Formal discussant Thomas J. Dilling, MD, MS, of Moffitt Cancer Center, Tampa, Florida, congratulated the authors on this study.

He noted that early findings from both treatment arms showed similar rates of grade 3 and higher toxicity. “However, in the [four-fraction] arm, a fatal event occurred in a patient with undiagnosed interstitial lung disease. This brings home the point that patients with pulmonary fibrosis probably should not be treated with SBRT [stereotactic body radiotherapy], and if they are, perhaps only for a single lesion.”

Thomas J. Dilling, MD, MS

He questioned whether the optimal dose for SBRT to the lung was used in SAFRON II, noting that many institutions are trying to define the optimal dose. “I question whether the biologic effective dose of 105 or 106 Gy used in this trial is effective for the control of lung metastasis. I fear it might not be. It is important as a field to try to quantitate relative radiosensitivity of the different doses, and it is not clear that the dose used in the trial is sufficient.”

“The tumor control data from this trial are pending, and the [SBRT] dose may be too low to control metastatic disease. However, time will tell,” Dr. Dilling stated. 

DISCLOSURE: Dr. Dilling has served as a consultant or advisor to AstraZeneca.