# Dosimetry-personalised PRRT instead of four fixed cycles

Source: https://onco.cc/ideas/idea-net-dosimetry-prrt/  
OnCo record `idea-net-dosimetry-prrt` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.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

- cancers: [Grade 3 well-differentiated neuroendocrine tumour](https://onco.cc/cancers/grade-3-net/), [Neuroendocrine tumours](https://onco.cc/cancers/neuroendocrine/), [Pancreatic neuroendocrine tumours](https://onco.cc/cancers/pancreatic-net/), [Small intestinal neuroendocrine tumours](https://onco.cc/cancers/small-intestinal-net/)
- technologies: [Peptide receptor radionuclide therapy (PRRT)](https://onco.cc/technologies/prrt/), [SPECT & bone scan](https://onco.cc/technologies/spect/)
- drugs: [177Lu-edotreotide](https://onco.cc/drugs/itm-11/), [Lutetium-177 dotatate](https://onco.cc/drugs/lutathera/)
- terms: [Dosimetry](https://onco.cc/terms/dosimetry/)
- trials: [COMPETE](https://onco.cc/trials/compete/), [Lutetium 177Lu-Edotreotide Versus Best Standard of Care in Well-differentiated Aggressive Grade-2 and Grade-3 GastroEnteroPancreatic NeuroEndocrine Tumors (GEP-NETs) - COMPOSE](https://onco.cc/trials/nct04919226/), [NETTER-1](https://onco.cc/trials/netter-1/), [Study to Evaluate the Efficacy and Safety of Lutathera in Patients With Grade 2 and Grade 3 Advanced GEP-NET](https://onco.cc/trials/nct03972488/)
- key papers: [Lutetium-177 DOTATATE: A Practical Review](https://onco.cc/key-papers/paper-lutetium-177-dotatate-neuroendocrine-pract-radiat-oncol-2022/)
- bottlenecks: [Wrong doses](https://onco.cc/bottlenecks/b-dose-optimisation/)

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