Abstract AIM Evaluate within a pilot setup feasibility and safety of minimally invasive needle-biopsy of sentinel nodes guided by SPECT/US as compared to surgical removal while defining optimal needle for follow-up trial. METHOD AND MATERIALS As pretrial test phase of the MinimalSNB study, 38 breast cancer patients (6 centers) were taken a needle-biopsy of their sentinel lymph nodes (SLNs) under guidance of SPECT/US (SentiGuide by SurgicEye, Munich, DE). All patients were indicated for a surgical SLN biopsy which was performed immediately after the needle-biopsy. For the test phase, 4 different biopsy systems were tested: HistoCore 14G (BIP, Tuerkenfeld, DE), elite 10G and 13G (Mammotome, Cincinnati, OH, US) and CASSI II 10G (Scion Medical Technologies, Boston, MA, US). Histopathological examination (H&E, step-sectioning) of needle-biopsies and surgically removed SLNs were compared. RESULTS No single complication was reported. Occasionally, small hematomas could be found close to the SLN during surgery. Duration of complete procedure (imaging, needle placement, biopsy) took in average 17min. A learning curve was observed in duration (average after 5 biopsies 12min). 1-14 samples were taken of each SLN (average 5 samples). Final pathological examination of material harvested with both methods matched in 34 cases (33 negatives, 1 positive). The needle biopsy failed to detect metastases in 2 pN1 SLNs. In 1 case, the surgically resected tissue did not contain lymph nodes and the needle biopsy remained the only information on nodal status. In 1 case a metastasis found in needle-biopsy motivated a second reading of an originally negative SLN which resulted in the upstaging of the patient. In both cases a metastases was missed by needle-biopsy, the retrieved lymph tissue was minimal (1x 14G sample, 1x 10G sample tangential to node). CONCLUSION SPECT/US showed to be a valid method for percutaneous detection of SLNs and needle-guidance. Sampling SLNs with a needle seems safe and feasible. However it requires proper training and user experienced with axillary needle-biopsies. Retrieving more tissue (more cores and larger lumen needles) improves diagnostic power of needle-biopsy. These considerations will be taken within the upcoming MinimalSNB trial. CLINICAL RELEVANCE Sentinel lymph biopsy today is a surgical diagnostic procedure with an nonzero morbidity. Moving it out of the operating theatre to a needle-based intervention has a huge impact on the burden of this procedure for the patient as well as relevant improvements in logistics, workflow and radiation burden. Citation Format: Paepke S, Pfob CH, Ohlinger R, Gruber I, Thill M, Blohmer JU, Kuehn T, Hahn M, Kiechle M, Wendler T. Can sentinel node staging be performed using a minimally invasive needle-biopsy? Results of German multicentric pilot study. abstract. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-01-16.