Abstract
BackgroundTo compare the value of interim 18F-FLT-PET and 18F-FDG-PET for predicting treatment outcomes in patients with metastatic breast cancer after salvage therapy.MethodsPatients with metastatic breast cancer received PET/CT using 18F-FLT and 18F-FDG at baseline, after the 1st and 2nd cycle of systemic chemotherapy. The clinical response was classified according to Response Evaluation Criteria in Solid Tumors 1.1 based on contrast-enhanced CT after 3 months of systemic chemotherapy. The metabolic response on PET was assessed according to European Organization for Research and Treatment of Cancer criteria or PET Response Criteria in Solid Tumors (PERCIST) and was correlated to the clinical response, overall survival (OS), and progression-free survival (PFS).ResultsTwenty-five patients entered final analysis. On 18F-FDG-PET, clinical responders after 2 chemotherapy cycles (post-2c) had a significantly greater reduction of maximal standardized uptake value (SUV) and the peak SUV corrected for lean body mass (SULpeak) of the tumor than non-responders (P = 0.030 and 0.003). Metabolic response determined by PERCIST on post-2c 18F-FDG-PET showed a high area under the receiver operating characteristics curve of 0.801 in predicting clinical response (P = 0.011). Patients who were metabolic responders by PERCIST on post-2c 18F-FDG-PET had a significantly longer PFS (53.8% vs. 16.7%, P = 0.014) and OS (100% vs. 47.6%, P = 0.046) than non-responders. Survival differences between responders and non-responders in the interim 18F-FLT-PET were not significant.Conclusions18F-FLT-PET failed to show an advantage over 18F-FDG-PET in predicting the treatment response and survival in patients with metastatic breast cancer. Assessment of treatment outcome by interim 18F-FDG-PET may aid treatment.Trial registrationThe study was retrospectively registered on 02/06/2020 on Clinicaltrials.gov (identifier NCT04411966).
Highlights
To compare the value of interim 18F-FLT-positron emission tomography (PET) and 18F-FDG-PET for predicting treatment outcomes in patients with metastatic breast cancer after salvage therapy
We measured the maximum standardized uptake value (SUV) (SUVmax) and the peak SUV corrected for lean body mass (SULpeak) within a region of interest (ROI) [17]
Baseline patient characteristics and clinical treatment response A total of thirty-two patients were enrolled in this study
Summary
To compare the value of interim 18F-FLT-PET and 18F-FDG-PET for predicting treatment outcomes in patients with metastatic breast cancer after salvage therapy. The change of tumor size on computed tomography (CT) is the current standard for monitoring tumor response in mBC. Clinical trials have shown that the response based on size criteria may not be a suitable surrogate to predict survival in breast cancer [2, 3]. In this context, molecular imaging techniques such as positron emission tomography (PET) imaging have been advocated for therapy response evaluation
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