The role of pre-operative ctDNA in resectable intrahepatic cholangiocarcinoma.

Abstract

528 Background: Genomic profiling of circulating tumor DNA (ctDNA) is increasingly used in intrahepatic cholangiocarcinoma (iCCA) to inform precision oncology approaches and determine resistance mechanisms to targeted therapies. The application of pre-operative ctDNA testing in the management of iCCA for prognostication remains unclear. Methods: In this retrospective study, we analyzed pre-operative plasma samples from 14 patients who underwent curative resection for iCCA without neoadjuvant therapy. A personalized and tumor-informed assay (Signatera; Natera, Inc.) was used for the detection and quantification of ctDNA. We correlated ctDNA profiles with baseline tumour characteristics and clinical outcomes. Results: The mean interval between pre-operative blood collection and surgery was 43 days (range: 1 to 90 days). ctDNA was detected in all patients except for one with stage Ia (AJCC 8th) disease (Table). The mean pre-operative ctDNA concentration was lowest in the stage Ia group [4.2 mean tumor molecules (MTM)/mL] and highest in the stage II group (134.0 MTM/mL). The mean pre-operative ctDNA concentration did not exhibit a linear correlation with disease recurrence or mortality rates, however, it showed a moderate-to-good linear correlation with the largest pathologic tumor size (R2 = 0.55). Among the three patients who had IDH1/2 mutations tracked in the plasma by Signatera, two patients had positive IDH1/2 detection in ctDNA with mean ctDNA concentrations of 83.7 MTM/mL (range: 33.8 to 133.5 MTM/mL). The patient with the second-highest ctDNA concentration (133.5 MTM/mL and 1818 days follow-up) had stage Ib disease with an IDH1 mutation but has shown no evidence of recurrence. Conclusions: In the pre-operative setting for iCCA resections, ctDNA can be reliably detected across all disease stages using a tumor-informed approach, even when blood is collected up to 90 days before surgery. While single time-point pre-operative ctDNA concentration levels do not appear to correlate with outcomes, similar to previous reports in colon adenocarcinoma, they may correlate with tumor volume. Further studies are needed to evaluate the utility of tumor-informed ctDNA testing in the post-operative setting to detect molecular residual disease for improved prognostication. [Table: see text]