# Fixed versus personalised (dosimetry-guided) dosing

Source: https://nuclide.cc/terms/fixed-versus-personalised-dosing/  
Nuclide record `fixed-versus-personalised-dosing` (Term). Data CC BY-NC 4.0, attribute "Data from Nuclide (nuclide.cc)"; commercial use needs a licence.

## TL;DR

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.

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.

## Fields

- Kind: Term
- Last checked: 2026-09-22
- Tags: dosimetry; PRRT; individualised therapy

## Sources

- Sandström M, et al. Phase II trial: efficacy and safety of individualized, dosimetry-based 177Lu-DOTATATE (ILUMINET), Eur J Nucl Med Mol Imaging 2022: https://link.springer.com/article/10.1007/s00259-022-05786-w
- Haug AR. PRRT of neuroendocrine tumors: individualized dosimetry or fixed dose scheme? EJNMMI Res 2020: https://pmc.ncbi.nlm.nih.gov/articles/PMC7158965/
- DUONEN trial: dosimetry-guided peptide receptor radionuclide therapy, Frontiers in Endocrinology 2025: https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2025.1716247/full

## Connected records

- technologies: [Peptide receptor radionuclide therapy (PRRT)](https://nuclide.cc/technologies/prrt/), [Radioligand dosimetry](https://nuclide.cc/technologies/radioligand-dosimetry/)
- drugs: [177Lu-edotreotide](https://nuclide.cc/drugs/itm-11/), [Lutetium-177 dotatate](https://nuclide.cc/drugs/lutathera/), [Lutetium-177 vipivotide tetraxetan](https://nuclide.cc/drugs/pluvicto/)
- ideas: [Dosimetry-personalised PRRT instead of four fixed cycles](https://nuclide.cc/ideas/idea-net-dosimetry-prrt/), [Total-body PET for personalised radioligand dosing](https://nuclide.cc/ideas/idea-total-body-pet-dosimetry/)
- terms: [Gray unit (Gy)](https://nuclide.cc/terms/gray-unit/)
- isotopes: [Lutetium-177](https://nuclide.cc/isotopes/lu-177/), [Yttrium-90](https://nuclide.cc/isotopes/y-90/)

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