Comparaison Macugen et triamcinolone, en association avec PDT (VERITAS) : problème de puissance…

Il y a un an environ, une nouvelle publiée par Ophthalmology Times Europe (OTE) laissait entendre qu’il n’y avait « pas de différence entre Macugen et triamcinolone » (associés à la photothérapie dynamique) en traitement de la DMLA exsudative… et que l’essai qui comparait les deux associations avait été arrêté précocément (sans précision sur le motif de cet arrêt prématuré, dont on pouvait donc penser qu’il s’agissait justement de l’absence de différence entre les deux traitements…) :

No difference between Macugen and triamcinolone
14 June 2007 – Ophthalmology Times Europe

A study, which was halted before the completion of enrolment, failed to demonstrate any difference in the visual outcomes or safety concerns in patients with neovascularization secondary to age-related macular degeneration (AMD) who were treated with photodynamic therapy (PDT) in combination with either intravitreal injections of Macugen (pegaptanib sodium) or triamcinolone, according to a presentation at this year’s meeting of the Association for Research in Vision and Ophthalmology (ARVO) […]

Dans un article du 18 juin, OTE revient sur cet essai (« VERITAS ») : en fait, ce serait en raison des résultats des études du Lucentis qu’il aurait été arrêté, et non par manque d’efficacité du Macugen par rapport à la triamcinolone.
L’absence de différence significative entre les deux groupes peut alors tout simplement s’expliquer par le manque de puissance de l’étude (puisque seulement un tiers de l’effectif initialement prévu a été inclus)… ce d’autant que les groupes ne sont pas comparables au départ !

Outre qu’aucune conclusion ne peut être tirée de l’étude VERITAS, cet exemple rappelle également que les résultats d’essais doivent toujours être analysés avec précaution

Trial studies triamcinolone or pegaptanib in conjunction with PDT with verteporfin
18 June 2008 by Lynda Charters – Ophthalmology Times

[…] Speaking at the American Academy of Ophthalmology annual meeting, Peter K. Kaiser, MD, reported the 12-month results of the Verteporfin Intravitreal Triamcinolone Acetonide Study (VERITAS), which was carried out to evaluate the safety and efficacy of intravitreal triamcinolone acetonide (Kenalog, Bristol-Myers Squibb) or pegaptanib (Macugen, OSI/Eyetech/Pfizer) in combination with photodynamic therapy (PDT) with verteporfin (Visudyne, Novartis Pharmaceuticals).
[…]
The patients were randomly assigned 1:1:1 to standard fluence PDT and pegaptanib or 1 mg or 4 mg of triamcinolone.

A total of 111 patients were enrolled when the study was finished early; this number was less than the original 339 patients desired because of the results of the study of ranibizumab (Lucentis, Genentech), Dr. Kaiser explained. The number of patients reduced the power of the study from 80% to 43%, he added.
[…]
Dr. Kaiser also pointed out another limitation : the baseline characteristics were unbalanced. In the group that received pegaptanib, significantly worse VA was seen compared with the group treated with 1 mg of triamcinolone.
In addition, both groups treated with triamcinolone had a significantly greater number of patients with cataract.
The lesion types also were unbalanced among the treatment groups, with more classic CNV in the group treated with pegaptanib and more occult CNV without a classic component in the group treated with 4 mg of triamcinolone, Dr. Kaiser said.

Regarding the primary endpoint of loss of fewer than 15 letters of vision at the 12-month time point, no significant difference was seen among the treatment groups.
[…]
« Although the primary outcomes did not differ between PDT and pegaptanib and PDT and steroid, no definitive conclusions could be drawn about the study because of the low study power, » Dr. Kaiser said. « We can only say that treatment with standard fluence PDT is safe, and there were no cases of acute severe decreases in VA. »