Inhomogeneity correction in radiotherapy for lung cancer in multicenter clinical trials.

Purpose: Dose distribution in patients in past multicenter clinical trials was reviewed from the perspective of clinicians to evaluate the quality of treatment and to improve the quality of future clinical trials.

Materials And Methods: Thirty patients with stage III lung cancer, who had undergone radical radiation therapy in multicenter clinical trials were retrospectively reviewed. A two-dimensional treatment planning system using Clarkson integration was used to calculate correction factors at the primary lesions and at the mediastinal lymph nodes.

Results: Correction factors at the primary lesions ranged from 1.00 to 1.12 (mean, 1.06) and from 1.02 to 1.14 (mean, 1.06) in the AP/PA fields and in the oblique fields, respectively. The lowest values of correction factors at the mediastinal lymph nodes on the axial plane including the primary lesions ranged from 0.93 to 1.04 (mean, 0.98) and from 0.97 to 1.10 (mean, 1.02) in the AP/PA fields and in the oblique fields, respectively. In 14 patients whose primary tumor was located in the upper lung field, the correction factors at the subcarinal lymph nodes ranged from 0.90 to 1.01 (mean, 0.96) in the AP/PA fields.

Conclusion: Delivered doses lower than those prescribed at the mediastinal lymph nodes should be taken into consideration to improve the quality of multicenter clinical trials.