Relationships among slow diffusion coefficient and diffusion-derived 'vessel density' signal features, Gadoxetate delayed enhancement, tumor size, tumor grading, and patient survival: an exploratory study of mass-forming intrahepatic cholangiocarcinoma.

Abstract

Background: Intrahepatic cholangiocarcinoma (ICC) literature suggests that hypervascularity on arterial contrast agent enhancement (CE) is associated with better prognosis, while rich stroma is associated with poorer prognosis. This exploratory study evaluates the relationships among slow diffusion coefficient (SDC) and diffusion-derived 'vessel density' (DDVD) signal features, Gadoxetate delayed enhancement, and survival in patients with mass-forming ICC. An ICC with higher SDC may be associated with potentially better patient survival due to less stromal fibrosis.

Methods: Data were prospectively acquired in two centers [Center 1 (Sun Yat-Sen Memorial Hospital): ICC 21 cases; Center 2 (Fifth Affiliated Hospital of Anhui Medical University): ICC 3 cases]. SDC maps were derived with b=500 and 800 s/mm² images for Center 1 data, and with b=400 and 600 s/mm² images for Center 2 data. DDVD maps were calculated from b=0 and 10 s/mm² images, ADC was calculated from b=0 and 800 s/mm² images (Center 1) or b=0 and 600 s/mm² images (Center 2). Relative to the liver signal, tumor SDC and DDVD signals were assigned to six semi-quantitative score (SQS) categories: low signal (scored as '0'), iso-signal (scored as '1'), slightly high signal (scored as '1.5'), high signal (scored as '2'), higher signal (scored as '2.5'), and markedly high signal (scored as '3'). SDC and ADC were also quantitatively measured. Delayed phase magnetic resonance imaging (MRI) scan was obtained at a median of 3 min 51 sec after the contrast agent injection. Percentage area of CE during delayed phase ('% delay CE') was estimated visually and also quantified with the spleen CE signal intensity as the reference. Follow-up data were available in 20 cases from Center 1 (n=9 alive till the last follow-up, n=11 died during the follow-up), and we conducted additional histopathological grading for 14 cases from Center 1.

Results: Tumor aggressiveness was negatively correlated with quantitative '% delay CE' (Spearman r_s =0.703, P=0.008). Based on visual assessment, both SDC SQS and DDVD SQS were moderately and positively correlated with '% delay CE', with a Spearman r_s of 0.504 (P=0.02) and 0.549 (P=0.03), respectively. Correlation of quantitative '% delay CE' with relative threshold of spleen CE signal intensity and ln(SDC_ICC/SDC_liver) derived a Pearson r of 0.481 (P=0.03). The alive group (n=9) had a SDC SQS higher than the dead group (n=11, mean: 2.89 vs. 2.23, P=0.007). The dead group had 4 cases with SDC SQS ≥2.5, three of them had tumor sizes >4,000 mm², and an additional patient had an advanced age of 76 years.

Conclusions: ICCs with higher SDC score (≥2.5) and small/intermediate presenting tumor size (<4,000 cm² in the largest section) are associated with better survival potential. ICCs with lower SDC score (≤2.0) are likely associated with a poor prognosis.