Abstract
BackgroundThe aim of the current study was to assess whether and to what extent monitoring response to treatment using prostate-specific membrane antigen (PSMA)-based positron-emitting tomography/computerized tomography (PET/CT) studies contribute clinically relevant data to routine clinical follow-up during treatment of patients with metastatic prostate cancer (PCa).ResultsFifty-two patients with metastatic PCa who underwent [68Ga]Ga-PSMA-11 PET/CT imaging and serum prostate-specific antigen (PSA) level measurements before and during treatment were investigated. Response was categorized by serum PSA dynamics according to improvement, stable disease, and disease progression and compared to change in imaging findings on pre- and post-treatment PET/CTs. McNemar’s test was used to assess agreement between PET/CT- and PSA-based responses to treatment.Thirty-four patients (65.4%) had compatible biochemical- and imaging-based response to treatment. However, the imaging and biochemical responses were discrepant in 18/52 patients (34.6%). PET/CT showed progressive disease in 5/52 patients (9.6%) and improvement/stable disease in 13/52 (25%) compared to biochemical assessment results. Discrepancy between imaging and biochemical response was most prominent in biochemically stable patients (90.9%), followed by patients with biochemical progression (33.3%), and in only few (8.7%) patients with biochemical improvement. The imaging-based response was suitable for choosing subsequent treatment in 22 of 30 patients (73.3%) with longer follow-up (median time of 10.3 months (IQR 6.3–18.2)). The relevance of the imaging methodology was reflected by its ability to assess individual lesions in cases of heterogeneous lesion responses, reveal the appearance of new lesions, and identify lesions that required specific consideration, such as targeted radiotherapy.ConclusionsResults of this retrospective analysis showed that biochemical responses to treatment and [68Ga]Ga-PSMA-11 PET/CT-based responses to treatment differ in one third of metastatic PCa patients. The latter additionally enabled lesion-based and not solely patient-based analysis. Monitoring response during treatment by [68Ga]Ga-PSMA-11 PET/CT is suitable for decision-making in patient management and choice of treatment in the majority of patients.
Highlights
Assessment of response to therapy in prostate cancer (PCa) patients relies on a combination of clinical parameters, the biochemical response as reflected by a change in serum prostate-specific antigen (PSA) levels, and on the morphological assessment on computerized tomographic (CT) imaging using the Response Evaluation Criteria in Solid Tumors (RECIST) [1,2,3,4]
Few studies have evaluated the use of choline tracers for monitoring response to treatment in PCa patients receiving abiraterone, enzalutamide, and docetaxel, with all showing some discrepancy between the response to treatment as assessed by choline-based positron-emitting tomography (PET/CT) and by biochemical response [5,6,7]
The findings of the current study revealed that biochemical-based and [68Ga]Ga-prostate-specific membrane antigen (PSMA)-11 positron-emitting tomography/computerized tomography (PET/CT)-based assessment of response to treatment may differ in one third of metastatic PCa patients
Summary
Assessment of response to therapy in prostate cancer (PCa) patients relies on a combination of clinical parameters, the biochemical response as reflected by a change in serum prostate-specific antigen (PSA) levels, and on the morphological assessment on computerized tomographic (CT) imaging using the Response Evaluation Criteria in Solid Tumors (RECIST) [1,2,3,4]. Monitoring response during treatment by [68Ga]Ga-PSMA11 PET/CT is suitable for decision-making in patient management and choice of treatment in the majority of patients
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