How would you manage a treatment interruption during SBRT to the liver?

The answer to this question is "it depends". Given that the original delivery of SBRT was two fractions per week over a period of 2.5-3 weeks for 3-5 fractions, if the patient completes SBRT within this time frame, it would still not truly qualify as a treatment interruption.

Further, if you deliver ...

The University of Michigan group has tested intentional 4-week treatment breaks after delivering 3 out of 5 planned SBRT fractions. There was no apparent reduction in local control, so I think completing the planned treatment course after such a break could be reasonable.