- Tumor(s) must be in a location/configuration such that risk of fistula is considered relatively low; this means that there can be no evidence of tumor invasion of a major (lobar/hilar) pulmonary vessel(s), aorta, vena cava, trachea or mainstem bronchus or esophagus; additional studies may be needed to assess this, including CT angiogram, MRI, bronchoscopy, esophagoscopy