Respiratory
Etiology
Pulmonary toxicity most likely secondary to:
- DNA damage from the drug or RT
- Damage inflicted by free radical generation
- Allergic response to the cytotoxic agent
- Subsequent injury induced by the inflammatory response to the primary damage
Pulmonary Fibrosis
The underlying pathogenic mechanism which may precipitate much of the pulmonary damage arising from cancer treatment can arise from collagen deposits that occur after cellular damage.
Breakdown of lung tissue can trigger an inflammatory reaction that activates the increased production of elastin by smooth muscle cells and also results in pulmonary fibrosis. The overall result is diffuse alveolar damage.
Damage to the alveolar capillary can lead to capillary leak syndrome and interstitial oedema, resulting in further damage to pneumocytes. Ongoing immune reaction results in long term chronic damage.
Interstitial Disease
Caused by Inflammation and fibrosis of alveolar walls and changes in the capillary endothelium and alveolar lining cells.
Histological changes consist of proliferation of fibroblasts and excess deposition of collagen.
Pulmonary function testing (PFTs) shows a decrease in diffusion capacity.
Obstructive Lung Disease
Results from airway narrowing which may be due to bronchospasm, mucus or luminal narrowing from oedema, inflammation or scarring.
PFTs show a decrease in expiratory airflow with a decrease in the FEV1/FVC ( Forced expiratory volume in 1 second/ Total forced vital capacity)
Restrictive Lung Disease
Due to alteration in the elasticity of the pulmonary system.
May be due to inflammation and fibrosis or growth impairment of the lung or musculo skeletal system.
Children are more susceptible to chronic respiratory damage due to impairment of normal growth and development of the lungs and thoracic cage
PFTs shows an increase in FEV1/FVC ratio with an increase maximal expiratory airflow.
With more advanced restrictive disease total lung capacity, vital capacity and lung volumes are decreased with evidence of uneven ventilation.
Pneumonitis
Acute pulmonary toxicity often presents clinically as pneumonitis.
Symptoms can include:
- non productive cough
- fever
- dyspnea
The presentation may be acute with Acute Respiratory Distress syndrome ( ARDS).
Other toxicities associated with cancer therapy can include:
- bronchospasm
- pleural effusion
- bronchiolitis obliterans
- pulmonary venous occlusion
- pneumothorax
- pulmonary hemorrhage
