Cancer detection in patients with prostate-specific antigen levels within the grey zone: can synthetic magnetic resonance imaging aid in the differentiation between prostate cancer and noncancerous lesions?

Background: The detection of prostate cancer (PCa) via conventional magnetic resonance imaging (MRI) in patients with prostate-specific antigen (PSA) levels within the grey zone remains challenging. Whether synthetic MRI can provide supplementary benefits for the accurate diagnosis of PCa in this specific population is still unknown. This study aims to investigate the diagnostic performance of synthetic MRI for differentiating PCa lesions from noncancerous lesions in patients with PSA levels within the grey zone (4-10 ng/mL).

Methods: Clinical and MRI data, including synthetic MRI data of patients suspected of having PCa between August 2020 and August 2022, were retrospectively collected from The First Affiliated Hospital of Sun Yat-sen University and Sun Yat-sen University Cancer Center. Patients with PSA levels ranging from 4-10 ng/mL were enrolled. Pathology was obtained either from transrectal ultrasound-guided biopsy or radical prostatectomy. Regions of interest were manually drawn by two independent radiologists, and the values of quantitative parameters, including longitudinal relaxation time (T1), transverse relaxation time (T2), proton density (PD), and apparent diffusion coefficient (ADC), were separately measured. Interobserver agreement was evaluated using the interclass correlation coefficient (ICC). The differences in quantitative parameter values between PCa and noncancerous lesions were assessed using an independent sample t-test or the Mann-Whitney U test. Receiver operating characteristic curve analysis was performed to evaluate the diagnostic performance of each parameter (T1, T2, PD, and ADC values), as well as their combination. P<0.05 indicated statistical significance.

Results: A total of 130 patients were enrolled in this study, with a mean age of 67.32±8.87 years. The interobserver agreement of all the T1, T2, PD, and ADC values was classified as good or above (ICC =0.60-1.00). The means of the T1, T2, PD, and ADC values were significantly different between PCa and noncancerous lesions (P=0.022, P<0.001, P=0.035, P<0.001, respectively). Notably, the ADC value demonstrated superior diagnostic performance compared to that of the other parameters, with an area under the curve (AUC) of 0.854 [95% confidence interval (CI): 0.781-0.909]. The combination of T1, T2, PD, and ADC values had a greater diagnostic performance (AUC =0.853, 95% CI: 0.781-0.909) than the T1 (AUC =0.622), T2 (AUC =0.721), or PD (AUC =0.608) values for differentiating PCa lesions from non-cancerous lesions. However, compared to the difference in the ADC value, no significant difference was found (P=0.982).

Conclusions: Quantitative parameters, including T1, T2, and PD, derived from synthetic MRI can be applied to differentiate PCa lesions from noncancerous lesions in patients with PSA levels within the grey zone. However, when these parameters were combined with the ADC, the diagnostic performance did not improve compared to that with the ADC value alone.