PSMA and ¹⁸F-FDG PET Imaging in the Treatment of Metastatic Prostate Cancer with ²²³Ra: Initial Application and Experience

  Objective  To share our experience of the use of prostate specific membrane antigen (PSMA) and/or ¹⁸F-fluoroodexyglucose (¹⁸F-FDG) positron emission tomography (PET) in the setting of radium-223 dichloride (²²³Ra) in treatment of bone metastases of prostate cancer in order to broaden the know-ledge of application of ²²³Ra in China.

  Methods  Retrospective analysis was conducted for the patients with advanced prostate cancer treated with ²²³Ra in Peking Union Medical College Hospital between September 2021 to January 2023.The treatment outcomes and survival status were recorded.Characteristics of bone scans and PET imaging (including PSMA PET and/or ¹⁸F-FDG PET) before and after treatment were summarized.

  Results  Nine patients were enrolled (2 additional patients were excluded for the reason of visceral metastases confirmed by pretreatment PET imaging), among whom 8 patients had metastatic castration resistant prostate cancer and 1 had metastatic hormone-sensitive prostate cancer.In total the 9 patients received 36 doses of ²²³Ra, and the numbers of patients receiving 6, 5, 4, 2, and 1 doses were 3, 1, 2, 2, and 1, respectively.At the middle or end of treatment, there was 1 case of partial remission, 1 case of stable disease, 6 cases of progressive disease, and 1 case was switched to endocrine therapy after 1 shot of ²²³Ra treatment so that the efficacy was not evaluated.At the time of the last follow-up (March 15, 2023), among the 9 patients, 4 died (1 due to heart failure and 3 due to disease progression) and 5 survived.For patients who died or with progressive disease, there was an inconsistency between the metastases shown on baseline PET images and bone scans, with the former modality revealing more bone metastases.PET imaging especially PSMA PET was more accurate than bone scan in assessing response and could avoid bone scintillation.

  Conclusions  PSMA PET and/or ¹⁸F-FDG PET could help detect visceral metastases and assist in patient screening.The inconsistency between baseline PET images and bone scan images suggests a worse outcome of ²²³Ra treatment.During the efficacy evaluation process, PSMA and/or ¹⁸F-FDG PET (especially PSMA PET) also outperforms bone scan.