Evaluation of the Biodistribution of [99mTc]Tc-PSMA-GCK01 SPECT/CT in a prospective, intraindividual comparison with [68Ga]PSMA-11 PET/CT for Phenotyping in mCRPC prior to PSMA-targeted radioligand therapy

Evaluation of the Biodistribution of [99mTc]Tc-PSMA-GCK01 SPECT/CT in a prospective, intraindividual comparison with [68Ga]PSMA-11 PET/CT for Phenotyping in mCRPC prior to PSMA-targeted radioligand therapy | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Evaluation of the Biodistribution of [99mTc]Tc-PSMA-GCK01 SPECT/CT in a prospective, intraindividual comparison with [68Ga]PSMA-11 PET/CT for Phenotyping in mCRPC prior to PSMA-targeted radioligand therapy Emil Novruzov, Eduards Mamlins, Joseph Kabunda, Jens Cardinale, and 17 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9196629/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Background PSMA-PET/CT became an important means for prostate cancer management. The high-resolution and signal-to-noise ratio of PET is mandatory in primary staging or biochemical relapse that often present with tiny lesions. PSMA-PET is also used to select patients for PSMA-targeted radioligand-therapy, but scanner availability increasingly becomes a bottleneck. The resolution of PSMA-SPECT/CT might be sufficient to tailor PSMA positive vs. negative disease and would help overcome supply limitations. This prospective, monocentric study evaluates the biodistribution and tumor uptake of [ 99m Tc]Tc-PSMA-GCK01 in an intra-individual head-to-head comparison with [ 68 Ga]PSMA-11 to assess its suitability for phenotyping prior to RLT. Results A cohort of ten patients (median age, 68 y; range, 56–85 y) with advanced-stage, metastatic prostate cancer underwent both unenhanced [ 68 Ga]PSMA-11 PET/CT and [ 99m Tc]Tc-PSMA-GCK01 SPECT/CT scans with a mean time interval of 6 days (± 1). The tracer uptake in malignant lesions and normal organs was assessed visually and semi-quantitatively using spherical VOIs by two nuclear medicine physicians in consensus. Compared to [ 99m Tc]Tc-PSMA-GCK01, [ 68 Ga]PSMA-11 displayed a trend toward higher uptake in normal organs. Renal tracer uptake was significantly higher with [ 68 Ga]PSMA-11 than with [ 99m Tc]Tc-PSMA-GCK01. In the salivary glands and liver, there was no statistically significant difference in uptake between the two tracers, although [ 99m Tc]Tc-PSMA-GCK01 displayed a trend toward lower uptake. Conclusion Our study demonstrates intraindividual comparability of [ 99m Tc]Tc-PSMA-GCK01 and [ 68 Ga]PSMA-11 with respect to normal-organ distribution including typical reference organs such as the liver or salivary glands. If only lesions > 2 cm are considered, [ 99m Tc]Tc-PSMA-GCK01 PSMA-SPECT is a viable, cost-effective alternative to [ 68 Ga]PSMA-11 to stratify patients toward or against PSMA-RLT. PSMA SPECT 99mTc PSMA-GCK01 phenotyping PSMA radioligand therapy biodistribution Full Text Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 20 Apr, 2026 Reviewers invited by journal 19 Apr, 2026 Editor invited by journal 27 Mar, 2026 Editor assigned by journal 25 Mar, 2026 First submitted to journal 25 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9196629","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":625765021,"identity":"4e8b006e-3ebb-485e-bfe2-fe1a00da826e","order_by":0,"name":"Emil Novruzov","email":"","orcid":"","institution":"University Hospital Dusseldorf: Universitatsklinikum Dusseldorf","correspondingAuthor":false,"prefix":"","firstName":"Emil","middleName":"","lastName":"Novruzov","suffix":""},{"id":625765022,"identity":"6283de8b-d58d-4b6c-b3f3-e3b215a78421","order_by":1,"name":"Eduards 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The high-resolution and signal-to-noise ratio of PET is mandatory in primary staging or biochemical relapse that often present with tiny lesions. PSMA-PET is also used to select patients for PSMA-targeted radioligand-therapy, but scanner availability increasingly becomes a bottleneck. The resolution of PSMA-SPECT/CT might be sufficient to tailor PSMA positive vs. negative disease and would help overcome supply limitations. This prospective, monocentric study evaluates the biodistribution and tumor uptake of [\u003csup\u003e99m\u003c/sup\u003eTc]Tc-PSMA-GCK01 in an intra-individual head-to-head comparison with [\u003csup\u003e68\u003c/sup\u003eGa]PSMA-11 to assess its suitability for phenotyping prior to RLT.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eA cohort of ten patients (median age, 68 y; range, 56\u0026ndash;85 y) with advanced-stage, metastatic prostate cancer underwent both unenhanced [\u003csup\u003e68\u003c/sup\u003eGa]PSMA-11 PET/CT and [\u003csup\u003e99m\u003c/sup\u003eTc]Tc-PSMA-GCK01 SPECT/CT scans with a mean time interval of 6 days (\u0026plusmn;\u0026thinsp;1). The tracer uptake in malignant lesions and normal organs was assessed visually and semi-quantitatively using spherical VOIs by two nuclear medicine physicians in consensus. Compared to [\u003csup\u003e99m\u003c/sup\u003eTc]Tc-PSMA-GCK01, [\u003csup\u003e68\u003c/sup\u003eGa]PSMA-11 displayed a trend toward higher uptake in normal organs. Renal tracer uptake was significantly higher with [\u003csup\u003e68\u003c/sup\u003eGa]PSMA-11 than with [\u003csup\u003e99m\u003c/sup\u003eTc]Tc-PSMA-GCK01. In the salivary glands and liver, there was no statistically significant difference in uptake between the two tracers, although [\u003csup\u003e99m\u003c/sup\u003eTc]Tc-PSMA-GCK01 displayed a trend toward lower uptake.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eOur study demonstrates intraindividual comparability of [\u003csup\u003e99m\u003c/sup\u003eTc]Tc-PSMA-GCK01 and [\u003csup\u003e68\u003c/sup\u003eGa]PSMA-11 with respect to normal-organ distribution including typical reference organs such as the liver or salivary glands. If only lesions\u0026thinsp;\u0026gt;\u0026thinsp;2 cm are considered, [\u003csup\u003e99m\u003c/sup\u003eTc]Tc-PSMA-GCK01 PSMA-SPECT is a viable, cost-effective alternative to [\u003csup\u003e68\u003c/sup\u003eGa]PSMA-11 to stratify patients toward or against PSMA-RLT.\u003c/p\u003e","manuscriptTitle":"Evaluation of the Biodistribution of [99mTc]Tc-PSMA-GCK01 SPECT/CT in a prospective, intraindividual comparison with [68Ga]PSMA-11 PET/CT for Phenotyping in mCRPC prior to PSMA-targeted radioligand therapy","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-27 15:27:12","doi":"10.21203/rs.3.rs-9196629/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2026-04-20T11:08:17+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-19T16:08:00+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"EJNMMI Research","date":"2026-03-27T10:30:08+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-26T00:36:04+00:00","index":"","fulltext":""},{"type":"submitted","content":"EJNMMI Research","date":"2026-03-25T17:24:44+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"ejnmmi-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejre","sideBox":"Learn more about [EJNMMI Research](http://ejnmmires.springeropen.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ejre/default.aspx","title":"EJNMMI Research","twitterHandle":"@officialEANM","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7fb504ef-a23b-4926-8beb-c1f102911298","owner":[],"postedDate":"April 27th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-27T15:27:18+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-27 15:27:12","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9196629","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9196629","identity":"rs-9196629","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}