PURPOSE & INTRODUCTION Comparison between 18F-FDG uptake patern and apparent diffusion coefficient value obtained from diffusion-weighted magnetic resonance imaging on the detection of primary tumour and axillary metastases in breast carcinoma   Aynur Ozen1, Tarik Sayin2, Ozgul Ekmekcioglu 1, Serdar Altinay3, Eylem Bastug 1, Ali Muhammedoglu 3, Atilla Celik4, Ramazan Albayrak2 Departments of Nuclear Medicine1, Radiology2, Pathology3 and General Surgery4, Bagcilar Training and Research Hospital, Istanbul, Turkey ANNUAL CONGRESS OF THE EUROPEAN ASSOCIATION OF NUCLEAR MEDICINE OCTOBER 10-14, 2015 HAMBURG/GERMANY BAĞCILAR TRAINING AND RESEARCH HOSPITAL ISTANBUL/TURKEY Figure PURPOSE & INTRODUCTION Breast carcinoma (BC) is the most common type of cancer in female population1. Breast magnetic resonance maging (MRI) detects increased blood flow and tissue resolution in order to diagnose cancer, thus, being more sensitive and accurate than mammography and ultrasonography2. When breast MRI findings are suspicious, diffusion-weighted magnetic resonance imaging (dw-MRI) provides additional information about microstructural characteristics of tissue and it is increasingly performed in the evaluation of tumours3. Furthermore, the apparent diffusion coefficient (ADC) value obtained from dw-MRI was useful in differentiating between benign and malignant breast lesions4-8. Our objective was to compare SUVmax patern in 18F-FDG PET/CT and ADC value of dw-MRI for the detection of primary tumour and axillary lymph node (ALN) metastases of BC. SUBJECTS & METHODS This retrospective study included 42 female patients (mean age, 51,3012,26 years; age range, 29-78 years) with BC. Thirty-eight patients had invasive ductal carcinoma, one of them with sarcomatoid differentiation, 1 invasive lobular carcinoma, 1 mixed type, 1 mucinous and 1 medullar BC. After pre-operative staging with 18F-FDG PET/CT and dw-MRI, mastectomy or breast conserving surgery with ALN disection or sentinel lymph node biopsy was performed. For histopathologic evaluation, Modified Bloom Richardson grading system was used. Furthermore, oestrogen (ER), progesteron (PR) receptor expression and Her-2/neu statuses were determined. SUVmax was measured from primary tumour, metastatic ALN, the normal parenchymas of breast, lung and liver. Also, ADC was measured from breast tumour and metastatic ALN. SUVmax ratios was calculated following as: TumourSUVmax/breastSUVmax, TumourSUVmax/lungSUVmax, TumourSUVmax/liverSUVmax. (a) Transaxial PET/CT images in supine position, (b) images at prone position obtained shortly after supine position images for accurate localization of primary tumour and (c) ADC map in diffusion weighted imaging display, in a 40 years old woman with IDBC and 2.5cm tumour size, grade 3, ER-PR positive, 1+ Her2/neu status in right breast. ROIs are shown on a and b for measuring SUVmax, and on c for measuring the mean ADC value. DISCUSSION & CONCLUSION Our study suggested that a) the primary lesions detection rate of both 18F-FDG PET/CT and dw-MRI was high, 95.3%. b) Both modalities had the same specificity for the detection of ALN metastases, but the 18F-FDG PET/CT scan had lower sensitivity than dw-MRI and c) SUVmax and SUVmax ratios were more compatible with pathological parameters than ADC value. These two imaging modalities might play a supplemantary role in the detection of BC and ALN metastases. REFERENCES Carlson RW, Allred DC, Anderson BO, et al. NCCN Breast Cancer Clinical Practice Guidelines Panel: Breast cancer. Clinical practice guidelines in oncology. J Natl Compr Canc Netw 2009;7:122-192. Biglia N, Mariani L, Sgro L, et al. Increased incidence of lobular breast cancer in women treated with hormone replacement therapy: implications for diagnosis, surgical and medical treatment. Endocr Relat Cancer 2007;14:549-567. Koh DM, Takahara T, Imai Y, et al. Practical aspects of assessing tumors using clinical diffusion-weighted imaging in the body. Magn Reson Med Sci 2007;6:211-224. Guo Y, Cai YQ, Cai ZL, et al. Differentiation of clinically benign and malignant breast lesions using diffusion-weighted imaging. J Magn Reson Imaging 2002;16:172-178. Hatakenaka M, Soeda H, Yabuuchi H, et al. Apparent diffusion coefficients of breast tumors: clinical application. Magn Reson Med Sci 2008;7:23-29. Kinoshita T, Yashiro N, Ihara N, et al. Diffusion-weighted half-Fourier single-shot turbo spin echo imaging in breast tumors: differentiation of invasive ductal carcinoma from fibroadenoma. J Comput Assist Tomogr 2002;26:1042-1046. Kuroki Y, Nasu K, Kuroki S, et al. Diffusion-weighted imaging of breast cancer with the sensitivity encoding technique: analysis of the apparent diffusion coefficient value. Magn Reson Med Sci 2004;3:79-85. Woodhams R, Matsunaga K, Kan S, et al. ADC mapping of benign and malignant breast tumors. Magn Reson Med Sci 2005;4:35-42. RESULTS Results showed that the primary lesion detection rate for PET/CT and dw-MRI was 95.3%. The 18F-FDG PET/CT scan had lower sensitivity in detecting of ALN metastases than dw-MRI, while their specificities were equal. Higher SUVmax and/or SUVmax ratios correlated with stage T2 tumours, with histologic grade 3, and with negative ER and PR receptor status. There was no correlation between ADC and SUVmax or SUVmax ratios both primary tumour and metastatic axillary lymph node.