The Role of FDG PET for Early Prediction of Response after Two Cycles of Epirubicin + Cyclophosphamide Neoadjuvant Chemotherapy in Breast Cancer.

Abstract

Abstract Background: Previous studies showed a possible role of Fluorodeoxyglucose Positron Emission Tomography (FDG PET) in monitoring response to neoadjuvant chemotherapy (NACT) in breast cancer patients. Most studies, however, mixed various chemotherapy protocols. We assessed the ability of FDG PET to predict response after two cycles of epirubicin + cyclophosphamide (EC) and compared it with histopathological response as determined by the Sataloff scale after completion of chemotherapy.Material and Methods: From 07/2007 to 05/2009, 54 patients seen at Saint Louis hospital underwent FDG PET at baseline and after the second cycle of NACT. We present data for the first 22 consecutive patients for whom pathology data are available. Standard chemotherapy treatment was four cycles of epirubicin + cyclophosphamide followed by four cycles of docetaxel. The study was performed according to the guidelines of the institutional ethical committee. The standardized uptake value (SUVmax) of FDG was measured with a PET-CT instrument at baseline and after the second cycle of chemotherapy. The change in SUV was expressed as Δ SUVmax (%) = 100 X (2nd cycle SUVmax - baseline SUVmax)/baseline SUVmax. A Δ SUVmax cutoff value of -45% was used to differentiate metabolic responders and non-responders. Histopathological response was assessed on fresh surgical specimens (mastectomy or lumpectomy) by an experienced pathologist and graded according to the scale established by Sataloff: total or near-total therapeutic effect (grade A), more than 50% therapeutic effect but less than total or near-total effect (grade B), less than 50% therapeutic effect but visible effect (grade C), or no therapeutic effect (grade D). For the analysis, grades A and B were considered as histopathological responders and grades C and D were as non-responders.Results: Initial T-stage was T2 in 12 cases, T3 in 6 cases and T4 in 4 cases. There were 21 cases of invasive ductal carcinoma and 1 case of invasive lobular carcinoma. Mean SUVmax in initial PET was 7.22 (ranges from 2.7 to 18.5) and mean SUVmax after 2 cycles of chemotherapy was 4.77 (1.4-15.3). Breast-conserving surgery was performed in 12 patients and mastectomy in 10 patients. Nine (41%) of 22 patients were classified as histopathologic responders and 13 (59%) as non-responders. PET after two cycles of NACT revealed 9 patients (41%) as responders and 13 (59%) as non-responders. Among 9 metabolic responders, 7 were true positive, and 2 were false positive. Among 13 metabolic non-responders, 11 were true negative, and 2 were false negative. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of FDG PET after two cycles of NACT were 78%, 85%, 78%, 85% and 82% respectively.Discussion: NACT has proved useful in stage II and III breast cancer, to reduce tumour volume, increasing the chance of breast-conserving surgery. In order to minimize adverse effects of NACT, non-responders must be identified as early as possible. Our preliminary results on a small series of patients show that FDG PET can differentiate responders from non-responders with good accuracy after two cycles of neoadjuvant chemotherapy with EC. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5009.