Abstract Background The BULLSEYE trial is a multicenter, open-label, randomized controlled trial to test the hypothesis if 177 Lu-PSMA is an effective treatment in oligometastatic hormone-sensitive prostate cancer (oHSPC) to prolong the progression-free survival (PFS) and postpone the need for androgen deprivation therapy (ADT). The original study protocol was published in 2020. Here, we report amendments that have been made to the study protocol since the commencement of the trial. Changes in methods and materials Two important changes were made to the original protocol: (1) the study will now use 177 Lu-PSMA-617 instead of 177 Lu-PSMA-I&T and (2) responding patients with residual disease on 18 F-PSMA PET after the first two cycles are eligible to receive additional two cycles of 7.4 GBq 177 Lu-PSMA in weeks 12 and 18, summing up to a maximum of 4 cycles if indicated. Therefore, patients receiving 177 Lu-PSMA-617 will also receive an interim 18 F-PSMA PET scan in week 4 after cycle 2. The title of this study was modified to; “Lutetium-177-PSMA in Oligo-metastatic Hormone Sensitive Prostate Cancer” and is now partly supported by Advanced Accelerator Applications, a Novartis Company. Conclusions We present an update of the original study protocol prior to the completion of the study. Treatment arm patients that were included and received 177 Lu-PSMA-I&T under the previous protocol will be replaced. Trial registration ClinicalTrials.gov NCT04443062 . First posted: June 23, 2020.