Pulmonary fibrosis: rate of disease progression as a trigger for referral for lung transplantation

Pulmonary Hypertension in Interstitial Lung Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Pulmonary hypertension (PH) is a key complication in interstitial lung disease (ILD), with recent therapeutic advances.

RESEARCH QUESTION

What are the diagnostic evaluation, epidemiologic features, associated factors, prognostic significance, and outcome measures in interventional trials for PH in patients with ILD in the current literature?

STUDY DESIGN AND METHODS

Ovid MEDLINE, Embase, and CENTRAL databases were searched for original research evaluating PH in participants with ILD of any cause. The definition of PH was based on the investigators' criteria.

RESULTS

Three hundred two studies were included, with varying diagnostic evaluations used to define PH. Commonly used diagnostic tests were right heart catheterization (RHC; 56%) and transthoracic echocardiography (TTE; 50%). The pooled prevalence for PH in general populations with ILD was 36% (95% CI, 30%-42%) using RHC and 34% (95% CI, 29%-38%) using TTE. Lower diffusion capacity of the lungs for carbon monoxide, worse oxygenation status, reduced exercise capacity, increased pulmonary artery to aorta ratio and pulmonary artery diameter, and elevated serum brain natriuretic peptide consistently were associated with the presence of PH in at least 60% of reported studies. The presence of PH was associated with increased symptom burden and worse prognosis. Outcome measures in interventional trials of PH in ILD focused on changes in pulmonary vascular hemodynamics and 6-min walk distance.

INTERPRETATION

PH is a common complication in ILD with significant health impacts. A standardized definition with prospective evaluation of risk-stratified assessments for PH using identified associated risk factors is warranted. Our findings provide an evidence base for validation as surrogate end points in future PH interventional trials in ILD.

TRIAL REGISTRY

International Prospective Register of Systematic Reviews; No.: CRD42021255394; URL: https://www.crd.york.ac.uk/prospero/.

Use of 6-minute walk distance to predict lung transplant-free survival in fibrosing non-IPF interstitial lung diseases

BACKGROUND AND OBJECTIVE

The identification of progression in patients with fibrosing non-idiopathic pulmonary fibrosis (IPF) interstitial lung diseases (ILDs) represents an ongoing clinical challenge. Lung function decline alone may have significant limitations in the detection of clinically significant progression. We hypothesized that longitudinal changes of 6-min walk distance (6MWD) from baseline, simultaneously considered with measures of lung function, may independently predict survival and identifying clinically significant progression of disease.

METHODS

Forced vital capacity (FVC), diffusing lung capacity (DLCO) and 6MWD were considered both at baseline and at 1 year in a discovery cohort (n = 105) and in a validation cohort (n = 138) from different centres. The primary endpoint was lung transplant (LTx)-free survival.

RESULTS

Average follow-up was 3 years in both cohorts. Combined incidence of deaths and LTx was 29% and 21%, respectively. No collinearity and no strong correlations were observed among FVC, DLCO and 6MWD longitudinal changes. While age, gender and BMI were not significant, 6MWD decline ≥24 m predicted LTx-free-survival significantly and independently from FVC and DLCO declines, with high sensitivity and specificity, in both the discovery and the validation cohorts. Although FVC and DLCO declines remained significant predictors of LTx-free survival, 6MWD decline was more accurate than the proposed ATS/ERS/JRS/ALAT functional criteria. Results were confirmed after stratifying patients by baseline FVC.

CONCLUSION

Longitudinal declines of 6MWD are associated with poor survival in fibrosing ILDs across a wide range of baseline severity, with high accuracy. 6MWD longitudinal decline is largely independent from lung function decline and may be integrated into the routine assessment of progression.

Retrospective cohort study of patients qualified for lung transplantation due to idiopathic pulmonary fibrosis - single-centre experience

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive disease. Pharmacological treatment can only slow its progression. However, lung transplantation (LTx) is the only treatment for patients with its end-stage form. This study analysed the long-term results of the qualification process of patients with IPF recruited for LTx in a single centre.

MATERIAL AND METHODS

Retrospective analysis of 84 patients (56 patients who died while on the waiting list and 28 patients who underwent LTx) with end-stage IPF who were qualified for LTx between 2006 and 2017 at the Silesian Centre for Heart Diseases (Zabrze, Poland).

RESULTS

Cox proportional hazard analysis showed that the only parameter was 6-minute walk test (6MWT) distance, which statistically significantly impacted the probability of receiving a graft (parameter assessment, 0.00523; p = 0.006; 95% confidence interval (CI): 0.0015-0.009; hazard ratio (HR) = 1.005) as well as that of death while on the waiting list (parameter assessment, -0.0054; p = 0.003; 95% CI: -0.009- (-0.0017); HR = 0.995). Patients with a 253-350-m 6MWT distance had 3 times greater risk of dying while on the waiting list than those who walked more than 350 m. Other factors, such as height, sex, and blood group, also influenced the outcome.

CONCLUSIONS

The 6-minute walk test distance is an independent predictor of mortality on the lung transplant waiting list. Blood type and height also play a significant role in becoming a lung recipient.

Pathology and natural history of organ fibrosis

Histopathological assessment of fibrosis focusing on morphological patterns provides important information for the management of patients with chronic diseases of the kidney, liver and the lung. This review summarizes key histopathological features of pulmonary, renal and hepatic fibrosis and discusses advances in the understanding of the pathogenesis of pulmonary fibrosis and pathogenetic insights with translational implications for renal fibrosis. The review also tackles new staging approaches based on liver fibrosis dynamics and evaluation of fibrosis regression, digital pathology and second harmonic generation microscopy methods for hepatic fibrosis assessment and critical appraisal of non-invasive tests for liver and renal fibrosis evaluation.

Outcome of lung transplantation in non-idiopathic pulmonary fibrosis interstitial lung disease

Lung transplantation remains the only curative treatment option for selected patients with end-stage interstitial lung disease (ILD). Candidate selection is impeded by patient heterogeneity, particularly in the subgroup of non-idiopathic pulmonary fibrosis (non-IPF) interstitial lung diseases. We performed a descriptive analysis of all non-IPF ILD patients who underwent lung transplantation in our center between July 1991 and November 2016 (n = 129) and searched for pre-transplant variables correlating with graft loss and chronic lung allograft dysfunction (CLAD). Our study cohort was characterized by a significantly affected medical condition, an extensive pre-transplant corticosteroid use (73.8%), and a high prevalence of pulmonary hypertension (55.7%). Earlier year of transplantation (P = .004), higher bilirubin level (P < .0001), older recipient age (P = .04), and smaller recipient height (P = .02) were found to be associated with earlier graft loss in multivariate analysis. Moreover, pre-transplant corticosteroid treatment tended to be related to earlier graft loss (P = .06), while pulmonary hypertension did not significantly correlate. None of the pre-transplant variables were shown to be associated with CLAD development. Ongoing research is required to further explore this diverse patient population and the pre-transplant variables determining their post-transplant outcome.

Lung transplantation for idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with a poor prognosis. Lung transplantation is the only intervention shown to increase life expectancy for patients with IPF, but it is associated with disease-specific challenges. In this Review, we discuss the importance of a proactive approach to the management of IPF comorbidities, including gastro-oesophageal reflux, pulmonary hypertension, coronary artery disease, and malignancy. With a donor pool too small to meet demand and unacceptably high mortality on transplant waiting lists, we discuss different systems used internationally to facilitate organ allocation. We explore the rapidly evolving landscape of transplantation for patients with IPF with regards to antifibrotic therapy, technological advances in extracorporeal life support, advances in understanding of the genetics of the disease, and the importance of a holistic multidisciplinary approach to care. Finally, we consider potential advances over the next decade that are envisaged to improve transplantation outcomes in patients with advanced IPF.

Lung allocation

Shortage of donor lungs in most western countries and broadening of indications for lung transplantation (LTx) has led increased waiting list mortality in the past. Usually donor lungs and recipients are matched by size as measured by total lung capacity and blood type in first order. In some countries regional allocation comes first, in other countries a national wait list exists and some nations are organized in supranational allocation systems. Organ distribution should respect the ethical principles of equity, justice, beneficence and utility. Generally, top priority on the list should be given to patients with the least amount of time to live but outcome is an important factor to consider to avoid futile transplantations. Installation of an urgency status will decrease mortality of the sickest candidates on the waitlist unless the proportion of patients on urgency status will be too high. Urgency can be determined by clinical judgment (so called center decision), an audit process or objectively by a score system. Among the 3,500 transplants performed worldwide annually, approximately 60% are allocated by lung allocation score (LAS) (US, Germany, the Netherlands). With the LAS a model for survival prediction after lung transplantation and wait list survival probability was created. Clinical experience in the US since 2005 and in Germany since 2011 favourable reports regarding effects on waiting list outflow, transplant activity and outcomes have been published. Future perspectives will focus on broader geographic sharing, updating and further development of the LAS.

Mortality on the Waiting List for Lung Transplantation in Patients with Idiopathic Pulmonary Fibrosis: A Single-Centre Experience

PURPOSE

Lung transplantation (LTX) is nowadays accepted as a treatment option for selected patients with end-stage pulmonary disease. Idiopathic pulmonary fibrosis (IPF) is characterized by the radiological and histologic appearance of usual interstitial pneumonia. It is associated with a poor prognosis, and LTX is considered an effective treatment to significantly modify the natural history of this disease. The aim of the present study was to analyse mortality during the waiting list in IPF patients at a single institution.

METHODS

A retrospective analysis on IPF patients (n = 90) referred to our Lung Transplant Program in the period 2001-2014 was performed focusing on patients' characteristics and associated risk factors.

RESULTS

Diagnosis of IPF was associated with high mortality on the waiting list with respect to other diagnosis (p < 0.05). No differences in demographic, clinical, radiological data and time spent on the waiting list were observed between IPF patients who underwent to LTX or lost on the waiting list. Patients who died showed significant higher levels of pCO2 and needed higher flows of O2-therapy on effort (p < 0.05). Pulmonary function tests failed to predict mortality and no other medical conditions were associated with survival.

CONCLUSIONS

Patients newly diagnosed with IPF, especially in small to medium lung transplant volume centres and in Countries where a long waiting list is expected, should be immediately referred to transplantation, delay results in increased mortality. Early identification of IPF patients with a rapid progressive phenotype is strongly needed.

Lung transplantation in idiopathic pulmonary fibrosis: a systematic review of the literature

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a distinct form of interstitial pneumonia with unknown origin and poor prognosis. Current pharmacologic treatments are limited and lung transplantation is a viable option for appropriate patients. The aim of this review was to summarize lung transplantation survival in IPF patients overall, between single (SLT) vs. bilateral lung transplantation (BLT), pre- and post Lung Allocation Score (LAS), and summarize wait-list survival.

METHODS

A systematic review of English-language studies published in Medline or Embase between 1990 and 2013 was performed. Eligible studies were those of observational design reporting survival post-lung transplantation or while on the wait list among IPF patients.

RESULTS

Median survival post-transplantation among IPF patients is estimated at 4.5 years. From ISHLT and OPTN data, one year survival ranged from 75% - 81%; 3-year: 59% - 64%; and 5-year: 47% - 53%. Post-transplant survival is lower for IPF vs. other underlying pre-transplant diagnoses. The proportion of IPF patients receiving BLT has steadily increased over the last decade and a half. Unadjusted analyses suggest improved long-term survival for BLT vs. SLT; after adjustment for patient characteristics, the differences tend to disappear. IPF patients account for the largest proportion of patients on the wait list and while wait list time has decreased, the number of transplants for IPF patients has increased over time. OPTN data show that wait list mortality is higher for IPF patients vs. other diagnoses. The proportion of IPF patients who died while awaiting transplantation ranged from 14% to 67%. While later transplant year was associated with increased survival, no significant differences were noted pre vs. post LAS implementation; however a high LAS vs low LAS was associated with decreased one-year survival.

CONCLUSIONS

IPF accounts for the largest proportion of patients awaiting lung transplants, and IPF is associated with higher wait-list and post-transplant mortality vs. other diagnoses. Improved BLT vs. SLT survival may be the result of selection bias. Survival pre- vs. post LAS appears to be similar except for IPF patients with high LAS, who have lower survival compared to pre-LAS. Data on post-transplant morbidity outcomes are sparse.

Current status of lung transplantation

Lung transplantation is a well-established treatment option for selected patients with end-stage lung disease, leading to improved survival and improved quality of life. The last 20 years have seen a steady growth in number of lung transplantation procedures performed worldwide. The increase in clinical activity has been associated with tremendous progress in the understanding of cellular and molecular processes that limit both short- and long-term outcomes. This review gives a comprehensive overview of the current status of lung transplantation for the referring physician. It demonstrates that careful selection of potential recipients, optimisation of their condition prior to transplant, use of carefully assessed donor organs, excellent surgery and meticulous long-term follow-up are all essential ingredients in determining a successful outcome.

Pirfenidone treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a discrete clinicopathologic entity defined by the presence of usual interstitial pneumonia on high-resolution CT scan and/or open lung biopsy and the absence of an alternate diagnosis or exposure explaining these findings. There are currently no FDA-approved therapies available to treat this disease, and the 5-year mortality is ∼80%. The pyridone derivative pirfenidone has been studied extensively as a possible therapeutic agent for use in this deadly disease. This review will present the unique clinical features and management issues encountered by physicians caring for IPF patients, including the poor response to conventional therapy. The biochemistry and preclinical efficacy of pirfenidone will be discussed along with a comprehensive review of the clinical efficacy, safety, and side effects and patient-centered foci such as quality of life and tolerability. It is hoped that this information will lend insight into the complex issues surrounding the use of pirfenidone in IPF and lead to further investigation of this agent as a possible therapy in this devastating disease.