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HIV Treatment as Prevention. March 2010

March 4, 2010 Leave a comment

“Treatment as prevention” is in the news again as part of the media coverage of two conferences in California this month where claims were again made that treatment of virtually all HIV infected individuals could bring an end to the AIDS epidemic.

“Research shows that treatment could end the epidemic in thirty years” is typical of the headlines that enthusiastically announced this proposal to test and treat everybody found to be infected. Sadly, most of the reports I saw failed to comment on the huge practical difficulties that will need to be overcome to make such a project feasible. All ignored a probably insuperable ethical obstacle that will have to be confronted, which may well make the project completely unworkable. Added to these difficulties is the lack of agreement on the soundness of the mathematical model on which the proposal is based.

This initiative is also described as “treatment as prevention” although I also saw the term “seek, test and treat” used.

The prevention in “treatment as prevention” results from the reduced ability to transmit HIV that results from treatment with antiviral drugs.

It’s important to note that “treatment as prevention” can refer to two very different situations where infectivity is reduced by treatment. It describes the mathematical model, noted above that was published about a year ago in the Lancet, an influential weekly medical journal, which claims that the AIDS epidemic could be eliminated with regular tests for HIV and the immediate commencement of antiviral treatment of all who are infected. This is the title of the article: “Universal voluntary HIV testing with immediate antiretroviral therapy as a strategy for elimination of HIV transmission: a mathematical model “ (Reuben Granich and colleagues. Lancet 2009 373: 7).

Antiviral therapy according to this model would be given to all infected individuals whether or not the individual needs treatment. It would include lifelong treatment of healthier HIV infected people who have not been shown to benefit from it, such as those with more intact immune systems as well as those fortunate individuals whose disease does not progress. This is the root of the ethical problem; people who themselves are not known to benefit from treatment will be asked to receive it for a societal benefit. The benefits of treatment to such individuals are conjectural but as the drugs are not free from adverse effects, the risks are real. Unlike individuals with more advanced disease where the benefits of treatment vastly outweigh the risks, this cannot be known in the case of healthier HIV infected individuals.

This is very different to the analysis of the reduction in transmission of HIV that results from treating only those HIV infected individuals known to benefit from antiviral drugs. This is also referred to as “treatment as prevention” but unfortunately in none of the reports I saw was the distinction made between treatment only of those who benefit from it and treatment of all infected individuals. These two very different meanings of “treatment as prevention” were almost always conflated by commentators which could quite easily convey a mistaken impression that all HIV infected individuals are known to benefit from treatment.

Treatment must always be voluntary. But a voluntary decision to receive treatment does not mean a great deal if it is uninformed. The decision can most certainly seen to be coerced if misinformation is supplied. HIV infected individuals must be clearly informed about the risks and benefits of the intervention. As already noted, for individuals with more advanced disease, treatment without question provides a net benefit, but this is not known to be the case for HIV infected individuals with more intact immune systems.   There are suggestions that HIV infection may be associated with morbidity resulting from inflammatory reactions.   It is far from firmly established  if this is indeed the case and if it is, whether  it is an inevitable or even common  consequence of HIV infection, or if it can be prevented or treated with antiviral drugs.   It may also prove to be true that, as claimed by some investigators,  the newer antiviral drugs are less toxic than the older ones.  But the full range of their effects, particularly their longer term effects cannot be yet known. HIV disease can manifest in so many different ways that sorting out what is a drug effect from what is an effect of the infection itself may take a long time.

For healthier HIV infected individuals, the benefits of treatment remain conjectural as long as clinical trials have not been completed that are designed to provide a reliable answer to the question of when in the course of HIV disease it is best to start treatment. Quite remarkably, about fifteen years after potent antiviral drugs became available no such trial has been completed.

If a decision about whether or not to receive treatment is fully informed, healthier HIV infected individuals faced with an intervention that is accompanied with very real risks but only conjectural benefits may well choose to remain untreated, at least at that particular time in the course of their disease. The purpose of treatment is to reduce infectivity to others, but many might feel that this can be achieved with greater safety, and even possibly with greater reliability, by the use of condoms.  It should be said though that those researchers who point out the prevention benefits of treatment do not suggest that treatment is an alternative to condoms. On the contrary they recommend that treated individuals continue to use condoms.

Since the objective of treating all infected people is to end the epidemic, this can only be achieved if a large percentage of infected people receive treatment. But faced with a consent form clearly stating what is known about risks and benefits, it is most unlikely that enough healthier HIV infected people will agree to receive treatment. This is but one reason that if a decision to start treatment is properly informed the project is unlikely to enrol enough individuals to achieve its objective. A danger is that treatment of healthier HIV infected people may be claimed to have a net benefit with greater confidence than is warranted with information we presently have.   To succeed, the project also requires a lifetime of adherence to the treatment regimen.  When drugs are taken without confidence that they are of personal benefit, we cannot know how adherence to the regimen will play out.   Failures in this respect will not only diminish the chances that the project will succeed,  they can also result in the emergence of drug resistant strains of HIV which then could limit treatment options when treatment is needed.

There evidently is a belief that all HIV infected individuals, no matter the stage of disease will benefit from treatment. But this remains just that, a belief, as long as there is no firm evidence to support it. The evidence there is that healthier HIV infected individuals would receive a net benefit from treatment is of inferior quality, and therefore remains insecure. It comes from some retrospective observational studies. In such studies medical records are analyzed to compare outcomes in individuals who started treatment earlier with those who started later. Such studies however are beset with interpretative difficulties. Because individuals were not randomly assigned to start treatment early or later, a particular outcome, say improved survival of those starting treatment early, may result from whatever the reasons were that treatment was started at a particular time.

The great benefit of randomly assigning individuals to receive one treatment or another when two are compared is the elimination of interpretative  problems that arise when one or the other course of action is chosen.

The problem of such confounding factors was also discussed in a previous post: http://aidsperspective.net/blog/?p=75

The retrospective analysis most frequently cited in support of an earlier start to antiviral therapy, the NA-ACCORD study is also discussed in that post.

HIV infected individuals and those who advise them surely deserve more reliable evidence to support a decision whether to start or defer treatment than that provided by retrospective observational studies or worse, by mere belief.

Prospective randomized trials remain the best way to achieve this. They minimize bias, and thus misinterpretation, and remain the most reliable way to resolve uncertainty. There is no getting over this. Such trials may be expensive, and last a long time, but in the end, probably more time and money is lost by repeating inconclusive and conflicting retrospective studies. Surely we need to know, and not guess when it is best to start treatment.

START is a large clinical trial designed to provide an answer to the question of whether it is best to start treatment early or to defer it.     Another casualty of the pursuit of treatment as prevention that aims to treat all infected individuals is enrolment in START which may become more difficult. Those promoting treatment of all infected individuals as prevention must evidently feel that they already know the answer to be that an early start is best. How can this belief be reconciled with a respect for evidence based medicine that many of same experts claim to have?

We should rather concentrate our efforts on providing treatment to all HIV positive individuals who are at a stage in their disease where treatment is of unquestionable benefit. The fact that treatment reduces their infectivity to others is an added powerful argument to encourage widespread testing. An additional benefit is that people who know their HIV status are more likely to take steps to prevent infection of others.

The proposal to treat every infected person as a prevention strategy can be criticized on many levels. I have focussed here on the difficulty that arises from including the treatment of individuals not known to benefit from it. This can usefully be linked to support for and encouragement of enrolment in START.

The lack of concern for the ethical problem that arises from treating people not known to benefit from it is puzzling. A headline on the front page of the UK Independent newspaper reporting on the proposal to treat all infected people states: “AIDS: is the end in sight?”  The report quotes the opinion of one scientist that “the problem is that we are using the drugs to save lives, but we are not using them to stop transmission”   This statement  is quite remarkable.   The real problem arises when we administer drugs that can have adverse effects to people for any reason other than for their benefit.   We can only ask individuals to agree to take risks for a societal benefit if we have good reasons to believe that the endeavour has a good chance of success – in this case the grandiose one of ending the epidemic.  For reasons outlined above we cannot provide any confidence that this will be so.  At any rate many may feel that their societal concerns can be more safely met by using condoms, a proven way to reduce transmission of HIV.

I also wrote about this issue for the magazine POZ about a month ago. It can be seen by following this link. http://blogs.poz.com/joseph /archives/2010/02/treatment_of_hiv_dis.html

I also commented on this issue about a year ago. http://aidsperspective.net/blog/?p=152 This post repeats several points that were made then.