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Small Lung Size Increases the Risk of Radiation Pneumonitis in Lung Cancer Patients

T Briere

TM Briere*, SL Tucker, Z Liao, MK Martel, UT MD Anderson Cancer Center, Houston, TX

TU-G-108-3 Tuesday 4:30PM - 6:00PM Room: 108

Purpose: There may be certain populations of lung cancer patients who are especially sensitive to radiation pneumonitis. We have examined the relationship of lung size with the risk of pneumonitis.

Methods: A total of 509 non-small cell carcinoma patients were included in this study. Patients received normally fractionated radiation (180 - 225 cGy per fraction) with a minimum total dose of 50 Gy. Patients were planned with either 3D conformal (296 pts) or intensity modulated radiation therapy (IMRT, 213 pts). Radiation pneumonitis was graded by the treating physician according to the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) 3.0. Univariate analysis was performed considering mean lung dose, percentage DVH, lung size, and spared lung. The Lyman-Kutcher-Burman (LKB) method was used to fit the normal tissue complication probability (NTCP) curve to the data with respect to effective dose.

Results: Overall 20% of patients developed Grade 3 or higher pneumonitis, including 24% of the 3D patients and 15% of the IMRT patients. Univariate analysis showed lung size, mean lung dose, percentage treated and spared lung volumes to be significant. An LKB fit to the effective dose showed that it is important to take the volume parameter into account. The risk of pneumonitis predicted by NTCP analysis is underestimated for patients with small total lung sizes (< 2550 cc), where 40% of patients developed Grade 3 or higher pneumonitis.

Conclusion: Patients with small lung sizes may be especially vulnerable to radiation pneumonitis. This new finding could be used during treatment planning to reduce the risk of pneumonitis in patients with small lungs.

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