Guidelines for Complications of Cancer Treatment Vol VIII Part B

Symptoms: Symptoms related to pulmonary fibrosis areproportional to the extent of the lung parenchyma involvedand the patients’ preexisting pulmonary reserves. Most patientswith radiation fibrosis are asymptomatic. Advanced cases maymanifest with chronic respiratory failure, dyspnea on effort,reduced exercise tolerance, orthopnea, cyanosis and fingerclubbing. Symptoms are generally minimal if fibrosis is limitedto less than 50% of one lung.Diagnostic modalities: Radiologic changes consistent withfibrosis are seen in most patients who have received lungirradiation even if they did not develop acute pneumonitis.Whether there is always an acute phase that precedes lungfibrosis is still unknown, though most authors believe this islikely the case. Chest x-rays have the appearance of linearstreaking, radiating from the area of previous pneumonitis.which may extend outside the irradiated region. There may beconcomitant regional contraction, pleural thickening, andtenting of the diaphragm. There may also be resultantcompensatory hyperinflation of adjacent or contralateral lungtissue. Findings of pulmonary fibrosis are usually seen 12months to 2 years after radiation. Computerized tomographyis currently favored to image diagnosis. Eventually, thepreviously irradiated lung can develop dense fibrotic nodules,especially in the area of previous tumor. Fibrosis usually resultsin mild deterioration in pulmonary function. This may resultin decreased maximum inspiratory volume and tidal volumeusually with mild to moderate increase in respiratory rate. Incase of small volume involvement, pulmonary function testsdo not demonstrate significant change, owing to the functionalcompensation of adjacent lung regions. Hence, diffusioncapacity may be the best assessment of whole organ functionbecause it is least likely to be effected by compensatorychanges in unirradiated portions of the lung.317