Hybrid imaging with [68Ga]PSMA-11 PET-CT and PET-MRI in biochemically recurrent prostate cancer

Aim To compare [Ga-68]PSMA-11 PET-CT, [Ga-68]PSMA-11 PET-MRI and MRI in a cohort of prostate cancer (PCa) patients in biochemical recurrence after initial curative therapy. Materials and methods Fifty-three patients with biochemically recurrent PCa underwent whole-body [Ga-68]PSMA-11 PET-CT 1 hour post-injection (p.i.) followed by [Ga-68]PSMA-11 PET-MRI 2.5 hours p.i., including a multiparametric MRI pelvic protocol examination. Imaging data analysis consisted of visual (qualitative) evaluation of the PET-CT, PET-MRI and MRI scans, as well as semi-quantitative and quantitative analyses of the PET and MRI data, including calculation of the parameters standardized uptake value (SUV) and apparent diffusion coefficient (ADC) derived from the PCa lesions. Association analysis was performed between imaging and clinical data, including PSA level and Gleason score. The results were considered significant for p-values less than 0.05 (p < 0.05). Results The hybrid imaging modalities [Ga-68]PSMA-11 PET-CT and PET-MRI were positive in more patients than MRI alone. In particular, PET-CT detected lesions suggestive of PCa relapse in 34/53 (64.2%), PET-MRI in 36/53 (67.9%) and MRI in 23/53 patients (43.4%). While no significant differences in lesion detection rate were observed between PET-CT and PET-MRI, the latter was particularly efficient in detection of local recurrences in the prostate bed mainly due to the contribution of the MRI part of the modality. Association analysis revealed a statistically significant increase in the probability of a positive scan with increasing PSA levels for all imaging modalities. Accordingly, there was no significant association between scan positivity rate and Gleason score for any imaging modality. No significant correlation was observed between SUV and ADC values in lymph node metastases. Conclusion [Ga-68]PSMA-11 PET-CT and PET-MRI provide equally good detection rates for PCa recurrence, both outperforming stand-alone MRI.

Automated summary

[Ga-68]PSMA-11 PET-CT and PET-MRI provide equally good detection rates for prostate cancer recurrence, both outperforming stand-alone MRI. PET-MRI is particularly efficient in detecting local recurrences in the prostate bed, while there were no significant differences in lesion detection rate between PET-CT and PET-MRI. The probability of a positive scan significantly increased with increasing PSA levels for all imaging modalities.