136P Clinical implications of non-breast cancer related findings in breast cancer patients undergoing PET/CT scan prior to neoadjuvant systemic therapy

Breast cancer patients undergoing PET/CT scans for neoadjuvant systemic therapy may have non-breast cancer (BC) related finding. The aim of this study is to describe the incidence, additional work-up and possible impact of these findings. We included BC patients who underwent a PET/CT scan in our institute between 2011-2019 prior to neoadjuvant systemic therapy. An additional finding was defined as a non-physiologic abnormal lesion only depicted by PET/CT. Patients with a BC-related or no additional finding were excluded. For the remaining patients with a non-BC related additional finding, we retrospectively gathered information on the additional work-up and the clinical consequences. Of the 1337 patients included, 561 had additional findings on PET-CT, of whom 258 had a non-BC related additional finding. Further work-up was conducted in 202 patients (78%), including 282 examinations during initial work-up. In these 202 patients the non-BC related findings were detected in the endocrine region (26%), gastro-intestinal region (16%), lungs (15%), bones (14%), distant lymph nodes (11%), urogenital region (11%), liver (10%) and other (5%). In the end, 17 (8%) of the 202 patients were diagnosed with malignant and 138 patients (68%) with benign lesions. Only 8 patients (4%) had an additional non-BC related finding that was considered a more prognosis-determining diagnosis than their breast cancer disease. Malignant and prognosis-determining non-BC related additional findings mostly occurred in the endocrine, gastro-intestinal and urogenital region. PET/CT scans used for dissemination imaging in breast cancer patients detect a high number of non-BC related additional findings, with the majority being clinically irrelevant and causing a relatively large amount of unnecessary additional work-up. Additional non-BC related findings in the endocrine, gastro-intestinal and urogenital region have a higher change of being malignant. Clinicians should be aware of potential non-BC related PET/CT findings and carefully consider the clinical implications.