Long-term Efficacy of Allergen Immunotherapy

What Do We Expect?

Franco Frati; Ilaria Dell'Albani; Cristoforo Incorvaia

Disclosures

Immunotherapy. 2013;5(2):131-133. 

In This Article

Abstract and Introduction

Abstract

Evaluation of: Stelmach I, Sobocinska A, Majak P, Smejda C, Jerzynska J, Stelmach W. Comparison of the long-term efficacy of 3- and 5-year house dust mite allergen immunotherapy. Ann. Allergy Asthma Immunol. 109, 274–278 (2012). Allergen-specific immunotherapy (SIT) is the only treatment of allergic diseases able to maintain its efficacy after discontinuation of treatment. The available literature suggests that a 3-year duration of treatment maintains the efficacy on allergic symptoms for at least an equivalent period of time. The current paper compares the 3- and 5-year duration in children with dust mite-induced asthma, and confirms that 3 years of SIT maintains its effectiveness for a further 3 years after stopping, with no significant difference compared with 5 years. Thus, 3 years is likely to be an adequate duration of SIT; however, studies with more prolonged follow-up periods are needed to investigate the persistence of the clinical benefit over time.

Introduction

Allergen-specific immunotherapy (SIT) has proven efficacy in allergic rhinitis and asthma.[1] SIT modifies the immunological response to the administered allergen(s)[2] and this allows it to maintain its efficacy following treatment withdrawal.[3] However, the data on the long-term efficacy of SIT in respiratory allergy are not clear-cut. In 2007, Cox and Cohn reviewed the available literature on subcutaneous immunotherapy (SCIT).[4] Eight studies were analyzed: four performed with grass pollen, one with birch pollen, one with ragweed pollen, one with cat and dog epithelia, and one with dust mites. In most studies, SCIT had a duration of 3 years and the time period of assessment ranged from 3 to 12 years. Cox and Cohn used the relapse rate of respiratory allergy to establish the persistence of SCIT efficacy and found contrasting outcomes ranging from 0% 3 years after stopping in one study with grass pollen to 45% 3 years after stopping in the study with dust mites.[4] The better outcome in subjects allergic to pollen with respect to those allergic to mites seems to suggest that the extent of exposure is critical in favoring resensitization once SIT is discontinued. This concept seems reinforced if one takes into account the different results obtained with venom immunotherapy (VIT) in subjects allergic to Hymenoptera stings. In fact, in such an allergy where the exposure to the responsible allergen is occasional, the long-term efficacy is very good, with an estimated incidence of systemic reaction to a sting of approximately 10%, even 10–15 years after stopping VIT.[5] In addition, the residual reactions reported thus far were rarely severe and never fatal.

Sublingual immunotherapy (SLIT) was also evaluated in terms of its long-term efficacy. In an open prospective study, 60 children with mite-induced asthma were assigned to a 4–5-year course of SLIT (35 subjects) or to symptomatic drug treatment (25 subjects), and followed up for another 5 years.[6] In the SLIT group, significant differences were found at the 10-year time point versus baseline concerning the presence of asthma and the use of asthma medications, whereas no difference was observed in the control group. In a randomized placebo-controlled trial performed with the grass pollen preparation in tablet form in patients with rhinoconjunctivitis caused by grass pollen, 2 years after the discontinuation of a 3-year treatment, the mean rhinoconjunctivitis daily symptom score was significantly reduced (p < 0.004) in the actively treated group compared with the placebo group.[7] In addition, the percentage of days with severe symptoms during the peak grass pollen exposure was (including the post-treatment period) lower in the active than in the placebo group in all seasons, with relative differences of 49–63% (p < 0.0001).

It is apparent that there is a general agreement on 3 years as an adequate duration of SIT, while there is considerable heterogeneity regarding the time interval to extend the follow-up after stopping, as well as on the criteria to assess the respiratory disease activity.

Comments

3090D553-9492-4563-8681-AD288FA52ACE

processing....