1. Introduction
Chronic Obstructive Pulmonary Disease (COPD) is a progressive respiratory disease characterized by airflow limitation and persistent respiratory symptoms[
1]. According to the most important consensus documents[
1], the management of stable COPD mainly consists of the use of inhaled medications which have been shown to relieve symptoms, reduce exacerbations and improve the quality of life[
2]. One of the leading treatment strategies is the concept of triple therapy, which combines an inhaled corticosteroid (ICS), a long-acting muscarinic antagonist (LAMA), and a long-acting beta-agonist (LABA). Triple therapy is currently indicated for maintenance treatment in patients experiencing frequent exacerbations and in patients with a significant symptomatic burden despite dual bronchodilator therapy [
1,
2]. Randomized clinical trials have shown that triple therapy can improve lung function, quality of life and reduce exacerbations compared to dual therapy [
3,
4,
5,
6].
Despite the widely accepted role of triple therapy, concerns have been raised about the safety of long-term ICS use, such as the potential risk of adverse events, particularly pneumonia. A systematic review and meta-analysis of three RCTs found a higher incidence of pneumonia in those who were randomized to triple therapy compared with the LABA/LAMA group (Risk ratio: 1.53; 95% confidence interval (CI) 1.25-1.87; I
2=19.7%) [
7]. Conversely, another meta-analysis by Calzetta et al. [
8] indicated that ICS discontinuation may result in an increased risk of severe exacerbations, impairment of lung function, and worsened quality of life, although the impact may not be clinically significant [
8].
The current indication for ICS withdrawal from triple therapy to LABA-LAMA is limited to COPD patients with no history of exacerbations in the past year, and the recommendation had only moderate certainty of evidence [
2]. Many authors question the rationale for changing a therapy that provides significant patient benefit: there is a considerable lack of evidence on the effects of de-escalating from triple therapy to LABA/LAMA, and the available data paint an unclear picture. One of the main issues leading to the tapering of ICS and the step-down to LABA/LAMA may be the need to balance the benefits of inhaled steroids against their potential risks, particularly pneumonia. Interestingly, evidence from “real-world” studies suggests that dual bronchodilator therapy is as effective as triple therapy for many patients, particularly those without a history of frequent exacerbations, but with a better safety profile [
9,
10].
In summary, given the conflicting evidence and the availability of different treatment combinations, the main goal of this systematic review and meta-analysis is to analyze the evidence from clinical trials that have investigated the efficacy and safety of the de-escalation strategy discontinuing ICS compared to the continuation of LABA/LAMA/ICS in subjects with COPD.
4. Discussion
In the current meta-analysis, we systematically evaluated the efficacy and safety of de-escalation with ICS withdrawal from ICS/LABA/LAMA to LABA/LAMA compared to continuation of triple therapy. The main findings of our meta-analysis are that no significant increase in moderate or severe exacerbations may be attributed to ICS withdrawal, whilst critical evidence emerges upon examining patients with different eosinophil thresholds. Specifically, those with ≥300 eosinophil/µL or greater than 2% experienced a significant increase in exacerbations and a greater decline in lung function when de-escalating from ICS/LABA/LAMA to LABA/LAMA, suggesting that ICS should be continued in this subgroup. Moreover, no significant differences were observed in our safety outcome analysis, including data on all-cause mortality and pneumonia risk.
We found only one meta-analysis similar to this one in a systematic review of the literature [
22]. Our paper extends the quantitative analysis by Koarai et al. [
22] and is, to our knowledge, the first comprehensive analysis attempting to summarize the existing evidence on the de-escalation strategy from ICS/LABA/LAMA to LABA/LAMA in the treatment of stable COPD, including a subgroup analysis according to the eosinophil count. While individual studies have previously investigated de-escalation therapy in COPD, a comprehensive synthesis of findings from randomized controlled trials and real-world studies was absent.
It should be emphasized that despite the importance of the clinical problem addressed in this meta-analysis and the very large number of patients potentially involved, our literature search found a limited number of studies and a significant methodological heterogeneity among them, encompassing variations in study design, patient populations and ICS withdrawal protocols. Patients' current smoking status is a significant factor in COPD prognosis and treatment response [
23]. However, across the included studies, data on this variable were highly heterogeneous. For instance, in the WISDOM trial [
15,
16], 66.6% of the total sample were current smokers, whereas in the DACCORD trial [
20] a small percentage had no smoking history. A notable degree of heterogeneity was evident in the duration of triple therapy prior to enrollment across the studies considered. Participants had been on triple therapy before baseline for at least three months in four studies [
17,
18,
19,
20], six weeks in the WISDOM trial [
15,
16]. In one “real-world” study [
21], patients were included irrespective of their time on triple therapy but reported a small percentage of participants that had generically been on ICS/LABA/LAMA for less than 12 months. In addition, the studies considered as "triple therapy" both when ICS, LABA and LAMA were administered in a single inhaler and in separate inhalers, nevertheless, this issue has been reported by several authors as a potential determinant of differential benefits for subjects [
24,
25].
As enlightened by our jackknife sensitivity analysis, such notable variance in pooled estimates was predominantly attributable to the inclusion of one study characterized by distinct methodological approaches. Regarding the analysis of the exacerbation rates, exclusion from the meta-analysis of the DACCORD trial [
20] yielded a substantial change in the pooled estimates. The DACCORD trial was a longitudinal, non-interventional “real-world” study conducted in three different cohorts [
20,
26]. Only cohort 3 met our inclusion criteria (received triple therapy for ≥ 6 months), and then each patient's physician decided to continue triple therapy or switch to a LABA/LAMA, so the data were included in this meta-analysis and discussed here. Briefly, patients de-escalated to LABA/LAMA had a lower incidence of both moderate and severe exacerbations compared with those in the ICS/LABA/LAMA group (HR: 0.58, 95% CI 0.42-0.79), improved in symptoms (absolute change from baseline in CAT score -2.0 for LABA/LAMA group and -1.0 for ICS/LABA/LAMA group, p=0.003) and had a lower incidence of adverse events. These results from the DACCORD trial [
20] differ significantly from the other available evidence and need to be interpreted with caution. First, the “non-interventional” design could significantly contribute to the observed results. Second, the observed differences may be due to the severity of COPD in the patient population treated with ICS/LABA/LAMA. In fact, the mean predicted percentage of FEV
1 (57.7%) was lower in the triple therapy group than in the LABA/LAMA group (66.9%), indicative of more severe disease at baseline. This severity is further highlighted by the higher frequency of exacerbations in the 12 months prior to study entry in the ICS/LABA/LAMA group (48.9%) than in the LABA/LAMA cohort (43.5%). Despite the methodological limitations of the non-interventional design, the DACCORD trial probably more closely reflects the “real-world” clinical management of patients with COPD on long-term triple therapy and demonstrates the clinical propensity of physicians to continue triple therapy for patients with unstable disease. This clinical decision-making is logically consistent with a cautious approach to managing patients who are more prone to exacerbations. Consequently, non-frequently exacerbating COPD patients were considered suitable candidates for ICS withdrawal and clinicians were dissuaded from de-escalating treatment in patients with a history of frequent exacerbations prioritizing disease control and prevention of further exacerbations. Of note, there is no mention of whether eosinophil counts had a role in de-escalating to LABA/LAMA or remaining on triple therapy.
Also in consideration of the extensive debate over the past years regarding the role of ICS in COPD [
27,
28,
29,
30,
31], the analysis of data elaborated in the present meta-analysis suggests several considerations of potential interest for clinicians.
1) the actual relevance of using trough FEV
1 as an outcome measure in COPD patients may be questionable. Data from different studies appear to be influenced by the methodology used and, most importantly, no variation reaches the 100 ml target, which is the well-recognized “minimal clinically important difference” (MCID) [
32,
33]. Therefore, although the assessment of this measure could be of relevance to demonstrate the therapeutic effect, it does not necessarily translate for the patients in a clinical improvement, not leading to a significant improvement in perceived quality of life.
2) In accordance with established protocols, five of the six studies included in our meta-analysis excluded only patients with a “current” diagnosis of asthma, whereas in the “Study to Understand the Safety and Efficacy of ICS Withdrawal from Triple Therapy in COPD” (SUNSET) study [
18] subjects with a history of asthma were excluded a priori (see
Table 1). The lack of a precise definition of asthma history can result in a wide range of patient profiles, from well-controlled patients with asthma to those with active asthma symptoms. Thus, the difference between protocols that exclude subjects with “current asthma” or with “history of asthma” raises methodological considerations because of the different role covered by ICS therapy in COPD subjects versus those with asthma-COPD overlap (ACO) [
34]. Although ICS withdrawal may be feasible in certain asthma phenotypes [
35], the possible inclusion of patients with ACO in studies primarily targeting COPD can significantly affect the generalizability of the findings, leading to an overestimation of the benefits of ICS therapy or an underestimate of the risks associated with discontinuation.
3) Our findings provide a small but perhaps significant addition to the debate regarding the long-term safety of ICS in COPD subjects. Previous meta-analyses have found a strong association between ICS use and the risk of pneumonia [
7,
36]. With the limitations imposed by the paucity of available studies, we found no safety concern for triple therapy versus LABA-LAMA de-escalation. This may be an important issue that needs to be further addressed in the future, especially in more targeted populations, including those with varying disease severity and exacerbation patterns. Our divergent results with the existing literature denote an urgent need for well-powered trials to identify COPD patients in whom the advantages of ICS substantially outweigh the risks.
4) The clinical significance of blood eosinophil levels in COPD is a subject of ongoing debate. Since the 2019 GOLD report [
37] to the latest [
1], the peripheral blood eosinophil count has been stated as a parameter for guiding or modifying COPD treatment, including the use of ICS-based regimens. As observed in RCTs, in COPD patients not receiving ICS-containing regimens, the likelihood of exacerbation increases with increasing eosinophil blood counts [
38,
39]. Conversely, in the FLAME study, the correlation between ICS therapeutic response and blood eosinophil level was not significant in COPD patients when comparing ICS/LABA to LABA/LAMA regimens in terms of exacerbation reduction. The LABA/LAMA combination was as effective as ICS/LABA in reducing exacerbation rates, regardless of the baseline eosinophil count (<2% or ≥2%) [
40,
41]. This is in contrast to the results of our quantitative analysis aggregating the results of the WISDOM and SUNSET trials [
16,
18], which form the basis of the most recent recommendations. For example, the European Respiratory Society (ERS) indicates a conditional recommendation for the withdrawal of ICS in patients with COPD without a history of frequent exacerbations and a strong recommendation not to withdraw ICS in patients who have a blood eosinophil count ≥ 300 eosinophils/μL, irrespective of the history of exacerbations [
42]. Analogously, the American Thoracic Society’s guidelines do not advocate for or against the use of inhaled corticosteroids as an add-on therapy to long-acting bronchodilators for COPD patients with blood eosinophilia, except for those with a history of exacerbations [
2]. The absence of a definitive recommendation underscores the need for further research in this area.
This study has several limitations. First, there is significant methodological heterogeneity among the included studies such as protocols of ICS withdrawal (abrupt or stepwise), inclusion of subject with history of asthma and history of exacerbations in the previous 12 months. Second, the non-interventional design of the real-world studies included introduces potential biases that could influence outcomes, such as physician judgment in continuing or withdrawing ICS. Third, the varying duration of triple therapy prior to study enrollment and differences in the administration of ICS, LABA, and LAMA—whether in single or separate inhalers—could contribute to differential benefits observed across studies. Fourth, the varying duration of follow-up ranging from six and 12 months which may have been inadequate to observe the outcomes. These limitations highlight the need for greater methodological consistency in future research to facilitate more reliable comparisons and robust conclusions.