Mieke Bus

5 79 In UTUC, a high rate (43 to 96%) of tumor upgrading and -staging is reported, particularly in low-grade tumorbiopsies. (3, 14) Anatomical limitations of the upper urinary tract are the most important cause of inaccurate biopsy. Instrumental maneuvers are hampered and the small caliber of biopsy graspers/ baskets leads to small sampling and crushed biopsies. (2) Despite this, biopsies are still an important cornerstone in the diagnostic workup of UTUC and in case of endoscopic treatment, the only available histopathology. Currently, conservative treatment of UTUC is increasingly offered to patients with a normal contralateral kidney and low-risk disease. (1) Therefore, knowledge on tumour grade and stage becomes of outmost importance to improve patient selection. Before embracing OCT as a potential test to replace the classical work up, one needs to address the applicability, including time needed for analysis during diagnostic studies and possible limitations of OCT. Recent studies demonstrated high inter-observer agreement for µ oct determination. (15, 16) In addition it is shown that routine µ oct determination for tissue classification does not require extensive training and OCT naïve people only require three trainings to acquire the same results as experienced OCT investigators. (16) Limitations Visual staging of OCT data using our developed protocols is possible during OCT imaging. Large tumors however, are difficult to stage since imaging of OCT is limited to approximately 2 mm in depth. These large lesions can fill up the lumen and do not necessarily show the lay- ered anatomy needed for staging what led to false positives in this study. Inflammation led to a false positive in one patient with isolated CIS in this study. Histopathology showed extended chronical inflammation and fibrosis besides CIS. Previous studies on OCT in blad- der carcinoma have shown that OCT findings in inflammatory state can lead to false posi- tives. Interpretation of OCT findings should be cautious in these settings and the effect of pre-operatively double J-catheter and instillations has to be investigated. (17) For this reason, biopsies will remain necessary to confirm or exclude urothelial cancer in the upper urinary tract. OCT has to be seen as a valuable addition to the diagnostic workup in UTUC and not as a replacement for histology. For example OCT measurement of low-grade recurrence in patients with a prior diagnosis of low-grade, low-stage disease may provide this diag- nosis so that laser fulguration becomes a safer treatment modality and less or no biopsies are necessary. False negatives were seen in two of the six patients with concomitant CIS, in which CIS lesions were not recognized besides tumor lesions. An important limitation of our study protocol was to scan only endoscopic visible lesions, therefore concomitant CIS might have