Unresectable hepatocellular carcinoma: serial early vascular and cellular changes after transarterial chemoembolization as detected with MR imaging

Abstract

Purpose: To prospectively assess serial changes in contrast material-enhanced and diffusion-weighted (DW) magnetic resonance (MR) imaging values within 1 month after transarterial chemoembolization (TACE) in patients with unresectable hepatocellular carcinoma (HCC).

Materials and methods: Institutional review board approval was obtained for this prospective HIPAA-compliant study. MR imaging was performed before and within 24 hours after TACE in 24 patients with HCC (21 male, three female; mean age, 59 years and 62 years, respectively). Serial MR imaging was subsequently performed 1, 2, 3, and 4 weeks after therapy. The imaging protocol included fast spin-echo T2-weighted MR imaging, breath-hold DW echo-planar MR imaging, and breath-hold unenhanced and contrast-enhanced T1-weighted three-dimensional fat-suppressed gradient-recalled-echo MR imaging in the arterial and portal venous phases. Tumor size, enhancement, and apparent diffusion coefficient (ADC) values were recorded before and sequentially after treatment. Regression models for the correlated data were used to assess changes in these parameters over time after TACE.

Results: Mean tumor size was 7.5 cm and was unchanged up to 4 weeks after therapy. Reduction in tumor enhancement in the arterial phase occurred immediately after TACE, with a consistent reduction occurring 1-3 weeks after therapy (P = .001). Reduction in tumor enhancement in the portal venous phase also occurred immediately after TACE, with a consistent reduction occurring 1-3 weeks after therapy (P = .0003). The increase in tumor ADC value was significant 1-2 weeks after therapy (P = .004), borderline significant 3 weeks after therapy, and insignificant 24 hours and 4 weeks after therapy.

Conclusion: Significant reduction in tumor enhancement occurred within 24 hours after TACE and persisted up to 4 weeks after TACE. Lesser changes in the ADC value appeared 1 week after TACE, persisted through 2 weeks after TACE, and became less apparent 3 and 4 weeks after TACE. No change in tumor size was recorded during the follow-up period.

Figure 1:

A–E, Serial changes in gadolinium enhancement of a mass (arrow) on subtracted T1-weighted gadolinium-enhanced portal venous phase images (left: 5.1/1.2), DW MR images (middle: 6500/110), and ADC images (right) after TACE. A, Baseline images. Left: A 2.5-cm mass in left lobe shows almost complete (100%) enhancement. Middle: Hyperintense mass is visible. Right: ADC = 0.00172 mm²/sec. B, At 24 hours after TACE. Left: Mass shows significant enhancement reduction (−50%). Middle: Mass is isointense. Right: ADC = 0.00180 mm²/sec. C, At 1 week after TACE. Left: Mass shows no enhancement. Middle: Mass is isointense. Right: ADC = 0.00203 mm²/sec. D, Left: At 2 weeks after TACE. Mass shows no enhancement. Middle: Mass is isointense (arrow). Right: ADC = 0.00210 mm²/sec. E, At 4 weeks after TACE. Left: Mass shows no enhancement. Middle: Mass is isointense (arrow). ADC = 0.00179 mm²/sec. Tumor remains unchanged in size.

Figure 2:

Box plots show serial changes in ADC values (black boxes) and arterial (red boxes) and portal venous (blue boxes) enhancement. The length of the box is the interquartile range of data and indicates the spread of the middle 50% of the observations. The median is indicated by the horizontal line inside the box.