Prognostic value of FDG, PSMA, and DOTATATE uptake on PET imaging in metastatic castration-resistant prostate cancer (mCRPC).

Author(s): Frederic Pouliot¹; Fred Saad²; Étienne Rousseau³; Patrick O. Richard⁴; Atefeh Zamanian¹; Stephan Probst⁵; Eric Levesque¹; Vincent Castonguay⁶; Nicolas Marcoux⁷; Daniel Juneau⁸; Michele Lodde⁹; Jean-Baptiste Lattouf¹⁰; François-Alexandre Buteau¹¹; Zineb Hamilou¹²; Michel Pavic¹³; Jean-François Castilloux¹³; Guillaume Bouvet¹¹; Amélie Tetu¹⁴; Brigitte Guérin³; Jean-Mathieu Beauregard¹¹

Source: https://doi.org/10.1200/JCO.2024.42.4_suppl.3

Dr. Maen Hussein's Thoughts

It might be costly to get the PET scans but helps with prognosis and directing patients to palliative care since positive lesions in all predicts shorter overall survival.

BACKGROUND

In mCRPC, fluorodeoxyglucose (FDG) and prostate-specific membrane antigen (PSMA) PET/CT are often used in combination for selecting patients for PSMA-radioligand therapy (PSMA-RLT). Few studies have specifically assessed the prognostic value of FDG+/PSMA- lesions, which exclude patients from PSMA-RLT. Also, little is known about the significance of somatostatin receptor expression, a potential biomarker of neuroendocrine differentiation of mCRPC, which can be assessed with DOTATATE-PET/CT. 3TMPO is a prospective study in progressing mCRPC patients who were imaged with up to 3 PET tracers. Here, we report on patient’s overall survival (OS), with respect to the presence of FDG+/PSMA- and DOTATATE+ lesions.

METHODS

In 3TMPO (NCT04000776, protocol in PMID 34674367), all patients had 68Ga-PSMA-617 and 18F-FDG PET/CT scans. A 68Ga-DOTATATE scan was ordered if an FDG+/PSMA- lesion was found. For all tracers, positivity was defined as lesion SUVpeak being 1.5x higher than liver SUVmean. Kaplan-Meier with log-rank test was used to assess the difference in OS between groups. Cox regression model was used to quantify the effect of factors predictive of OS.

RESULTS

The median [95% CI] OS of the 98 enrolled patients was 10.2 [8.5-11.8] mo. At least one FDG+/PSMA- lesion was found in 45 (45.9%) patients and their OS was shorter than that of the others: 5.6 [4.3-6.9] vs. not reached (p=0.0001). Six (16.2%) of 37 patients who underwent 68Ga-DOTATATE-PET had ≥1 DOTATATE+ lesion and their OS was shorter than that of patients without a DOTATATE+ lesion: 3.0 [2.2-3.7] vs. 6.4 [1.6-11.1] mo. (p=0.0004). Characteristics significantly associated with worse OS were ECOG, ISUP grade, number of metastases, number of lines of therapy, presence of visceral metastases, FDG and PSMA molecular tumor volumes (MTV) (p<0.05). In a multivariate analysis adjusted for the number of metastases and of treatment lines, the presence of an FDG+/PSMA- lesion increased the risk of death (HR [95% CI]=2.4 [1.4-4.3], p=0.002), and this was also significant after adjusting for both PSMA and FDG-MTV (HR [95% CI]=2.9 [1.4-5.8], p=0.003).

CONCLUSIONS

mCRPC patients harboring FDG+/PSMA- lesion(s) had a shorter OS than those who did not, and their prognosis was even poorer if they also had DOTATATE+ lesion(s). Upfront FDG/PSMA-PET followed by DOTATATE-PET might help clinicians to guide patient towards palliative care vs. further systemic therapy, including PSMA-RLT.

Author Affiliations

¹CHU de Québec – Université Laval, Québec, QC, Canada; ²Centre Hospitalier de l’Université de Montréal, Université de Montréal, Montréal, QC, Canada; ³CIUSSS de l’Estrie – CHUS (Hôpital Fleurimont), Sherbrooke, QC, Canada; ⁴CIUSSS de l’Estrie – CHUS (Hôpital Fleurimont), Sherbrooke, QC, Canada; ⁵Jewish General Hospital, Montréal, QC, Canada; ⁶CHU de Québec – Hotel Dieu de Québec, Québec, QC, Canada; ⁷Hotel Dieu de Quebec, Quebec, QC, Canada; ⁸Centre Hospitalier de l’Universite de Montreal, Montreal, QC, Canada; ⁹Centre Hospitalier Universitaire Pavillon l’Hôtel-Dieu de Québec, Québec, QC, Canada; ¹⁰Centre Hospitalier de l‘Université de Montréal/CRCHUM, Montreal, QC, Canada; ¹¹CHU de Québec – Université Laval, Québec, QC, Canada; ¹²Centre Hospitalier de l’Université de Montréal, Montreal, QC, Canada; ¹³CIUSSS de l’Estrie- CHUS (Hôpital Fleurimont), Sherbrooke, QC, Canada; ¹⁴CIUSSS de l’Estrie – CHUS, Sherbrooke, QC, Canada

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