Fixed versus personalised (dosimetry-guided) dosing
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.
Overview
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.
Dosimetry-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.
No 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.
Similar pages
not linked directly; found by shared links- TermRenal protection with amino acid co-infusion
Shares Gray unit (Gy), 177Lu-edotreotide, Yttrium-90, Peptide receptor radionuclide therapy (PRRT) and the tag PRRT.
- Key paperEANM dosimetry committee recommendations for dosimetry of 177Lu-labelled somatostatin-receptor- and PSMA-targeting ligands
Shares Gray unit (Gy), Radioligand dosimetry, Peptide receptor radionuclide therapy (PRRT), Lutetium-177 vipivotide tetraxetan and the tag dosimetry.
- TechnologySPECT dosimetry workflow for radionuclide therapy
Shares Radioligand dosimetry, Yttrium-90, Peptide receptor radionuclide therapy (PRRT), Lutetium-177 and the tags dosimetry, PRRT.
- BottleneckDosimetry standardisation for radioligand therapy
Shares Dosimetry-personalised PRRT instead of four fixed cycles, Total-body PET for personalised radioligand dosing, Radioligand dosimetry, Peptide receptor radionuclide therapy (PRRT) and the tag dosimetry.
- IdeaKidney-dosimetry-guided dosing as the default for PSMA radioligand therapy
Shares Dosimetry-personalised PRRT instead of four fixed cycles, Radioligand dosimetry, Lutetium-177 vipivotide tetraxetan, Lutetium-177 and the tag dosimetry.
- RoadmapDosimetry roadmap: MIRD schema → fixed dosing → personalised, image-based dose
Shares Gray unit (Gy), Dosimetry-personalised PRRT instead of four fixed cycles, Total-body PET for personalised radioligand dosing, Radioligand dosimetry.
- Key paperResults and adverse events of personalised peptide receptor radionuclide therapy in 1048 patients with neuroendocrine neoplasms
Shares Radioligand dosimetry, Yttrium-90, Peptide receptor radionuclide therapy (PRRT), Lutetium-177 dotatate and the tag PRRT.
- PersonErik S. Mittra
Shares Yttrium-90, Peptide receptor radionuclide therapy (PRRT), Lutetium-177 dotatate, Lutetium-177 and the tag PRRT.