Recommendations for the dosimetry of patients undergoing therapy with radiopharmaceuticals that include 177Lu.

Currently the two radiopharmaceuticals approved by the AEMPS that include 177Lu are [177Lu]Lu-DOTA-TATE for the treatment of neuroendocrine tumours and [177Lu]Lu-PSMA-617 for the treatment of mCRPC. The RD601/2019 states that for all medical exposure of patients for radiotherapeutic purposes, exposures of target volumes shall be individually planned and their delivery appropriately verified taking into account that doses to non-target volumes and tissues shall be as low as reasonably achievable and consistent with the intended radiotherapeutic purpose of the exposure. However, for both radiopharmaceuticals the treatment is performed by administering cycles of 7.4 GBq of the radiopharmaceutical - 4 cycles for [177Lu]Lu-DOTA-TATE and 6 cycles for [177Lu]Lu-PSMA-617. This implies that treatments are not planned in advance, but can at least be verified by dosimetry. The purpose of the present document is to provide recommendations for the dosimetry of patients in treatments with the aforementioned radiopharmaceuticals.