Photodynamic therapy appears less effective in patients taking aspirin

Non-aspirin takers required fewer treatments and achieved better visual results, retrospective chart review indicated.

Patients taking aspirin while undergoing photodynamic therapy for choroidal neovascularization may require more treatments and have poorer vision results than those not taking aspirin, a study shows.

Robert A. Stoltz

“Aspirin is a platelet inhibitor, and perhaps by inhibiting the effect of platelets to cause localized thrombosis, we may be actually interfering with one of the main mechanisms of action of photodynamic therapy,” Robert A. Stoltz, MD, PhD, told Ocular Surgery News in a telephone interview.

Dr. Stoltz and colleagues conducted a retrospective chart review on 244 eyes of 222 patients who underwent PDT with Visudyne (verteporfin, Novartis/QLT) between 2001 and 2004 at the Scheie Eye Institute at the University of Pennsylvania.

“Particularly now, when we have other regimens such as anti-VEGF treatment and combination treatment — photodynamic therapy with anti-VEGF medication — it might be important to consider medications our patients are on to see whether or not what we’re doing for the eye might be influenced by the medications that these patients are taking for other systemic problems,” he said.

Dr. Stoltz said he believes that despite a decrease in its use in recent years, PDT still has a place in the treatment of CNV and suggested that less than satisfactory results seen in the past with PDT may have something to do with systemic medications such as aspirin.

Study design

All study patients presented at the age of 18 years or older for age-related macular degeneration, presumed ocular histoplasmosis or myopic degeneration, according to the study.

For comparison, subjects were split into two groups: 102 eyes of 92 subjects who took aspirin and 142 eyes of 130 subjects who did not take aspirin. The authors noted that aspirin takers were an average of 4 years older than non-aspirin takers and that more aspirin takers were men.

All patients were followed for at least 3 months after the final treatment session. Because of the influx of alternative treatments after 2004, patients receiving treatment after that year were excluded from the study.

More treatments

Aspirin takers underwent a range of one to 11 PDT treatments, with an average of 3.11 treatments. Non-aspirin takers underwent one to eight treatments and averaged 2.39 treatments. Aspirin takers requiring more than one PDT treatment received those treatments at an interval of 88 days, compared with 77 days for non-aspirin takers.

Additionally, aspirin takers were followed for an average of 3.5 months longer than non-aspirin takers because of the larger number of treatments required, according to the study.

“With regards to the increased number of treatments, I think that’s something that we need to keep in mind when recommending photodynamic therapy for our patients,” Dr. Stoltz said. Specifically, he suggested that PDT may be more effective in patients taking aspirin if they cease taking the medication for a week before and for 1 to 2 weeks after their PDT session.

“I think it is a great adjunctive medication for patients who have cardiovascular disease, and I don’t think that we should tell our patients not to be on it just because of their eye disease. However, I think that what we have to do is start taking it into consideration, as the underlying diseases for which patients are treated with aspirin may themselves influence the efficacy of PDT, and our study was not meant to make this distinction,” he said.

Vision outcomes

At final follow-up, non-aspirin takers achieved an average visual acuity of 1.1 logMAR, compared with 1.39 logMAR for aspirin takers (P = .003). Aspirin takers had an average loss of vision of 0.55 logMAR, compared with a loss of 0.24 logMAR for non-aspirin takers (P = .0003).

Additionally, aspirin takers were 2.6 times more likely to lose three or more lines of vision than non-aspirin takers; such a loss was seen in 58% of aspirin takers and 35% of non-aspirin takers (P = .0003).

“There was basically a slightly greater chance for vision loss in those patients taking aspirin, as opposed to those who were not taking aspirin,” Dr. Stoltz said. “This retrospective study is limited in the level of detail that can be obtained about medical comorbidities, and our results should be interpreted accordingly.”

For more information:

Robert A. Stoltz, MD, PhD, can be reached at Georgia Retina, P.C., 465 Winn Way, Suite 100, Decatur, GA 30060; 404-299-5209; e-mail: stoltz.robert@gmail.com. Dr. Stoltz has no direct financial interest in the products discussed in this article, nor is he a paid consultant for any companies mentioned.

Reference:

Ranchod TM, Guercio JR, et al. Effect of aspirin therapy on photodynamic therapy with verteporfin for choroidal neovascularization. Retina. 2008;28:711-716.

Jessica Loughery is an OSN Correspondent based in Philadelphia.