Background. Radioligand therapy (RLT) with 225Ac-PSMA is a new promising method for the treatment of metastatic castration-resistant prostate cancer (mCRPC), requiring a detailed assessment of the therapeutic effect. The non-invasive and radiation-free whole-body MRI method provides information on both skeletal and extraskeletal tumor foci, structured using the Met-RADS-P system and including a detailed assessment of the treatment outcome. Aim. To determine the capabilities of WB-MRI with Met-RADS-P criteria in the interim assessment of the effectiveness of radiotherapy with the drug «225Ac-PSMA» in patients with metastatic castration-resistant prostate cancer (mCRPC) in comparison with the dynamics of PSA. Methods. WB-MRI was performed in 20 patients with mCRPC twice: before the introduction of 225Ac-PSMA in doses from 6 to 12 MBq and 1-2 months after the first course of radiotherapy with parallel determination of the PSA level. Prospective assessment of the response to radiotherapy was carried out according to the Met-RADS-P criteria for WB-MRI and PCWG for PSA dynamics. The reproducibility of the Met-RADS-P criteria was determined by repeat reading of WB-MRI after 6 months by the same radiologist. Results. After 1 course of radiotherapy, progression according to Met-RADS-P criteria was detected in 4 patients (20%), and in three of them - at an earlier time point than according to PSA data. More than half of the patients had a discordant response, including three with progression. Differences in PSA dynamics were revealed with unidirectional positive and various variants of discordant response according to the Met-RADS-P criteria. With a unidirectional response, the integrated assessment according to Met-RADS-P correlated well with the biochemical response for the patient. Met-RADS-P criteria had excellent reproducibility for the primary RAC pattern and for the integrated response for the patient. For the secondary RAC pattern, reproducibility was significant. Conclusion. Met-RADS-P criteria in WB-MRI in patients with mCRPC allowed to detect progression for both extraskeletal and skeletal lesions at earlier time points than PSA dynamics. Further study of the prognostic significance of Met-RADS-P criteria in radioligand therapy with the drug «225Ac-PSMA» is required.
Березовская et al. (Fri,) studied this question.