{"entity":{"id":"idea-dosimetry-guided-dosing-standard","kind":"idea","name":"Kidney-dosimetry-guided dosing as the default for PSMA radioligand therapy","aka":[],"tldr":"Right now, most patients get the same number of treatment cycles at the same radioactive dose regardless of their own biology. Measuring how much radiation actually reaches each patient's kidneys after the first dose could let doctors safely give some patients more cycles and stop earlier in others, rather than using one fixed schedule for everyone.","summary":"The label dosing for lutetium-177 vipivotide tetraxetan (Pluvicto) is a fixed 7.4 GBq every six weeks for up to six cycles, as tested in the VISION trial, regardless of how much radiation an individual patient's kidneys, salivary glands or tumours actually receive. Dosimetry studies show this fixed approach leaves dose headroom in many patients: a single-institution series at the University of Wisconsin found that among 19 patients with post-cycle-one voxel-level SPECT/CT dosimetry, kidney and salivary gland absorbed doses tracked the VISION phase 3 benchmarks, and 15 of 19 patients could have safely received a seventh cycle and 18 of 19 an additional cycle based on a 24 Gy kidney and 20 Gy salivary gland threshold, while a smaller number needed early discontinuation or dose delay. In neuroendocrine tumour PRRT, the LUMEN and LUTADOSE studies found that tumour-absorbed dose measured after the first cycle predicts progression-free survival, reinforcing that a fixed four- or six-cycle schedule is a population average rather than a patient-specific optimum.\n\nSeveral trials are now testing personalised dosing directly rather than relying on retrospective series. FLEX-MRT (NCT06216249, UCLA, randomised phase 2, about 90 patients) compares a flexible, SPECT/CT-response-guided schedule of up to 12 cycles with treatment holidays against the standard fixed six-cycle regimen, with 2-year survival as the primary endpoint. PRODIGY-2 (NCT06943495, CHU de Québec) is testing whether renal-dosimetry-guided activity escalation is feasible and safe compared with the fixed-activity regimen. In neuroendocrine tumours, DOBATOC (NCT04917484) is a randomised phase 2 testing kidney-dose-governed individualised dosing (targeting a 24 Gy cumulative kidney dose) against fixed dosing, with progression-free survival as the primary outcome.\n\nThis proposal is deliberately broader than the existing dosimetry-personalised-PRRT idea already in this graph, which is specific to neuroendocrine tumours: the claim here is that dosimetry-guided dosing should become the default approach across radioligand therapies generally, including PSMA-targeted treatment, not just PRRT.","asOf":"2026-09-22","links":[{"label":"FLEX-MRT: Phase 2 Randomized Trial of Flexible Dosing Schedule of 177Lu-PSMA-617 (ClinicalTrials.gov, NCT06216249)","url":"https://clinicaltrials.gov/study/NCT06216249"},{"label":"PRODIGY-2: Personalized vs. Fixed-Activity 177Lu-PSMA-617 (ClinicalTrials.gov, NCT06943495)","url":"https://clinicaltrials.gov/study/NCT06943495"},{"label":"Personalized Dosimetry Guides 177Lu-PSMA-617 Therapy (conference coverage, University of Wisconsin series)","url":"https://www.hmpgloballearningnetwork.com/site/rpei/conference-coverage/personalized-dosimetry-guides-177lu-psma-617-therapy-prostate-cancer"},{"label":"Radioligand therapy and tumor dosimetry: where are we and where are we going? (2026 review)","url":"https://link.springer.com/article/10.1007/s40336-026-00769-5"},{"label":"VISION: 177Lu-PSMA-617 (ClinicalTrials.gov, NCT03511664)","url":"https://clinicaltrials.gov/study/NCT03511664"}],"tags":["dosimetry","personalised dosing","prostate"],"related":["idea-net-dosimetry-prrt","radioligand-dosimetry","pluvicto","vision","lu-177"],"indications":[],"sections":[],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"hypothesis":"Replacing lutetium-177-PSMA-617's fixed six-cycle, fixed-activity regimen with a kidney-dosimetry-guided number of cycles and activity will let more patients safely receive additional beneficial cycles, and will identify others who should stop earlier, without exceeding organ-radiation-dose limits.","rationale":"A retrospective series of 19 patients found organ doses consistent with VISION trial benchmarks and identified that the great majority could have safely received extra cycles based on kidney and salivary gland dose thresholds. In neuroendocrine PRRT, the LUMEN and LUTADOSE studies independently found that cycle-one tumour-absorbed dose predicts progression-free survival, supporting the general principle that a fixed schedule under- or over-treats many patients. Multiple randomised trials (FLEX-MRT, PRODIGY-2, DOBATOC) are now directly testing personalised, dosimetry-guided dosing against fixed dosing; none has yet reported a mature result.","test":"FLEX-MRT (NCT06216249), an already-enrolling randomised phase 2 trial (approximately 90 patients) comparing a SPECT/CT-response-guided flexible dosing schedule of up to 12 cycles, including treatment holidays, against the standard fixed six-cycle regimen of 177Lu-PSMA-617, with 2-year survival as the primary endpoint; DOBATOC (NCT04917484) provides the analogous randomised test in neuroendocrine PRRT.","maturity":"being-tested-at-scale","actor":"research","cost":"medium","horizonYears":5},"route":"/ideas/idea-dosimetry-guided-dosing-standard/","neighbours":{"idea":[{"id":"idea-net-dosimetry-prrt","kind":"idea","name":"Dosimetry-personalised PRRT instead of four fixed cycles","route":"/ideas/idea-net-dosimetry-prrt/"}],"technology":[{"id":"radioligand-dosimetry","kind":"technology","name":"Radioligand dosimetry","route":"/technologies/radioligand-dosimetry/"}],"drug":[{"id":"pluvicto","kind":"drug","name":"Lutetium-177 vipivotide tetraxetan","route":"/drugs/pluvicto/"}],"trial":[{"id":"vision","kind":"trial","name":"VISION","route":"/trials/vision/"}],"isotope":[{"id":"lu-177","kind":"isotope","name":"Lutetium-177","route":"/isotopes/lu-177/"}]}}