Factors influencing target confirmation in three dimensional conformal radiotherapy for lung cancer / 中华放射肿瘤学杂志

ABSTRACT

Objective To reasonably confirm the target of 3-dimensional conformal radiation therapy (3DCRT) for lung cancer. Methods While a patient was breathing, the motion of the primary lesion in the lung was observed by fluoroscopy. The extent of motion of the primary lesion during irradiation was evaluated by portal films. Three 3DCRT plannings for lung cancer, in which gross tumor volume (GTV) decided by a group of radiation oncologists and implemented, were taken as the standard. The GTV delineated by five radiation oncologits was compared with the standard by computing the radial line measurement variation (RLMV). Results From fluoroscopic observation in fifty-nine patients, the extent of lesion motion was the largest in cephalo-caudal direction, with 14.3 mm for lesions in the lower and 7.1 mm (median) for middle part of the lung. In lateral and antero-posterior directions, it was within 4. 0 mm. The motion error during irradiation was 4. 2 mm in lateral direction and 4.6 mm in cephalo-caudal direction. The random error, system error and total error for set-up uncertainty were 3.4 mm, 6.0 mm, and 6.9 mm. Compared to the standard, the discrepancy of GTV could be as large as 150% . The largest RLMV was observed in the area of lung hilar nodes. Conclusions The target of 3-dimensional conformal radiation therapy for lung cancer should be confirmed individually and delineated by a group of radiation oncologists. A more efficient fixing device is needed owing to the large total error for set-up.