Lung function in idiopathic pulmonary fibrosis - extended analyses of the IFIGENIA trial
- Jürgen Behr1_815Email author,
- Maurits Demedts2_815,
- Roland Buhl3_815,
- Ulrich Costabel4_815,
- Richard PN Dekhuijzen5_815,
- Henk M Jansen6_815,
- William MacNee7_815,
- Michiel Thomeer2_815,
- Benoit Wallaert8_815,
- Francois Laurent9_815,
- Andrew G Nicholson10_815,
- Eric K Verbeken2_815,
- Johny Verschakelen2_815,
- CDR Flower11_815,
- Stefano Petruzzelli12_815,
- Paul De Vuyst13_815,
- van den JMM Bosch14_815,
- Eulogio Rodriguez-Becerra15_815,
- Ida Lankhorst16_815,
- Marco Sardina16_815,
- Gabrielle Boissard16_815 and
- the Ifigenia study group*
© Behr et al. 2009
Received: 12 June 2009
Accepted: 27 October 2009
Published: 27 October 2009
The randomized placebo-controlled IFIGENIA-trial demonstrated that therapy with high-dose N-acetylcysteine (NAC) given for one year, added to prednisone and azathioprine, significantly ameliorates (i.e. slows down) disease progression in terms of vital capacity (VC) (+9%) and diffusing capacity (DLco) (+24%) in idiopathic pulmonary fibrosis (IPF). To better understand the clinical implications of these findings we performed additional, explorative analyses of the IFGENIA data set.
We analysed effects of NAC on VC, DLco, a composite physiologic index (CPI), and mortality in the 155 study-patients.
In trial completers the functional indices did not change significantly with NAC, whereas most indices deteriorated with placebo; in non-completers the majority of indices worsened but decline was generally less pronounced in most indices with NAC than with placebo. Most categorical analyses of VC, DLco and CPI also showed favourable changes with NAC. The effects of NAC on VC, DLco and CPI were significantly better if the baseline CPI was 50 points or lower.
This descriptive analysis confirms and extends the favourable effects of NAC on lung function in IPF and emphasizes the usefulness of VC, DLco, and the CPI for the evaluation of a therapeutic effect. Most importantly, less progressed disease as indicated by a CPI of 50 points or lower at baseline was more responsive to therapy in this study.
Registered at http://www.ClinicalTrials.gov; number NCT00639496.
Idiopathic pulmonary fibrosis (IPF) is a distinct clinical and histopathologic entity, which accounts for approximately two thirds of the idiopathic interstitial pneumonias (IIP), and is associated with a high median mortality of 50% within 3 to 5 years [1–5]. The cause of this disease is unknown [4, 6]. In the absence of a satisfactory treatment - except for lung transplantation in selected patients - the joint consensus statement on IPF by the American Thoracic Society and the European Respiratory Society suggested prednisone plus azathioprine (or cyclophosphamide) as potential treatment for IPF . Based on this statement the recently published IFIGENIA trial used prednisone plus azathioprine as a standard treatment for all patients who were randomly assigned to receive additionally high-dose N-acetylcysteine (NAC) or placebo . A treatment effect in favour of NAC was observed with a statistically significant smaller decrease of vital capacity (VC) (9%) and diffusing capacity (DLco) (24%) , which was in line with a previous observation . However, in view of a drop-out rate of ca. 30% (including deaths) questions have been raised regarding the clinical relevance and robustness of the treatment effect . These appropriate questions prompted us to perform additional, exploratory analyses of the data set. We evaluated subgroups of completers versus non-completers for differences in treatment response. We also calculated the Composite Physiologic Index (CPI), which uses the individual values for VC (% pred.), DLco (% pred.) and FEV1 (% pred.) to calculate the extent of fibrosis according to an empirically developed equation . Based on low or high baseline CPI we compared treatment effects on patients with less progressed or progressed disease. We think that these additional exploratory analyses of the IFIGENIA data set offer a unique opportunity to provide insight into the clinical course of the disease, to describe the potential clinical benefit of antioxidant therapy using NAC, and to explore the influence of disease severity at baseline on outcome.
Using data from the IFIGENIA trial , we performed a series of exploratory analyses of physiologic variables and characteristics in patients receiving prednisone and azathioprine as suggested by the ATS/ERS Statement  plus either high-dose NAC or placebo. The IFIGENIA study was a multinational, double-blind, randomized, placebo-controlled, parallel-group trial. Study treatment consisted of NAC (Zambon Group) 600 mg effervescent tablets t.i.d. or matched placebo. Patients (18 to 75 years) with a histological or radiological pattern typical for usual interstitial pneumonia (UIP) [1, 5] were included after active exclusion of other diseases [4, 7]. Patients were excluded in whom the standard regimen with prednisone and azathioprine was contraindicated or not justified (i.e. in stable patients) (full in- and exclusion criteria see reference ).
The study was conducted according to GCP-ICH guidelines goverend by the Declaration of Helsinki and by national regulations. The protocol was approved by the local ethics committees. All patients gave written informed consent and were free to withdraw at any time. Regular monitoring and sample audits were performed at the centers throughout the study. The study was designed and analysed by 19 academic physicians experienced in idiopathic pulmonary fibrosis, 1 independent statistician, and three representatives of the sponsor. The sponsor held the data but placed no limitations on study design, data analysis, or the content of the manuscript. The main statistical analysis was performed by an independent statistical company (Innopharma, Milan, Italy).
Setting, Participants, and Randomization
Between March 2000 and July 2002 184 patients were screened in 36 centers from six countries. Out of 182 eligible patients twenty-seven were not included in the analysis: 5 patients withdrew consent before starting treatment and 22 (12%) were excluded because the IPF-diagnosis was not confirmed by the radiology or histology expert committee . Of the 155 patients included in the analysis, 80 patients had been randomized to NAC and 75 to placebo. There were no significant differences in baseline characteristics .
Of these 155 patients, 108 (70%) completed the one year study (57 on NAC, 51 on placebo). At baseline 8 patients on NAC and 2 on placebo used long-term oxygen therapy (LTOT); during the study, 3 additional patients on NAC and 11 on placebo were started on LTOT. Forty-seven patients (30%) did not complete the one year study: 32 patients (21%) withdrew for various reasons (16 on NAC and 16 on placebo) and 15 (10%) died during the study: 7 (9%) on NAC, and 8 (11%) on placebo (p = 0.69).
Vital capacity (VC), forced expired volume in 1 sec (FEV1) and single-breath CO-diffusing capacity (DLco) were measured and cardiopulmonary exercise testing was performed according to ERS guidelines [11, 12].
The composite physiologic index (CPI) was calculated : CPI = 91.0 - 0.65 × DLco(%pred) -0.53 VC(%pred) + 0.34 FEV1(%pred). CPI is in-between 20 and 80 points, higher points indicating more fibrosis and poorer prognosis.
As in the previous publication  the main statistical analysis was based on a stepwise, fixed-effects analysis of covariance using an iterative procedure including the change from baseline as response variable, treatment and country factors as fixed effects, baseline value as covariate and following potential cofactors: smoking history (current/ex-smokers vs. never-smokers), age (<65 years vs. ≥ 65 years), duration of disease since diagnosis (≤ 6 vs. >6 months), DLco(≤ 40% vs. >40% predicted), VC (≤ 60% vs. >60% predicted), sex (male vs. female), and whether a biopsy had been performed. This former model was also used for the analysis of the composite physiologic index (CPI). For the analysis of CPI changes from baseline, according to categorised baseline CPI, an ANOVA model was used, including treatment and baseline CPI category as fixed factors (basal CPI: ≤ 50; >50) and their interaction; the cut-off value of 50 for basal CPI approximated the median of baseline CPI (52.26). Using the median itself did not impact on the results. Changing CPI cut-offs by steps of one and five points, respectively, turned out to show that a CPI of 50 points as cut-off appeared to be optimal.
The analyses were based, as for the main analysis, on data from all randomized patients who met the inclusion criteria for the study, received the trial medication at least once, and underwent at least baseline observation. Missing data were replaced by the last observation-carried-forward (LOCF) method for all patients who underwent at least one lung-function measurement after baseline . As the data were reanalysed minor changes from the original results occurred based on differences in adjustments with baseline and covariates as well as rounding during calculations. As a descriptive analysis the course of completers and non-completers was evaluated with respect to treatment arm; the completer subset included all patients with an assessment available at the 12 months final visit, whereas non-completers were either drop-outs or patients with a missing 12 months assessment.
Cardio-pulmonary exercise test derived variables were analysed including only treatment as fixed effect and the baseline value as a covariate.
For categorical analysis of lung function indices using variable cut-off values, comparisons between NAC and placebo were performed using 2-sided Fisher exact tests. No adjustment for multiple testing was performed, these analyses being considered as exploratory.
Analysis of VC, DLco, and CPI: last-observation-carried-forward (LOCF) vs. Completers and Non-Completers
Baseline Characteristics of Completers and non-Completers:
Completers (N = 106)
Non completers (N = 33)
All patients [n(%)]
Duration of symptoms (Month)
New diagnosis? [n(%)]
Surgical lung biopsy [n(%)]
Baseline VC [l]
Baseline DLCo [mmol/min/kPa]
Baseline TLC [l]
Baseline PaO 2 [mmHg]
Baseline P(A-a)O 2 [mmHg]
LOCF-method vs. Completers/non-Completers analyses of VC, DLco, and CPI: changes between last measurement and base line
Change from baseline †
VC (% pred.)
When formally assessing the differences between treatment arms (ANCOVA model), a significant effect on VC of 0.18 ± 0.07 L and 4.80 ± 2.00% pred. was found when using the LOCF method (p = 0.017). For the completers the effect was smaller (0.09 ± 0.09 L, p = 0.34 and 1.93 ± 2.41% pred., p = 0.42) and more pronounced in non-completers (0.22 ± 0.13 L, p = 0.099 and 7.26 ± 3.80% pred., p = 0.069). For the DLco measurements NAC had a statistically significant treatment effect in the completer subset for absolute change and for % predicted (1.106 ± 0.377 mmol/min/kPa, p = 0.0044 and 7.10 ± 2.64% pred., p = 0.0087, respectively), but not so in the small non-completer subset (0.380 ± 0.228 mmol/min/kPa, p = 0.11 and 3.573 ± 2.764% pred., p = 0.21).
We also calculated and analysed the Composite Physiological Index (CPI) . At baseline CPI mean ± SD was similar in NAC vs. placebo treated patients (52.6 ± 9,8 vs. 50.93 ± 10.2, n.s.). An increase of the CPI indicates disease progression and was observed in the placebo group using the LOCF method and also in the completer and non-completer subsets using placebo, whereas NAC-treated patients did not show significant disease progression in terms of the CPI in the LOCF and completer subsets (table 2). In the non-completers disease progression occurred with both, NAC (p = 0.010) and placebo (p < 0.0001)(table 2). Again, the formal analysis of the treatment effect between groups (ANCOVA model) was significant in favour of NAC when using the LOCF method (-4.962 ± 1.607, p = 0.0025) and in the completer subset (-6.151 ± 2.137, p = 0.0052); in the smaller non-completer subset the same trend occurred (-3.014 ± 2.201, p = 0.20).
Analysis of cardio pulmonary exercise testing: LOCF vs. Completers and Non-Completers
LOCF-method vs. Completers/non-Completers analyses of cardio pulmonary exercise test derived variables: changes between last measurement and baseline
V'O2max (% pred.)
Categorical analysis of VC, DLco and CPI and effect of baseline value of CPI
Influence of baseline CPI on outcome
Analysis of patients who survived/died
Of the total population of 155 patients 15 (10%) died; of these 7 (9%) were in the NAC arm and 8 (11%) in the placebo arm. Only four out of 15 patients who died (26.7%) had significant deterioration of PFT as defined in the ATS/ERS-statement  prior to death, whereas eight (53.3%) died within three months of treatment initiation without follow-up PFTs; 4 of these latter 8 patients died from cardiac disease, 3 succumbed to overwhelming infection, and one died from respiratory failure. Analysis of patients who survived or died with NAC or placebo showed no statistically significant differences in baseline demographics between the four groups. However, P(A-a)O2 and CPI were significantly higher at baseline in those patients who died during the study (data not shown).
This study extends the analysis of our previously published IFIGENIA study  by categorical analysis of lung function indices and description of completer/non-completer subsets. In addition we analysed the composite physiologic index (CPI) which was especially designed and validated to represent disease extent on HRCT and to correct for coexisting emphysema and which has also been shown to be a predictor of prognosis [10, 13]. The CPI has advantages over scoring system as proposed by Watters et al  and by King et al.  because it is easier to generate, requiring solely the measurement of VC, FEV1 and DLco, and predicts survival more consistently [10, 13].
When analysing the effects of NAC on VC, DLco, maximal exercise indices, and the CPI we found that in completers none of the indices deteriorated significantly with NAC, but most indices did with placebo; in non-completers the majority of indices worsened at a much lesser extent with NAC than with placebo. Importantly, we did not observe divergent signals from the completers and non-completers subgroups regarding treatment effects. Correspondingly, categorical changes in VC, DLco and CPI showed globally significantly better results with NAC than with placebo.
Our data indicate that the effects of NAC on VC, DLco and CPI were significantly better if the baseline CPI was low (≤ 50 points), i.e. in the less severe cases. This finding is in line with findings from previous studies and may suggest the presence of specific disease processes in severe disease states [15–18].
With respect to the clinical relevance of the changes observed several authors have demonstrated in IPF cohorts that small changes of FVC or DLco during the first 6 to12 months eventually result in major survival differences during the following years [13, 19–22]. Consequently, small treatment effects achieved with high dose NAC therapy may impact survival significantly in the long run . A long-term clinical trial testing NAC in IPF is clearly warranted.
Regarding IPF mortality it should be noted that lung function deterioration could be documented before death only in a minority of patients (26,7%), whereas the majority of patients (53.3%) died with rapid deterioration within three months of treatment not allowing for control lung function measurements before death. This may imply that a decline of lung function does not precede a fatal disease exacerbation, as hypothesized previously  or simply that the intervals at which control measurements of lung function were scheduled were too long. This should be considered in future studies. A considerable number of patients died from coexisting cardiac disease. This observation should draw attention to potential comorbidities like coronary artery and left heart diseases as well as pulmonary hypertension associated with IPF which may warrant specific treatment approaches .
There are limitations of our study. The completers/non-completers groups used for comparisons do not represent predefined and stratified subgroups. Therefore, the groups differ e.g. with respect to baseline lung function. On the other hand it is not surprising and reassuring that the non-completer group presented worse baseline values. The explorative statistical analysis presented here was done without correction for multiple testing, thus limiting its use for clinical decision making. Moreover, our data do not allow firm conclusions to be drawn on whether the treatment effects observed are contributable to NAC alone or can be achieved only when using triple therapy of prednisone, azathioprine, and high-dose NAC. Finally, it may be argued that intention to treat is the only acceptable study design; although we do not question this dictum for the pivotal analysis, additional exploratory analyses, as the one presented here, may allow a better understanding of the data structure and robustness and may help to generate new hypothesis and should, therefore, also be made accessible.
Taken together the data presented here corroborate the results of the pivotal paper  and support the use of high-dose NAC in patients with IPF. Although the effect size appears relatively small, the lack of serious side effects allows a positive risk-to-benefit assessment. Notably, our present analysis suggests that patients with less progressed disease (CPI ≤ 50 points) may have a more favourable response. Consequently, "triple therapy" - prednisone, azathioprine plus high-dose NAC - is a seizable treatment option for IPF patients. Referring to the available evidence the recent ILD Guideline published by the British Thoracic Society incorporated a weak recommendation (C) in favour of high-dose NAC in combination with prednisone and azathioprine for IPF patients .
The authors are grateful to IFIFGENIA Study Group: Steering Committee: M. Demedts (Chairman), J. Behr, R. Buhl, U. Costabel, P.N.R. Dekhuijzen, H.M. Jansen, W. MacNee, B. Wallaert, M. Thomeer; HRCT Scientific Committee: C.D.R. Flower, F. Laurent, J. Verschakelen; Histology Scientific Committee: A.G. Nicholson, E.K. Verbeken, F. Capron; Country Coordinators: J. Behr, J.M.M. van den Bosch, P. De Vuyst, E. Rodriguez-Becerra, S. Petruzzelli, B. Wallaert; Zambon Group [* means no more active]: Clinical Trial Coordinator: G. Corvasce*, A. Peviani; Medical Dept: I. Lankhorst* E. Makin*, L. Licciardello, S. Bellinvia*, C. Di Padova, M. Sardina, N. Kormoss, P. Boulanger, A. Esteras; Data Coordination: F. Sirtori; Drug Safety: G. Moroni; Biostatistics: G. Boissard, A Ardia* and M Montanari; Active participating Centres and Clinical Investigators: BELGIUM: M. Demedts, M. Thomeer, U.Z. Gasthuisberg, Leuven; H. Slabbynck, Alg. Ziekenhuis Middelheim, Antwerpen; E. Michiels, Z.O.L. Campus St. Jan, Genk; P. De Vuyst, Free University of Brussels, Erasmus Hospital, Brussels; FRANCE: B. Wallaert, N. Just, C.H.R.U. de Lille, Hôpital Calmette, Lille; J. F. Muir, Hôpital de Bois Guillaume, Rouen; Ph. Delaval, Hôpital Pontchaillou, Rennes; P. Chanez, A. Bourdin, Hopital Arnaud de Villeneuve, Montpellier; J. Cadranel, Hôpital Tenon, Paris; Ph. Camus, CHU Le Bocage, Dijon; GERMANY: U. Costabel, H. Steveling, Ruhrlandklinik, Essen-Heidhausen; J. Behr, R. Baumgartner, University of München, Klinikum Grosshadern, München; R. Buhl, III. Medizinische Klinik, Klinikum der Johannes Gutenberg-Universität, Mainz; J. Müller-Quernheim, Forschungzentrum Borstel, Medizinische Klinik, Borstel; R. Loddenkemper, Lungenklinik Heckeshorn, Klinikum Zehlendorf, Berlin; T. Welte, Zentrum für Innere Medizin, Universitäts Klinikum Magdeburg, Magdeburg; A. Meyer, Universitäts Krankenhaus Eppendorf, Hamburg; R. Bonnet, I. Mäder, Zentralklinik Bad Berka GmbH, Bad Berka; ITALY: G. Simon, Azienda Ospedaliera Villa Sofia, Palermo; G. Bottino, DIMI - Università di Genova, Genova; C. Giuntini, Dipartimento Cardiotoracico, Università degli Studi di Pisa, Pisa; A. Rossi, IRCCS Policlinico S. Matteo, Pavia; S. Gasparini, Ospedale Torrette, Torrette di Ancona; M. Dottorini, Ospedale "R. Silvestrini", Perugia; G. Anzalone, Ospedale di Prato, Prato; G. Bustacchini, Ospedale S. Maria delle Croci, Ravenna; SPAIN: E. Rodríguez-Becerra, Hospital Universitario Virgen del Rocío, Sevilla; L. Callol Sanchez, Hospital Universitario Del Aire, Madrid; J. Ancochea Bermudez, Hospital Universitario de la Princesa, Madrid; J. M. Rodriguez-Arias, l. Vigil, Hospital Sant Pau, Barcelona; J. L. Llorente, Hospital De Cruces, Baracaldo-Bilbao; THE NETHERLANDS: J. van den Bosch, St. Antonius Ziekenhuis, Nieuwegein; F. Beaumont, Bosch Medicentrum, Lok. Grootziekengasthuis, Hertogenbosch; H.M. Jansen, Academic Medical Center, Amsterdam; F.J.J. van den Elshout, Ziekenhuis Rijnstate, Arnheim; M. Drent, Academisch Ziekenhuis Maastricht, Maastricht.
The excellent support from G. Corvasce, A. Ardia, and M. Montanari for the conduct of the trial, for statistical analyses, and for preparation of the manuscript is gratefully acknowledged. The study was funded by Zambon Group, Bresso, Milan, Italy
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