Long-Term Changes in Pulmonary Function Tests Following Definitive Radiotherapy for Lung Cancer

Reviewer: Ryan Smith, MD
OncoLink
Last Modified: October 9, 2002

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Presenter: Keith Miller
Presenter's Affiliation: Duke University
Type of Session: Scientific

Background

    The majority of patients with lung cancer present in an inoperable stage and hence require radiation therapy. Thoracic radiation can affect Pulmonary Function Tests (PFT) and cause clinical pneumonitis. Prior studies have had either very short term follow up or were reported in patients who received radiation for lymphoma or breast cancer. This abstract reports pneumonitis symptoms and changes in PFT's with long-term follow up in patients who received radiation therapy for treatment of lung cancer.

Materials and Methods

  • Out of 128 patients with lung cancer treated with definitive radiation therapy, 13 patients had PFT follow up of greater than 2 years without other disease recurrence.
  • Median radiation dose was 71.4 Gy
  • Mean pretreatment PFTs were: FEV1-67%, FVC-72%, DLCO 70%
  • Patients were evaluated with respect to % change in predicted PFTs, changes relative to baseline, and clinical symptoms
  • No patient smoked following treatment

Results

  • There was a downward trend of PFT values following radiation therapy: FEV1 decreased an average of 7%/yr, FVC decreased 9.5%/year, and DLCO decreased 3.5%/year with follow up ranging from 3-8 years.
  • 3 patients had no pulmonary symptoms after radiation therapy. Two patients had a mild cough that required no intervention, and 8 patients experienced some dyspnea, which was progressive in 7/8 patients. However, only 1 patient had Grade 3 dyspnea.

Author's Conclusions

  • There was a continued decline in PFT's beyond 1 year following thoracic radiation therapy
  • This denoted progressive lung injury by unknown mechanisms
  • "Late" onset (>21 months after treatment) changes commonly occurred

Clinical/Scientific Implications

    This study demonstrates the progressive nature of lung damage caused by thoracic radiation therapy. Although the amount of decrease in PFTs is higher and more drawn out than previously reported, figures are presented here for patients with lung cancer (with likely more advanced disease state, lower overall performance status, and compromised normal lung tissue from years of smoking) treated with high doses of radiation. These factors almost certainly contribute to these more significant changes in PFTs. However, with this few patients with variable changes, definitive conclusions cannot be made. Even with these limitations, though, it does speak to the fact that there definitely is a dose-volume relationship with radiation treatment to the lung. Also, although these decreases were still relatively mild and very few patients developed significant symptoms, in should be noted that these decreases are in patients in which their baseline lung function are likely already compromised. Therefore, any additional decrements could affect patients' overall quality of life. This should be noted when designing radiation fields and when deciding on total doses to the thorax.

Oncolink's ASTRO Coverage made possible by an unrestricted Educational Grant from Ortho Biotech.


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