Serial FDG-PET imaging of metastatic prostate cancers reveals intrapatient intermetastases polyclonality through same patient heterogeneous responses to systemic therapy.

Abstract

e590 Background: Although intrapatient prostate cancer (PCa) metastasis polyclonality has been recently characterized by genomic and transcriptomic studies, systemic treatment response heterogeneity has yet to be reported or imaged. It remains unknown if polyclonal differentiation leads to heterogeneous treatment responses between metastases in a single patient undergoing therapy. Methods: Between 2010 and 2015, fifteen patients with metastatic PCa were imaged by FDG-PET/CT before and during systemic therapy, and metabolic response was recorded for individual metastatic lesions. Intermetastasis heterogeneity was defined by opposite metabolic responses of at least two metastases from the same compartment (bone or soft tissue) between the two scans. We examined intrapatient intermetastasis heterogeneity of response to systemic therapy based on the assessment of metabolic response in a total of 165 individual lesions (change in SUVmax, complete response, or new lesion). Change in total lesion glycolysis (TLG) was assessed for each patient. Biochemical response and progression-free survival (PFS) were also recorded. Results: Intrapatient intermetastasis response heterogeneity was found in 40% of cases. In univariate statistical analysis, response heterogeneity was associated with a decrease in PFS (p-value= 0.001), but not with age, CRPC status, Gleason score, PSA-DT, TLG, maximum SUVmax, or sum of SUVmax. In two cases, new metastasis and complete metastasis responses were observed in the same patients. Conclusions: Our results suggest that systemic therapies can induce heterogeneous responses among individual metastases in patients with PCa, supporting the polyclonal evolution of PCa in advanced disease. Molecular imaging may thus be useful to identify clinical resistance earlier after therapy initiation and could also enable targeted biopsy of resistant clones for molecular analysis.