Analysis of the influence of elective nodal irradiation on postirradiation pulmonary function.

Irradiation (RT) field selection for bronchogenic carcinoma is based on such factors as extent of disease, pulmonary function, and the perceived need for elective nodal irradiation (ENI). A technique of superimposing a patient's RT treatment film onto his quantitative perfusion lung scan can predict the fractional volume of perfused lung receiving RT and has been shown to reliably estimate the minimum post-RT pulmonary function as measured by the forced expiratory volume in one second (FEV1). This technique has been applied to 20 patients with nonresected clinically staged T1-4N0M0 lesions to quantify the pulmonary impact of varying degrees of ENI. The five treatment volumes selected were as follows: (1) tumor volume plus a 2-cm margin; (2) volume 1 plus ipsilateral hilum; (3) volume 2 plus mediastinum; (4) volume 3 plus supraclavicular fossae; and (5) volume 4 plus contralateral hilum. The median pre-RT FEV1 was 2.0 l, and the median predicted minimal post-RT FEV1 for each proposed field was field 1, 1.7 l; field 2, 1.5 l; field 3, 1.3 l; field 4, 1.1.; and field 5, 1.0 l. The decline in median predicted FEV1 with each increase in field size ranged from 2% to 12%, with a broad range of declines for each field. Such quantification can aid in decisions regarding ENI for patients with impaired pulmonary function.