ESR1 and breast cancer: In a very thorough study with 312 18F-FES-PET scans in 239 patients with documented ER positive primary breast cancer, Peterson et al. [30] demonstrated that 18F-FES imaging protocols may be simplified without sacrificing the validity of the results, as calculation of 18F-FES SUV should be sufficient to assess tracer uptake for the purpose of inferring ER expression.