3D-CRT
Prospective evaluation of early lung toxicity following three-dimensional conformal radiation therapy in non–small-cell lung cancer: preliminary results1,

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Abstract

Purpose: Radiation pneumonitis is the restricting complication following lung cancer irradiation. The correlation between dose–volume histograms (DVHs) and pneumonitis, with a clinical, radiological, and respiratory function evaluation was assessed. Special endpoint was the evaluation of respiratory function after three-dimensional conformal radiotherapy (3D-CRT).

Methods and Materials: Fifty-four patients with non metastatic non–small-cell lung cancer (NSCLC) were treated with a curative intent with 3D-CRT (66 Gy). Thirty-one patients were treated postoperatively (pneumonectomy in 9 patients) for residual tumor or massive nodal involvement (N2 or N3); 23 patients were treated with exclusive radiotherapy. Clinical evaluation, CT scan, and pulmonary functional tests were performed before and 6 weeks after irradiation. The DVHs were calculated applying lung density heterogeneity.

Results: Twenty patients had radiation pneumonitis. Irradiation significantly decreased total lung capacity. Volume of the PTV2 (more than 200 cm3) was a significant prognostic factor for lung complication.

Conclusion: DVHs combined with initial pulmonary functional tests can predict pulmonary toxicity and could allow us to adjust volume that received total highest dose with acceptable toxicity.

Introduction

The prognosis of non–small-cell lung cancer (NSCLC) remains poor because of inadequate control at the primary site after radiation therapy. Local control achievement is a requirement for survival benefits 1, 2. High dose of thoracic irradiation is associated with an improvement of local control when using either classical fractionation 3, 4, 5 or using hyperfractionated accelerated radiotherapy 6, 7, 8, 9, 10.

The tolerance of the normal lung tissue limits the dose that can be delivered, and radiation pneumonitis is the restricting complication following lung cancer irradiation. Radiation pneumonitis after thoracic irradiation has been reported in several series, even with conformal radiotherapy 11, 12, 13, 14, 15.

The relationship between the dose–volume histogram (DVHs) and the occurrence of pneumonitis improves knowledge of radiotherapy toxicity 16, 17, 18, 19. Three-dimensional conformal radiotherapy (3D-CRT) permits an improvement in tailoring target volume and minimizing normal lung irradiation. This should allow the delivery of higher doses without increasing the complication rates 20, 21.

The aim of this study was a prospective evaluation of pulmonary toxicity following 3D-CRT. The predictive value of DVHs in pneumonitis occurrence was investigated. An analysis of functional changes after pulmonary irradiation has been performed. The relation between DVHs and the reduction of lung function parameters has been analyzed.

Section snippets

Methods and materials

Between November 1996 and February 1999, 54 patients with histologically proven nonmetastatic NSCLC were included in a prospective study to evaluate the pulmonary toxicity after 3D-CRT.

Results

The volume of PTV1 and PTV2 for the 54 patients, for the 9 pneumonectomy patients, and for the 45 patients without pneumonectomy are presented in Table 1. The volumes of PTV1 and PTV2 were smaller for pneumonectomy patients, when compared with other patients.

Twenty cases of radiation pneumonitis more than or equal to Grade 2 according to the Lent–Soma scale were observed (Table 2). Eleven patients had Grade 2 pneumonitis and 9 patients had Grade 3 pneumonitis. Sixteen patients among these 20

Discussion

The influence of heterogeneity on dose calculation has been studied 1, 15. Graham et al. (1) compared dose delivered to PTV1 and to PTV2 with and without heterogeneity dose calculation. In PTV2, an underdosage of 5% or less was observed in 55% of patients and an overdosage of 10% in 29% of patients when heterogeneities were not taken into account. Martel et al. (15) decided to use heterogeneity corrected calculations, after analyzing the influence of heterogeneity corrected calculations. In our

References (26)

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Grants: PHRC no. 2701; Ligue contre le Cancer de l’Ain, Aide Recherche 1996–1997; Ligue contre le Cancer du Rhône, Aide Recherche 1996–1997.

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Acknowledgments—The authors acknowledge Mr. Toms for valuable help with English, and Michel Drevon for statistical analysis help.

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