-effective than ranibizumab, a NICE-approved treatment for AMD. However, this small study did not directly compare bevacizumab with ranibizumab, which was not yet approved when this trial began. The Daily Telegraph and the Daily Mail both highlighted that this comparison was not made by the study; however, a report by the BBC implied that this direct comparison had been made.
What kind of research was this?
This was a randomised controlled trial that looked at whether a drug called bevacizumab (also known as Avastin) improved an eye disease called age-related macular degeneration. Some patients experience a ‘wet’ form of the disease where new blood vessels grow in the eye, leading to loss of vision. In wet AMD blood vessels are induced to grow by a chemical called vascular endothelial growth factor-A (VEGF). Bevacizumab, which is already used in the treatment of some cancers, works by blocking the action of VEGF.
What did the research involve?
The study recruited 131 patients with wet AMD who were, on average, 81 years old. The study was carried out between August 2006 and November 2007. Half of the patients received a treatment of bevacizumab injected into the eye under a local anaesthetic. The patients received 1.25mg injections once every six weeks for eighteen weeks, followed by further injections at six-week intervals if required.
The “standard care” control group was designed to be representative of the types of care a patient might have received from the NHS at the time. This was either:
- photodynamic therapy: a laser treatment that seals leaking blood vessels when given following injections of a laser-activated drug called verteporfin
- injections of pegaptanib: a drug that stops blood vessel growth
- no active treatment: represented in this study by a placebo laser therapy only
In total, 16 patients received photodynamic therapy, 38 received pegaptanib and 12 received the placebo. Sixty-five patients received bevacizumab. Ranibizumab, a similar drug to bevacizumab, has recently been licensed for AMD, but at the time of the trial it had not yet received its licence. This meant the researchers could not compare the two drugs.
The patients had to be at least aged 50 and have similar degrees of visual impairment, with visual acuity scores ranging from 6/12 to approximately 6/96 (after correction with spectacles or the like). The patients had no structural damage to the fovea (the fine focus part of the retina) and were excluded if there was a history of cardiovascular events (heart attacks or unstable angina) or they had had a stroke in the preceding six months.
The researchers measured the proportion of patients that could see an extra 15 letters on an eye test at 54 weeks. This means that the patients could read three more lines on an eye test chart.
What were the basic results?
More than 90% of the patients continued to receive treatments up to week 48. The average number of bevacizumab injections that the patients received was seven out of a possible nine. In the control group, patients received 8.9 injections of pegaptanib or 3.2 photodynamic therapy treatments on average.
The results showed that:
- At 54 weeks 32% of patients receiving bevacizumab could read 15 extra letters on an eye test (95% confidence interval, CI 22% to 46%).
- In the control group only 3% of patients achieved this level of improvement (95% CI 0.4 % to 11%).
- The patients that received bevacizumab were less likely to have a decline in their vision over this time.
- In visual acuity tests, 9% of the bevacizumab group lost 15 letters or more, with 33% in the standard care control group experiencing such a decline.
Compared to performance at the start of the study, the visual acuity of patients treated with bevacizumab increased on average by 6.3 letters at week 6, by 6.6 letters at week 18 and by 7 letters at week 54. Patients receiving standard care had, on average, a loss of acuity at each six-week follow-up visit, with a mean loss of 9.4 letters by week 54.
The researchers did not find an overall difference in the side effects of each treatment.
How did the researchers interpret the results?
The researchers say that bevacizumab administered in six-weekly injections for AMD is superior in effectiveness to the standard care that was available at the start of the trial (verteporfin-assisted photodynamic therapy or pegaptanib). They say that bevacizumab has an acceptable side-effect profile and can be used to treat various subtypes of wet AMD.
This was a relatively small study, but it has shown promising results that bevacizumab may be an effective treatment for wet age-related macular degeneration compared with standard care. The researchers grouped various treatments, including placebo, as “standard care”, which they say is both a strength and a weakness of their study. They say that it is a strength because the group featured two active treatments that a patient would receive in the NHS (plus the sham treatment), but that this is also a weakness as it does not allow comparisons with a single treatment. Notably, including a placebo in the control group may have exaggerated the real difference between bevacizumab and other active treatments, since the placebo was likely to have had no effect on patients’ vision.
Although the researchers said that their control group was “standard care” for AMD, this study did not directly compare bevacizumab with ranibizumab, a similar type of drug that has since been approved by NICE as a treatment for AMD. In order for bevacizumab to be approved by NICE for use in the NHS it would have to compare favourably to ranibizumab.
Overall, this trial was too small to examine rare side effects of treatment, with the researchers themselves acknowledging that to do so would require a trial including thousands of patients. However, this study warrants further research in a larger population to assess further the potential benefits of using bevacizumab to treat AMD, including direct comparison with ranibizumab.