OBJETIVE To evaluate the 18F-FDG PET/CT capacity for the detection of axillary metastases and compare results with sentinel lymph node biopsy (SLNB).MATERIAL AND METHODS: 99 female patients with clinical T1T2N0 breast cancer were included. Patients with recent breast or axillary surgery, T3T4 disease, ductal carcinoma in situ, inflammatory carcinoma, uncontrolled diabetes mellitus and pregnant or lactation patients were excluded. Pre-operative FDG PET-CT was performed 15 days before surgery, SLNB took place with the combined method (radioisotopes and patent blue). Pearson and Spearman correlation test were used to evaluate association of main variables with a significance level (p) of 0.05.RESULTS: Breast PET-CT results: 80 positive PET/CT. Negative PET/ CT in 19 patients (4invasive lobular carcinoma, 7 tumors <7mm) Sensitivity 81%, specificity 100%.97 patients were operated (2 were stage IV with no surgery criteria). We found significant correlation of the FDG tumor uptake (SUV) with tumor size (p< 0.0001), histological grade (p< 0.009), nuclear grade (p<0.001), mitotic grade (p< 0.007) and Ki 67 (p< 0.0001).In all cases the correlation was positive.There was no correlation with hormonal receptors rate.Axillary PET CT results: positive PET/CT in 16 patients (16%). Of this 6 SNLB were negative (FPR= 9%). Specificity 91%, PET /CT were negative in 81 patients (84%), 17 had axillary metastases(5 micrometastases, 2 isolated tumor cells and 2 lobular carcinoma).Sensitivity:37%.FNR=63%. Correlation of histopatological axillary metastases was positive with breast tumor SUV (P<0.0002) and tumor size (p<0.01), but was not significant with histological, nuclear and mitotic grade, Ki 67,hormonal receptor rate and molecular subtype CONCLUSION: 1- PET / CT does not provide benefits for axillary staging in initial stages due to its low spatial resolution (6-8 mm) 2 –A negative axillary by PET/CT does not replace the sentinel node technique. 3 – We can suspect the presence of axillary metastases when there is an intense FDG uptake in the breast tumor. Citation Format: Cristina Noblia, Eugenia Azar, Dolores Mansilla, Amilcar Osorio, Eduardo Armanasco, Diana Montoya, Martin Ipiña, Gaston Berman, Eduardo Gonzalez, Christian Gonzalez, Gabriel Bruno, Patricia Parma, Carla Pulero, Ana Alvarez. Role of 18 FDG PET/CT in axillary staging in early breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-01-16.