Detection Rate of 18F-Choline Positron Emission Tomography/Computed Tomography in Patients with Non-Metastatic Hormone Sensitive and Castrate Resistant Prostate Cancer

The aim of our study was to assess the detection rate of 18F-choline PET/CT in non-metastatic hormone-sensitive prostate cancer (hsPCa) and non-metastatic castrate resistant prostate cancer (CRPCa), based on the criteria proposed in the phase III SPARTAN trial and GS>8. We conduct a retrospective, multicentric study based on data from four Italian nuclear medicine departments (collected from 2008-2019) using different PET/CT systems (Philips, GE, Siemens). Of more than 2500 men who underwent 18F-choline PET/CT for PCa biochemical recurrence after treatment of the primary tumor with radical prostatectomy or radiation therapy, were enrolled in the study only those with 1) histologically proven PCa; 2) a non-metastatic disease in accordance with conventional imaging findings; 3) a PSA doubling time (PSAdt) <10 months; 4) a Gleason Score (GS) >8; 5) no pelvic node > 2 cm, and 6) a PSA level at PET time < 20 ng/mL. Patients were sorted into hsPCa or CRPCa groups when a rising PSA value was reported respectively in not-ongoing hormonal therapy and in ongoing hormonal therapy subjects at the time of PET/CT imaging. PET images were assessed by two physicians with more than 5-year experience in 18F-choline PET/CT reading. Doubtful interpretations were solved by consensus between the two physicians. Out of 140 selected patients, 59% were hsPCa and 41% CRPCa, and differences between the two groups were found only in primary tumor treatment and GS. A positive pet scan was found in 99/140 patients (70.7%) without any statistical difference for PET findings in the two groups of patients (see the below figure).

Assessing predictors of positive PET/CT in univariable and multivariable logistic regression analyses, we found that there wasn’t any significant increase in the risk of having a positive PET/CT scan in CRPCa vs hsPCa. Moreover, comparative ROC curves for either PSA levels at the PET time and for PSAdt levels didn’t find any statistically significant difference between the groups. Evaluating PSA and PSAdt cut-off values in hsPCa and CRPCa, we found that the association between PSA level > 1.3 ng/mL and PSAdt > 3.7 months can increase the detection rate of 18F-Choline PET/CT mainly for the presence of distant organ metastases both in CRPCa and in hsPCa patients (see below table).

	hsPCa			CRPCa
	Cut-off	Sensitivity	Specificity	Cut-off	Sensitivity	Specificity
PSA PET (all)	1.62	72%	67%	1.3	84%	57%
PSA PET (rT)	0.7	95%	31%	7.3	56%	69%
PSA PET (rN)	4.06	46%	71%	1.40	88%	39%
PSA PET (rM)	0.84	96%	44%	9.8	52%	87%
PSAdt PET (all)	5.9	86%	48%	3.7	59%	79%
PSAdt PET (rT)	6.3	5%	77%	2	100%	29%
PSAdt PET (rN)	1.5	21%	88%	1.6	92%	21%
PSAdt PET (rM)	5.4	25%	59%	4.1	56%	68%

rT=recurrence in prostate gland or prostatic fossa; rN=recurrence in lymph nodes; rM=recurrence in distant lymph nodes or organs; hs=hormone sensitive; CR=castrate resistant; PCa=prostate cancer

In conclusion a selected population of patients, undergoing or not hormonal therapy, 18F-Choline PET/CT scan is positive in more than 65% of cases, changing the status from a non-metastatic disease to a metastatic one. The rate of positive 18F-Choline PET/CT is similar in hsPCa and CRPCa in case of low PSAdt and high GS, so non metastatic patients should be assessed by molecular imaging to choose the most appropriate therapeutic approach.

Written by: Fabio Zattoni, Paolo Artioli, Marta Burei, Agostino Chiaravalloti, Franca Chierichetti, Davide Donner, Stefano Panareo, Ilaria Rambaldi, Orazio Schillaci, Fabrizio Del Moro, Laura Evangelista

Clinical Urology, Azienda Ospedaliera Universitaria Integrata di Udine, Udine, Italy., Nuclear Medicine, Department of Medicine - DIMED, University of Padua, Padua, Italy., Nuclear Medicine, Veneto Institute of Oncology IOV - IRCCS, Padua, Italy., Department of Biomedicine and Prevention, University Tor Vergata, Rome, Italy., Nuclear Medicine, S. Chiara Hospital, Trento, Italy., Nuclear Medicine, Diagnostic Imaging and Laboratory Medicine Department, University of Ferrara, Ferrara, Italy., Department of Surgery, Oncology, and Gastroenterology, Urology Unit, University of Padua, Padua, Italy., Nuclear Medicine, Department of Medicine - DIMED, University of Padua, Padua, Italy

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