Abstract P4-01-10: Preoperative [18F]-fluoro-3’-deoxy-3’-L-thymidine positron emission tomography computed tomography (FLT-PET/CT) to predict early response to neoadjuvant chemotherapy in patients with primary breast cancer: Exploratory experience

Background Neoadjuvant chemotherapy (NAC) plays a crucial role in the treatment of breast cancer (BC) with not only the possibility to increase the breast conservative surgery but also to monitor in vivo the response of the primary tumor. It is well established that conventional radiological assessment (mammography, breast/axilla ultrasound) are unable to evaluate accurately NAC response. New metabolic methods of imaging must be identified to select non responder patients (pts), in order to change early the therapeutic strategy. [18F]FLT is a new tracer that visualises cellular proliferation and [18F]FLT-PET/CT uptake could reflect the tumour cell proliferation rate. Objective The aim of this exploratory study was to analyze the diagnostic role of pre-operative [18F]FLT-PET/CT in early prediction of response in pts with BC treated with NAC. Patients and methods Fifteen pts with diagnosis of operable or locally advanced BC were evaluated; pts with inflammatory BC were not eligible. After clinical and radiological diagnosis of BC [18F]FLT-PET/CT was performed; histological diagnosis by core-needle was subsequently done. After baseline, [18F]FLT-PET/CT was repeated then the first cycle of NAC and before surgery. Conventional assessments were performed at the same points. Clinical examinations were done before each cycle of NAC. All pts received an anthracycline-taxane based regimen for 6-8 cycles; trastuzumab were administered in HER2+ BC (5/15). Type of surgery was defined according to initial stage and residual disease. Results All but one pts have completed NAC, surgery was performed in all pts and pathological response was available in 15/15. 2/15 obtained pCR and non invasive BC was detected in one patient. This data were strictly related with a metabolic response predicted by [18F]FLT-PET/CT at the first assessment and before surgery. However, metabolic responses, even if not complete, were closely associated to the histopathologic result. 12/15 with positive post-chemotherapy [18F]FLT-PET/CT had residual disease. Minor or no change of uptake, early detected after the first cycle of NAC was subsequently confirmed at the end of the therapy. The only patient that progressed during NAC, had an initial metabolic response and subsequent clinical suspicious of tumor progression was confirmed by an increased [18F]FLT-PET/CT uptake. Conclusion [18F]FLT-PET/CT seems to be a powerful diagnostic tool to evaluate the effectiveness of NAC and it seems to be possible to predict the preoperative histological response after the first cycle of chemotherapy and before surgery. On the basis of the results of this exploratory experience [18F]FLT-PET/CT should be recommended for an extended application to monitor and to early predict the response/non response to anticancer treatment. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-01-10.