Lower esophageal sphincter injections for the treatment of gastroesophageal reflux disease.

Endoscopic therapies for the control of GERD offer the potential for significant symptomatic improvement while obviating many of the potential drawbacks associated with long-term medical therapy with acid suppressive or neutralizing medications and traditional antireflux surgery. Such endoluminal therapies are intended to be safe with a brief learning curve, easily administered in an outpatient setting without the need for general anesthesia, reproducible, and durable. LES injection therapies share the common theoretic method of action of bulking at the GEJ, leading to loss of sphincter compliance and distensibility. In the case of Enteryx, this sustained effect has been demonstrated to be secondary to chronic inflammation, fibrosis, and encapsulation resulting from a foreign body response to the injectate. Available data suggest that a majority of patients respond to LES injection therapies, as demonstrated by a decreasing usage of PPIs after implantation, the ability of many patients to terminate PPI use completely, and improved GERD-HRQOL scores. Responses seem reasonably durable in follow-up assessment up to 24 months post treatment. Although there may be some placebo effect associated with treatment, patients injected with Enteryx respond better than a control group of sham-treated subjects. Individuals treated with LES injections, however, represent a select subgroup of the overall population of refluxers. Study subjects, by and large, have had uncomplicated GERD with typical reflux symptoms of heartburn or regurgitation that have responded to PPIs. Patients who have severe anatomic derangements, such as esophageal strictures, persistent esophagitis, Barrett's esophagus, or sizeable hiatal hernias, are excluded from clinical trials, as are patients who have severe motility disorders or significant comorbid conditions. Similarly, patients who have responded poorly to PPIs and those who have primarily extraesophageal manifestations of GERD have not been studied. Outcomes to date have been assessed over the short to medium term; long-term outcome studies are lacking. The durability of response, therefore, remains largely unknown, as does the incidence of any long-term complications or side effects. A postmarket study to assess the long-term safety and durability of Enteryx therapy up to 36 months is under way, as required by the FDA, with a target enrollment of 300 patients. Detailed cost analyses have yet to be reported. Such data are important not only for comparing the various endoluminal therapies but also for comparison to standard medical therapy and antireflux surgery. At present, no randomized trials are completed that compare injection therapies to other accepted treatments of GERD. The ability to perform fundoplication safely and effectively after failed LES injection therapy is not well known, in that the number of subsequent surgical cases is small and the results largely anecdotal to date. Likewise, the ability to use LES injection as salvage therapy after failed fundoplication has not been tested. The data regarding endoluminal injection therapies are similar to those after endoscopic plication and radiofrequency application to the LES, in that a definite symptomatic response is observed, but the objective documentation of diminished esophageal acid exposure lags behind. Esophageal acid exposure is normalized in a minority of treated subjects and improved in an additional subgroup, whereas the rate of symptomatic response exceeds these objective improvements. The reasons for this disconnect are the subject of much speculation and controversy. A placebo effect has been discussed, but clearly more factors are at play. Perhaps a study effect also is important, in that patients enrolled in clinical trials for GERD control may be more likely to modify their dietary and lifestyle habits in an effort to bring about symptom relief. Maybe the understanding of the perception of reflux events is lacking, and these endoluminal therapies work mainly by altering the perception of reflux more than the amount of reflux itself. A recent technologic review of injection therapies for GERD concludes that the "data for Enteryx are as compelling as those of any other open-label evaluation of an endoluminal therapy for GERD". There is much to be learned about all endoluminal techniques. For now, LES injections are promising therapies lacking supportive evidence of long-term safety and efficacy. The available data justify their use only in patients who have GERD symptoms responsive to PPIs and who do not have significant comorbidities or complications associated with GERD. Whether or not the role of LES injection techniques will be expanded to include more complicated cases, patients who are partially responsive to PPIs, combination therapy with other endoluminal techniques, or salvage therapy after failed fundoplication awaits further study.