{"entity":{"id":"fixed-versus-personalised-dosing","kind":"term","name":"Fixed versus personalised (dosimetry-guided) dosing","aka":[],"tldr":"Most radioactive cancer treatments today give every patient the same amount, on the same schedule, regardless of body size. Researchers are testing whether measuring how much radiation reaches a patient's kidneys and tumours, and adjusting the dose accordingly, works better and is safer.","summary":"Approved peptide receptor radionuclide therapy (lutetium-177 dotatate, Lutathera) and PSMA radioligand therapy (lutetium-177 vipivotide tetraxetan, Pluvicto) are both dosed as a fixed activity per cycle regardless of patient size: Lutathera as 7.4 GBq every 8 weeks for four cycles, the schedule used in NETTER-1, and Pluvicto similarly as a fixed per-cycle activity. This mirrors how most targeted small-molecule cancer drugs are dosed, but it ignores patient-to-patient variability in biodistribution, renal clearance and tumour burden, all of which change how much radiation different organs and tumours actually absorb from the same injected activity.\n\nDosimetry-guided (personalised) dosing instead measures absorbed dose to organs at risk (chiefly kidney and bone marrow) after each cycle, using post-therapy SPECT/CT or serial blood and imaging sampling, and adjusts the number of cycles or the activity of subsequent cycles to reach a pre-defined cumulative dose limit (commonly around 23 Gy to the kidney and roughly 2 Gy to bone marrow, thresholds extrapolated from external-beam radiotherapy experience). A single-centre Swedish phase 2 trial individualising the number of 177Lu-DOTATATE cycles by renal biological effective dose reported a 16% partial response rate, 66% stable disease, and a median progression-free survival of 29 months and overall survival of 47 months in 96 evaluable patients, comparable to or exceeding NETTER-1 in a similar population. The ongoing DUONEN phase 3 trial in Poland is comparing fixed 7.4 GBq dosing against several dosimetry-guided 177Lu/90Y regimens with per-cycle activity adjusted to organ dose.\n\nNo randomised trial has yet shown personalised dosing to be superior to the fixed NETTER-1/VISION schedules on a hard efficacy endpoint, and the nuclear medicine community has not agreed a single validated dosimetry methodology, which is why fixed dosing remains the regulatory-approved standard of care. The idea that dosimetry-personalised PRRT could replace four fixed cycles is an active research question rather than settled practice.","asOf":"2026-09-22","links":[{"label":"Sandström M, et al. Phase II trial: efficacy and safety of individualized, dosimetry-based 177Lu-DOTATATE (ILUMINET), Eur J Nucl Med Mol Imaging 2022","url":"https://link.springer.com/article/10.1007/s00259-022-05786-w"},{"label":"Haug AR. PRRT of neuroendocrine tumors: individualized dosimetry or fixed dose scheme? EJNMMI Res 2020","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC7158965/"},{"label":"DUONEN trial: dosimetry-guided peptide receptor radionuclide therapy, Frontiers in Endocrinology 2025","url":"https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2025.1716247/full"}],"tags":["dosimetry","PRRT","individualised therapy"],"related":["radioligand-dosimetry","prrt","itm-11","lutathera","pluvicto","idea-net-dosimetry-prrt","idea-total-body-pet-dosimetry","gray-unit","lu-177","y-90"],"indications":[],"sections":[],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"category":"therapy"},"route":"/terms/fixed-versus-personalised-dosing/","neighbours":{"technology":[{"id":"prrt","kind":"technology","name":"Peptide receptor radionuclide therapy (PRRT)","route":"/technologies/prrt/"},{"id":"radioligand-dosimetry","kind":"technology","name":"Radioligand dosimetry","route":"/technologies/radioligand-dosimetry/"}],"drug":[{"id":"itm-11","kind":"drug","name":"177Lu-edotreotide","route":"/drugs/itm-11/"},{"id":"lutathera","kind":"drug","name":"Lutetium-177 dotatate","route":"/drugs/lutathera/"},{"id":"pluvicto","kind":"drug","name":"Lutetium-177 vipivotide tetraxetan","route":"/drugs/pluvicto/"}],"idea":[{"id":"idea-net-dosimetry-prrt","kind":"idea","name":"Dosimetry-personalised PRRT instead of four fixed cycles","route":"/ideas/idea-net-dosimetry-prrt/"},{"id":"idea-total-body-pet-dosimetry","kind":"idea","name":"Total-body PET for personalised radioligand dosing","route":"/ideas/idea-total-body-pet-dosimetry/"}],"term":[{"id":"gray-unit","kind":"term","name":"Gray unit (Gy)","route":"/terms/gray-unit/"}],"isotope":[{"id":"lu-177","kind":"isotope","name":"Lutetium-177","route":"/isotopes/lu-177/"},{"id":"y-90","kind":"isotope","name":"Yttrium-90","route":"/isotopes/y-90/"}]}}