Fluorodeoxyglucose Positron Emission Tomography Response and Normal Tissue Regeneration After Stereotactic Body Radiotherapy to Liver Metastases

Maximum SUV decreases over the first months after SBRT to plateau at 3.1, similar to the median SUVmax of normal livers. Transient moderate increases in SUVmax may be observed after SBRT. We propose a cutoff SUVmax ≥6, twice the baseline normal liver SUVmax, to score local failure by PET criteria. Post-SBRT values between 4 and 6 would be suspicious for local tumor persistence or recurrence. The volume of normal liver reached nadir 3-6 months after SBRT and regenerated within the next 6 months.