The value of 18F-DCFPyL PET/CT in the treatment decision of castration-resistant prostate cancer patients

1552 Objectives: Prostate cancer is a common malignant tumor, the androgen deprivation therapy (ADT) is an important means of treatment for prostate cancer. The ADT works well at the initial stage and can significantly reduce the PSA level, but during the treatment process, after about 18-24 months, patients gradually develop resistance to ADT and enter castration-resistant prostate cancer (CRPC) stage. CRPC mainly refers to that in the process of castrating prostate cancer patients with drugs or surgery, serum testosterone reaches castrating level (<50ng/mL), but PSA still continues to rise and/or imaging findings of prostate cancer progress. CRPC stage is currently the focus and difficulty of prostate cancer treatment. Our purpose is to evaluate the role of 18F-DCFPyL PET/CT in the treatment decision of castration-resistant prostate cancer. Methods: We retrospectively analyzed the 18F-DCFPyL PET/CT images and clinical data of 22 castration-resistant prostate cancer patients, the number of positive lesions on PET/CT and the situation of their distribution in vivo were observed. Then, the subsequent treatment and serum PSA response were followed up. Results: The serum PSA of these 22 patients was 0.36 ng/ml to 86.5 ng/ml at the time point of the 18F-DCFPyL PET/CT scan. All of the 22 patients had positive lesion or lesions on PET/CT. There were 2 patients with intraprostatic focus but no distant metastatic lesion, among which 1 case (Figure 1)underwent radical prostatectomy and the postoperative PSA was reduced to 0.003ng/ml, and the other case was not treated and the PSA was in progress; 1 patient with intraprostatic focus and sacral metastasis, the PSA decreased to 0.001ng/ml after radiotherapy; 2 patients with intraprostatic focus and multiple metastases, of which 1 case received 177Lu-PSMA radionuclide treatment but was not effective (PSA continued to rise and died), and the other case was not treated and PSA was in progress; 11 patients with oligometastasis, among them, 8 cases received local radiotherapy and PSA decreased to ideal shape, 3 cases received local radiotherapy and PSA decreased significantly or continuously, and 3 cases were to be followed up; 6 patients with extensive metastasis, including 5 patients with no treatment and PSA progression , the other 1 patient was to be followed up. Conclusions: 18F-DCFPyL is highly expressed in castration-resistant prostate cancer patients with local recurrence and metastasis. 18F-DCFPyL PET/CT is of guiding significance for clinical staging of castration-resistant prostate cancer patients and subsequent treatment decisions, especially for patients with oligometastasis with low PSA, salvage therapy can be adopted and better efficacy can be achieved.1References: 1.Grubmuller B, Senn D, Kramer G, et al. Response assessment using (68)ga-psma ligand pet in patients undergoing (177)lu-psma radioligand therapy for metastatic castration-resistant prostate cancer. 2018