The achievement of isoeffective bronchial mucosal dose during endobronchial brachytherapy

The use of endobronchial brachytherapy in the treatment of lung cancer is increasing due to the more widespread availability of high dose rate afterloading equipment. The complications include small airway (segmental and small lobar bronchi) fibrosis, stenosis, and obstructive complications in addition to hemorrhage. A progressive reduction in the diameter of the bronchial lumen occurs at each division of the bronchial tree. If uniform dwell times along a bronchial catheter treatment length are used, this will result in higher doses being given to the bronchial mucosa in the distal part of the treatment volume where the brachytherapy source mucosa distances are smaller, and underdosage proximally, where the source mucosa distances are larger.

The known mathematical relationships of the sequential reductions in the diameter of the bronchial lumen have been incorporated into two methods of optimization, which have been compared to uniform dwell times along a treatment length from trachea to segmental bronchus.

The resulting isodose plots are presented, and demonstrate the extent of the overdosage distally, and the underdosage proximally when using uniform dwell times, and the achievement of isoeffective mucosal doses when using differential dwell times.

This refinement in brachytherapy technique offers the potential for reduced normal tissue complications and possibly improved tumor control by reducing overdosage and underdosage, respectively.