Table of Contents
2. Treatment of Cystic Fibrosis
3. Treatment of Pulmonary Exacerbations
4. Pulmonary Complications
5. Lung Transplantation
7. About the Author
Cystic fibrosis (CF) is a genetic disease which is usually caused by the absence, dysfunction or reduced number of the multifunctional CF transmembrane regulator (CFTR) protein.. Recently new therapy approaches such as ivacaftor have emerged which target the cause of the condition itself. This white paper focusses only on the current treatment of pulmonary complications of CF.
Cystic fibrosis causes pulmonary symptoms to appear early in life. These include airway inflammation and impaired mucociliary clearance leading to consequent chronic infection of the airways with polymorphonuclear cells present in the bronchoalveolar lavage fluid obtained from even healthy-looking infants with CF. There is progressive decline of lung function, specifically forced expiratory volume in 1 second (FEV1), with episodes of acute worsening of respiratory symptoms, often referred to as “pulmonary exacerbations”. Waters and co-workers1 have recently shown for the first time that pulmonary exacerbations are responsible not only for half of FEV1 decline, but also that the time between consecutive exacerbations plays an important part in this long-term lung function decline1 (Waters 2012). Due to their persistency and chronicity, these episodes progress to bronchiectasis, gas trapping, hypoxemia and hypercapnia becoming the hallmark of cystic fibrosis lung disease. Pulmonary complications of CF are responsible for 85% of the mortality of these patients. Clinical features of a pulmonary exacerbation may include increase cough, wheezing, increased sputum production, shortness of breath, chest pain, loss of appetite, loss of weight and lung function decline.
After a rapid colonization by Haemophilus influenza or Staphylococcus aureus, at the beginning of the disease, within a short time Pseudomonas aeruginosa becomes the predominant organism found in the airways of these patients. Another organism that can cause colonization without invasive infection is Aspergillus fumigatos. An intensive allergic response to this fungus, known as allergic bronchopulmonary aspergillosis (ABPA) is seen in 1-15% of patients with CF with a frequency that varies geographically. Persistent infections enhance the genetic defect that induces dehydration of the airway surface liquid and impairs mucociliary clearance; as a result individuals with CF have difficulty clearing pathogens from the lung and experience chronic pulmonary infections and inflammation.
2. Treatment of Cystic Fibrosis
Newly introduced therapies and aggressive management of the lung disease have resulted in great improvement in length and quality of life, with the result that the median expected survival age has reached 36 years. The recommendation of an aggressive approach is supported by the evidence coming from two epidemiological studies showing that cystic fibrosis centres with high median pulmonary function test results saw patients more frequently, obtained more frequent respiratory-tract cultures and used more oral and intravenous antibiotics than did centres with lower median lung function results2,3. The US Cystic Fibrosis Foundation gave the highest recommendation for chronic pulmonary CF therapy for inhaled dornase alfa (recombinant human DeoxyriboNuclease: given daily) and for inhaled tobramycin (300 mg twice daily given in 28-day on-off cycles for use in patients with moderate to severe disease with P. aeruginosa in their airways)4. Even though evidence supporting the benefit of these two treatments in patients with CF with milder lung disease are less robust the US Cystic Fibrosis Foundation guidelines however recommend their use. Other treatments supported by this guideline are inhaled hypertonic saline, chronic azithromycin, ibuprofen and inhaled β2-agonists in specific patient populations.
Inhaled dornase alfa (recombinant human DeoxyriboNuclease)
Inhaled dornase alfa was developed to degrade the large amount of free DNA that accumulate within CF mucus, thereby improving the viscoelastic properties of airway secretions and promoting airway clearance. Its chronic use is strongly recommended on the basis of good quality evidence derived from both short and long term studies with large numbers of patients recruited. Long term studies uniformly demonstrated improvement in lung function: increased 5.8 % compared with placebo after 24 weeks of therapy in one study5 and 7.3% in patients with severe CF lung disease treated for 12 weeks in another6. In all the studies dornase alfa was well tolerated with very few adverse events.
Aerosolized antibiotics have been advocated both for eradication of initial infection and for suppression of chronic infections of the most common bacteria isolated in sputum of CF patients, particularly Pseudomonas aeruginosa. Perhaps the most commonly used inhaled antibiotic is tobramycin. Outcomes measured in tobramycin studies were both lung function FEV1 assessment and prevention of pulmonary exacerbations. In three studies with 619 patients in total in comparison with placebo and standard treatment, significant improvements in FEV1 ranging from 7.8 to 12% were shown7,8,9. Ramsey and coworkers found that inhaled tobramycin produced a 26% reduction in hospitalization and a 36% reduction in the use of intravenous antipseudomonal antibiotics compared to placebo. In another study the total number of days spent in hospital for exacerbation treatment was less in patients treated with inhaled tobramycin in comparison with placebo8. On the basis of this compelling evidence, the recommendation of the benefit of tobramycin was extended also to CF patients with mild disease.
Pulmonary Cystic Fibrosis
Other inhaled antibiotics are used to treat patients with cystic fibrosis, including aztreonam, which was approved by the FDA in 2010 and colistin. Both are used to treat Pseudomonas aeruginosa infection.
Inhaled hypertonic saline, as a hyperosmolar agent, has been proposed as a therapy to increase hydration (drawing water into the airways) of the surface liquid of the airways (periciliary layer) in patients with CF, thereby improving mucociliary clearance. Elkins and colleagues, for example, in their large multicenter study found that patients with CF who received 4 ml of 7% hypertonic saline twice daily via nebulisation for 48 weeks had a larger increase in FEV1 and fewer pulmonary exacerbation than patients who receive normal (0.9%) saline10.
Macrolide antibiotics have been used with good results in diffuse panbronchiolitis, a disease that shares similarities with pulmonary CF. The mechanism of action may be related to either the antimicrobial or anti-inflammatory properties of these agents or perhaps to both. In the largest of the four studies conducted with the chronic use of macrolides in CF, FEV1 was improved and pulmonary exacerbations reduced after treatment with thrice weekly azithromycin compared to placebo11.
Both short acting and long acting inhaled β2-agonists have been tested in CF trials. The short acting inhaled β2-agonist salbutamol has been administered at daily doses ranging from 80 to 600 μg by metered dose inhaler or from 0.5 to 5mg by nebulizer while long acting inhaled β2-agonist, salmeterol, has been administered at daily doses ranging 84 to 336μg by metered dose inhaler. Inhaled β2-agonists consistently demonstrated an improvement in lung function in short term studies ranging from 2 days to 4 weeks; this benefit was not however confirmed in long term studies. When inhaled long acting β2-agonists were compared with short acting β2-agonists a greater improvement on FEV1 was found. These positive results were not repeated when a short acting anticholinergic drug, ipratropium bromide, was used.
As inflammation is one of the pathophysiological features of the airways in CF, anti- inflammatory therapies are often used in the treatment of these patients. It is thought that excessive and persistent inflammation that characterizes the airways of patients with CF is a major cause of airway destruction over time leading to bronchiectasis and severe obstructive airway disease.
- Non steroidal anti-inflammatory drugs (NSAID). High dose oral ibuprofen has been studied in two large long-term placebo controlled trials. Konstans and colleagues in a single centre study showed a decrease in the rate of loss of lung function over 4 years in comparison with placebo, with the largest benefit seen in younger patients aged 5-13 years12. In one Canadian multi centre study, Lands and co-workers showed no significant effect of ibuprofen treatment on FEV1 compared to placebo, although the ibuprofen-treated group spent fewer days in the hospital than patients in the placebo group13.
- Inhaled Corticosteroid (ICS). Some ICSs have been evaluated in the treatment of CF in studies with lung function decline and pulmonary exacerbation frequency as endpoints. Results of studies with beclomethasone, fluticasone and budesonide have been negative. Therefore, ICS therapy is not recommended for the treatment of CF.
- Oral corticosteroids. No convincing evidence was found in studies conducted with oral corticosteroids given in an alternate day dosing schedule. Although some benefits on lung function have been reported, such therapy has been associated with adverse events related to steroid treatment which result in a net negative effect for the patients.
3. Treatment of Pulmonary Exacerbations
Treatment for pulmonary exacerbations of cystic fibrosis generally includes inhaled, intravenous or oral antibiotics, increased use of airway clearance techniques and improved nutrition14.
Combination antibiotic treatment with agents that have different modes of action is preferred to single agent treatment to avoid the emergence of resistant strains, with treatment lasting about 14 days. Since most patients with exacerbations will have P. aeruginosa in their airways, the usual in-hospital treatment is a combination of a β lactam, which interferes with cell wall biosynthesis, and an aminoglycoside, which binds bacterial ribosome subunits and inhibits protein production, however addition or substitution of other antibiotics specific for S. aureus, H. influenza or meticillin-resistant S. aureus (MRSA) might be necessary. For milder exacerbations a combination of home-based treatment of an oral and inhaled antibiotic allows the patient to continue his/her daily life unimpeded.
There are many techniques that are used with CF patients to augment clearance of tenacious airway secretions. These methods include introduction of, or prescription of a more intensive regime of, treatments such as percussion and postural drainage, positive expiratory pressure (PEP) devices, high pressure PEP devices, active cycle of breathing techniques, airway-oscillating devices, high frequency chest wall oscillation devices and autogenic drainage (i.e. chest physiotherapy in which the patient produces a series of respiratory huffs and coughs designed to move mucus from distal to proximal airway so it can be coughed out).
The benefits of maintaining good nutrition in regard to long-term survival and lung health cannot be overstated, especially because of the strong correlation that exists between nutritional status and pulmonary function. Patients’ height and weight should be measured and their body-mass index (BMI) calculated at every cystic fibrosis clinic visit; those showing a decrease in BMI or stunting should receive nutritional counseling.
4. Pulmonary Complications
As airways disease worsens there is an increased likelihood of respiratory complications, such as hemoptysis and pnemothorax15. Hemoptysis is quite common in CF patients; a retrospective review reported that 9.1% of patients had hemoptysis over a 5-year period. The average annual incidence of pnemothorax is 0.64%. Both of these complications occur more commonly in older patients with advanced disease.
Hemoptysis should be treated properly with antibiotics, always admitted to the hospital when it is massive, undergo bronchial artery embolization (BAE) when hemoptysis reaches the classification of ‘massive’ (coughing up ≥ 600 mL of blood in a 24 hour period) and if the patient is clinical unstable.
Patients with CF with a large pneumothorax should be admitted to hospital and should have a chest tube placed. If pneumothorax is recurrent, such patients should undergo surgical pleurodesis to prevent recurrence. After a pneumothorax episode patients with CF should avoid flying, lifting weights and spirometry for two weeks after the pneumothorax has resolved.
5. Lung Transplantation
Lung transplantation is the final therapeutic option for CF patients with end-stage lung disease. Lung transplantation has the potential to extend and substantially improve quality of life in properly selected patients. For adults referral for transplantation generally occurs when a patient’s FEV1 plateaus at less than 30% of that predicted. However age, sex, lung infection and colonization, and a rate of decline in FEV1 all affect the decision. Use of nocturnal non-invasive ventilation can improve chest symptoms, sleep-associated hypoventilation and quality of life in patients with awake hypercapnia who are awaiting transplantation.
Today, almost 45 percent of the cystic fibrosis population is aged 18 years or older even though they still have a shorter-than-normal life expectancy. The good news is that as treatments for CF improve, the life expectancy for people with the disease is rising. Fifty years ago, children with CF often died before attending primary school. Today many people with the disease live into their 30s, 40s and beyond.
Although refinements of conventional, symptomatic therapy will continue, and probably be enhanced by the clinical engineering so popular nowadays, great leaps in survival will require entirely new approaches to therapy. Today there are more than two dozen therapies at various stages of clinical trials, a dozen of them directed at the basic defect. Probably the latter together with the identification and treatment of patients at birth, before lung damage occurs, will allow to further increase life expectancy, at least for patients whose lungs are clear enough to benefit of them.
7. About the Author
Renato Testi graduated from the University of Padua with a degree in Chemistry, before gaining his MD from the University of Verona. After a couple of years at Padua University as an assistant in the Organic
Chemistry Department, Renato joined Laboratory Glaxo S.p.A. (Italy) as Head of Chemistry from 1974 to 1979. In 1979 he moved to the Medical Department as a Medical Advisor, subsequently becoming Medical Respiratory Leader in the same company Glaxo Smith Kline SpA (Italy) from 1979 to December 2004. In this role Renato supported clinical development and marketing activities of several drugs in respiratory medicine.
In 2006, Renato became a Clinical Research Physician at Centro Ricerche Cliniche, Policlinico BG Roma, Verona focusing on performing medical activities and screening visits for volunteers involved in clinical trials in Phase I to III. Renato joined CROMSOURCE in 2010 as a Medical Monitor in the Clinical Research division. Here Renato has managed clinical trial activities, medical oversight and monitoring procedures for many international clinical trials in both asthma and COPD.
Renato continues practising as a physician specialised in respiratory medicine, currently at Unit-Policlinico BG Roma, Verona University. Renato can be contacted at email@example.com
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