What dose-fractionation scheme and esophageal constraints should be used to treat an ultra-central, medically inoperable, stage I NSCLC abutting the esophagus?  

For lesions abutting the esophagus, SBRT with BED >100 Gy should NOT be used due to high risk for ulceration and even fistula. Instead of SBRT, more fractionated radiotherapy with BED <84 Gy should be considered (60 Gy in 15 FX is still too high for the esophagus). In addition to maximal point...

I prefer to prescribe 60/15 to the PTV with no more than 45/15 to the esophagus. Gated treatment targeting the GTV (instead of free-breathing targeting the iGTV) is strongly preferred for cases like this.