# Dosimetry-personalised PRRT instead of four fixed cycles

Source: https://nuclide.cc/ideas/idea-net-dosimetry-prrt/  
Nuclide record `idea-net-dosimetry-prrt` (Idea). Data CC BY-NC 4.0, attribute "Data from Nuclide (nuclide.cc)"; commercial use needs a licence.

## TL;DR

Measure the radiation each patient's tumour and kidneys actually absorb and adjust the number and size of doses, instead of giving everyone four identical cycles.

## Summary

The idea is to personalise peptide receptor radionuclide therapy with lutetium-177 dotatate or 177Lu-edotreotide by measuring the radiation each patient's tumour, kidneys and marrow actually absorb on SPECT/CT after each cycle, and adjusting the number and size of doses. The standard of 7.4 GBq for four cycles leaves many patients under-dosed relative to renal and marrow limits, uptake varies widely, and retrospective dosimetry shows tumour absorbed dose correlates with response. The hypothesis is that dosimetry-guided PRRT raises cumulative tumour dose and response rate without exceeding organ limits. The test is a randomised phase 2 of individualised versus fixed activity; P-PRRT in Canada is already testing this, and the idea addresses the wrong-doses bottleneck.

## Fields

- Kind: Idea
- Last checked: 2026-09-07
- Hypothesis: Dosimetry-guided PRRT increases cumulative tumour dose and response rate without exceeding renal/marrow limits, versus fixed dosing.
- Rationale: Wide inter-patient variation in uptake; SPECT/CT after each cycle makes dosimetry feasible.
- Proposed test: Randomised phase 2 of individualised vs fixed activity with ORR and PFS endpoints.
- Maturity: early-clinical

## Sources

- ClinicalTrials.gov NCT03049189: COMPETE: https://clinicaltrials.gov/study/NCT03049189

## Connected records

- isotopes: [Lutetium-177](https://nuclide.cc/isotopes/lu-177/)
- indications: [Grade 3 well-differentiated neuroendocrine tumour](https://nuclide.cc/indications/grade-3-net/), [Neuroendocrine tumours](https://nuclide.cc/indications/neuroendocrine/), [Pancreatic neuroendocrine tumours](https://nuclide.cc/indications/pancreatic-net/), [Small intestinal neuroendocrine tumours](https://nuclide.cc/indications/small-intestinal-net/)
- technologies: [Peptide receptor radionuclide therapy (PRRT)](https://nuclide.cc/technologies/prrt/), [SPECT & bone scan](https://nuclide.cc/technologies/spect/)
- drugs: [177Lu-edotreotide](https://nuclide.cc/drugs/itm-11/), [Lutetium-177 dotatate](https://nuclide.cc/drugs/lutathera/)
- terms: [Dosimetry](https://nuclide.cc/terms/dosimetry/), [Fixed versus personalised (dosimetry-guided) dosing](https://nuclide.cc/terms/fixed-versus-personalised-dosing/)
- bottlenecks: [Dosimetry standardisation for radioligand therapy](https://nuclide.cc/bottlenecks/b-dosimetry-standardisation/), [Wrong doses](https://nuclide.cc/bottlenecks/b-dose-optimisation/)
- ideas: [Kidney-dosimetry-guided dosing as the default for PSMA radioligand therapy](https://nuclide.cc/ideas/idea-dosimetry-guided-dosing-standard/)
- roadmaps: [Dosimetry roadmap: MIRD schema → fixed dosing → personalised, image-based dose](https://nuclide.cc/roadmaps/dosimetry-roadmap/)

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