Introduction Semi-quantitative uptake measurements are part of the PROMISE framework for PET/CT interpretation of tracers targeting the prostate-specific membrane antigen (PSMA), where tumor uptake is compared to uptake in reference tissues. [18F]PSMA-1007 has primarily hepatobiliary excretion and it is suggested to use spleen as reference tissue instead of liver. The aim of this study is to investigate the normal range and interpatient variability of [18F]PSMA-1007 uptake in reference tissue for prostate cancer patients, with particular focus on the splenic uptake. Materials and methods A total of 102 [18F]PSMA-1007 PET/CT scans of prostate cancer patients with biochemical recurrence (BCR) from three hospitals were included in the analysis. SUVmax and SUVmean measurements were performed in the blood pool, liver, spleen, and parotid glands. Results are reported as median with percentiles [5th, 95th]. Results For 15/102 (15%) and 20/102 (20%) of the patients, the SUVmax and SUVmean, respectively, were higher in the spleen than in the parotid glands. Median SUVmax of the reference tissues were 1.2 [0.6, 2.2] for blood, 15.8 [8.9, 26.2] for spleen, and 26.6 [14.5, 40.4] for the parotid glands. Median SUVmean were 11.9 [6.6, 20.7] for spleen and 19.3 [11.2, 32.1] for the parotid glands. Conclusion In this multicenter cohort of BCR patients, [18F]PSMA-1007 reference tissue uptake is reported in accordance with the PROMISE protocol. A substantial number of patients present with higher uptake in the spleen than in parotid glands, for reasons that are currently unexplained. Care should be taken when interpreting these values until further studies are conducted. Key Points <Emphasis Type="BoldItalic">Question</Emphasis> The normal range for [18F]PSMA-1007 uptake values in PROMISE reference tissues are not well documented, challenging standardized lesion categorization in prostate cancer PET interpretation. <Emphasis Type="BoldItalic">Findings</Emphasis> In a multicenter cohort, splenic [18F]PSMA-1007 uptake exceeded parotid gland uptake in a notable subgroup (15%), leading to situations where PSMA expression scoring according to the PROMISE framework cannot be applied as intended. <Emphasis Type="BoldItalic">Clinical relevance</Emphasis> Unexpectedly high splenic uptake relative to parotid gland uptake of [18F]PSMA-1007 in some patients may affect lesion categorization; careful interpretation is advised. Graphical Abstract

Reference tissue uptake of [18F]PSMA-1007 in positron emission tomography of recurrent prostate cancer

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2026年4月23日

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Bendik Skarre Abrahamsen,
Ingerid Skjei Knudtsen,
Andreas Julius Tulipan,
Eivor Hernes,
Trond Velde Bogsrud,
Kirsten Margrete Selnæs,
Håkon Johansen,
Tone Frost Bathen,
Mattijs Elschot

摘要

Introduction

Semi-quantitative uptake measurements are part of the PROMISE framework for PET/CT interpretation of tracers targeting the prostate-specific membrane antigen (PSMA), where tumor uptake is compared to uptake in reference tissues. [18F]PSMA-1007 has primarily hepatobiliary excretion and it is suggested to use spleen as reference tissue instead of liver. The aim of this study is to investigate the normal range and interpatient variability of [18F]PSMA-1007 uptake in reference tissue for prostate cancer patients, with particular focus on the splenic uptake.

Materials and methods

A total of 102 [18F]PSMA-1007 PET/CT scans of prostate cancer patients with biochemical recurrence (BCR) from three hospitals were included in the analysis. SUV_max and SUV_mean measurements were performed in the blood pool, liver, spleen, and parotid glands. Results are reported as median with percentiles [5th, 95th].

Results

For 15/102 (15%) and 20/102 (20%) of the patients, the SUV_max and SUV_mean, respectively, were higher in the spleen than in the parotid glands. Median SUV_max of the reference tissues were 1.2 [0.6, 2.2] for blood, 15.8 [8.9, 26.2] for spleen, and 26.6 [14.5, 40.4] for the parotid glands. Median SUV_mean were 11.9 [6.6, 20.7] for spleen and 19.3 [11.2, 32.1] for the parotid glands.

Conclusion

In this multicenter cohort of BCR patients, [18F]PSMA-1007 reference tissue uptake is reported in accordance with the PROMISE protocol. A substantial number of patients present with higher uptake in the spleen than in parotid glands, for reasons that are currently unexplained. Care should be taken when interpreting these values until further studies are conducted.

Key Points

Question The normal range for [18F]PSMA-1007 uptake values in PROMISE reference tissues are not well documented, challenging standardized lesion categorization in prostate cancer PET interpretation.

Findings In a multicenter cohort, splenic [18F]PSMA-1007 uptake exceeded parotid gland uptake in a notable subgroup (15%), leading to situations where PSMA expression scoring according to the PROMISE framework cannot be applied as intended.

Clinical relevance Unexpectedly high splenic uptake relative to parotid gland uptake of [18F]PSMA-1007 in some patients may affect lesion categorization; careful interpretation is advised.

Graphical Abstract