Magnetic Resonance Imaging in Objective Response Evaluation in Klatskin Tumor Patients after Endobiliary Photodynamic Therapy

Abstract

Purpose: Visualization of periductal infiltrative hilar cholangiocarcinomas in general and their changes in response to endobiliary photodynamic therapy (PDT) in particular is not an easy diagnostic task because of their small size, infiltrative growth pattern, and absence of clearly circumscribed margins with adjacent tissue. This caused most researchers to give up the study of criteria for objective response to locoregional treatment, and to use only the survival rate as performance criteria. The aim of this study is to determine the criteria of objective response in Klatskin tumor after PDT based on the analysis of preand postoperative MRI.Material and methods: The study covered 42 patients (26 male (62 %) and 16 female (38 %)) with morphologically verified Klatskin tumor aged 21-76 (median 55) after 104 sessions (from 1 to 10, median 2) of percutaneous endobiliary PDT over the period of 2007-2020. All patients had percutaneous transhepatic or intraoperative drainage of bile ducts from 1 week to 2 years before PDT. Chlorine photosensitizers were used for PDT. The LAHTA-MILON programmable laser unit with 662 nm wavelength was used for photo-irradiation. The specific dose varied from 4.6 to 232,2 J/cm2 (median 29) and the total dose was 64.6-3890 J (median 950), depending on the extent of lesion and the patient’s tolerance to interventions. 220 abdominal MRI were done at various times before and after PDT. Preoperative MRI were completed 1-101 days (median 13.5 days) before the intervention. Postoperative MRI scans were split into groups based on the time following the intervention: 1) after 1–5 days, 2) after 2 months, 3) after 3 months, and 4) after 4 months. Examinations were carried out with the Siemens Magnetom Avanto/Espree 1.5 Tesla MRI scanner. To compare the indicators at different times, the Kruskal–Wallis test was used, p < 0.05 were considered significant.Results: As a result of the analysis, the following statistically significant changes in the Klatskin tumor after PDT were obtained at various times: the largest transverse size of the tumor infiltrate decrease at the proximal hepaticocholedochus level 1 month after PDT; the infiltrate longitudinal size increase at the bile ducts confluence level 4 month after PDT; T2-WI signal intensity increase at the photodynamic area in 1–5 days after PDT; T1-WI signal intensity decrease in various contrasting phases at the photodynamic area in 1–5 days after PDT; ADC signal intensity increase at the photodynamic and conditionally healthy tissues areas 1 month after PDT; T1-WI signal intensity increase in venous and delayed contrasting phases at the photodynamic area 1 month after PDT; T1-WI signal intensity decrease in porto-venous and delayed contrasting phases at the photodynamic area 2 month after PDT; ADC signal intensity decrease at conditionally healthy tissues 4 month after PDT.Conclusion: Changes in MR signal intensity after endobiliary PDT with different pulse sequences (DWI + ADC, T2-WI with and without suppression of signal from adipose tissue, T1-WI before and after intravenous injection of contrast agent in 4 phases of contrasting) in pathological and conditionally healthy intraand periductal tissues and the tumor dimensions (largest crosssectional dimensions and thickness measured in axial and coronal projections in T2-WI) may be used as the criteria of objective response. Determination in the early postoperative period of periductal segments in the area of photodynamic treatment that do not accumulate contrast agent is the most informative, displayable and convenient for practical use criterion of objective response indicating the ischemia of tumor tissue.