Surveying PRN strategy compliance

May 1, 2013

Strict monthly follow-up procedures should be implemented to ensure best results

Previous evaluations of ranibizumab treatment in a clinical setting by Dr Cohen and colleagues have demonstrated that the visual acuity of the patients with exudative agerelated macular degeneration (AMD) has only been stabilized rather than improved.2 These results did not coincide with randomized clinical trials and the Prospective Optical Coherence Tomography Imaging of Patients with Neovascular AMD Treated with intraOcular Ranibizumab (PrONTO) study.3 However, there was much less follow up and lower frequency of treatments in the study by Dr Cohen et al., which led them to believe that a long and regular follow up is required to achieve an improved visual acuity.

"In France, ophthalmologists frequently consider recommendations as suggestions that need to be evaluated in clinical practice," claimed Dr Cohen. "For example, decisions of re-treatment with anti-VEGF in neovascular AMD were, since 2007, taken based on the results of OCT more than on changes of visual acuity." In his opinion, this could be one of the reasons for poor compliance with recommendations, however, other factors, such as an excessive workload for surgeons, or an unwillingness from a patient to undergo such regular follow up examinations, could also contribute.

To examine the level of compliance with the recommended treatment regimen of ranibizumab, Dr Cohen and colleagues performed a restrospective, descriptive, observational study examining historical data on patients being treated with ranibizumab for subfoveal wet AMD. In total, data on 551 patients, who were followed by 16 ophthalmologists, were examined. The data included patient demographic, treatment regime and details of the disease as well as the preop visual acuity measurements and those taken at 3 months and 12 months post-op.

It was found that less than 40% of the patients were given the recommended ranibizumab treatment involving 3 monthly injections. "This was one of the most curious results," stated Dr Cohen, "because the initial treatment with 3 monthly intravitreal injections is the easiest part of the management of patients with neovascular AMD. We could not find any satisfactory explanation for this finding." Additionally, they found that more than half of the patients waited over a week after they had been diagnosed before treatment started.

The study demonstrated that when the recommended induction of intravitreal injections of ranibizumab was followed and treatment was commenced quickly after diagnosis, visual acuity gain was greater at 3 months follow up. However, no patients examined in this study were followed up as per the guidelines.

Dr Cohen stipulated that although he was not necessarily surprised by the results he was a little disappointed as he would have expected better visual acuity gains. "The results also suggest the use of different strategies, such as Inject and extend, in the management of patients," he added. "Additionally, because other studies report better results,4,5 modification of the PRN strategy may be considered, for example, capped PRN or reinforced PRN (i.e., with 2 or 3 consecutive injections in case of recurrence of the neovascular activity)."