 As extension of above, a very real ongoing challenge that the investigators have evaluated within clinical practice is that current guidelines defining the high risk patient are subjective and prone to physician bias. A recent secondary analysis of clinical trial inclusion criteria for SBRT underscored this bias by demonstrating that many patients that were considered inoperable were perhaps reasonable surgical candidates. Based on standard pulmonary function tests the inoperable SBRT patients had a diffusion capacity 33 higher than the high risk surgical patients in ACOSOG Z4032. Conversely, stratification of high risk surgical patients within ACOSOG Z4032 trial identified an extremely high risk subset median DLCO 30, FEV1 39 with a 90-day 3 adverse event rate of 48 compared to the lowest risk subset DLCO 69, FEV1 56 with a 90-day 3 adverse event rate of only 24. In the absence of a clinical trial or a prospective database, there is currently no objective algorithm to guide the assignment of surgery versus SBRT. 