Ultrasound-Guided Percutaneous Ethanol-Paclitaxel Combined Therapy for Rabbit VX2 Liver Tumors

Abstract

Background: It is difficult to achieve whole tumor ablation using percutaneous ethanol ablation therapy (PEAT) due to the limited diffusion of ethanol.

Purpose: To determine whether chemotherapy can be an adjuvant therapy to benefit PEAT, we investigated ultrasound-guided percutaneous ethanol-paclitaxel combined therapy (PEPCT) of VX2 carcinoma, a rabbit liver cancer model.

Materials and methods: A six-arm study was designed to quantify the correlation between paclitaxel (PTX) dose and tumor necrosis or cell proliferation, including sham group (2 mL saline, n=6), incremented dose of PTX (0, 12.5, 25, 37.5 mg) in 2.0 mL ethanol (n=6) and a conventional PEAT group (n=6) as comparison. The test was followed by contrast-enhanced ultrasonic (CEUS) before 7-day sacrifice, tumor harvest, and sectioning. Tumor necrosis ratio was radiologically and histologically quantified; modified proliferation index (m-PI) was proposed to quantify the PTX's pharmacological effects. A linear regression model was set to correlate the PTX dose with tumor necrosis ratio or cell proliferation index. The difference of radiological, histological necrosis ratio (HNR) and modified PI in six groups was analyzed via Kruskal-Wallis H-test, Welch analysis of variance and one-way ANOVA.

Results: Incremental increases of PTX (0, 12.5, 25, 37.5 mg) correlated with greater fraction of tumor necrosis (R² = 0.946, P<0.001 for radiological necrosis ratio [RNR], R² = 0.843, P<0.001 forHNR), indicating that one week after procedure PTX's anti-proliferation and ethanol's dehydration co-induced severe tumor necrosis. Correlation analysis further testified a significant association between PTX dose and m-PI (R² = 0.860, P<0.001).

Conclusion: These results suggest a clear role for PTX-induced cytotoxicity and support the use of chemotherapeutic drugs in ablation therapy.

Keywords: PEAT; PTX; VX2 liver cancer model; combined therapy; new indication; paclitaxel; percutaneous ethanol ablation therapy.

Figure 1

(A) Scheme of the PEPCT technique: The infusion needle is punctured percutaneously into the lesion under the guidance of ultrasound imaging. The half volume of ethanol is injected into 1/3 point, the other half at 2/3 point. (B) Organizational chart of the study design, consisting of four treatment arms with the PTX varying in the dose in ethanol solvent and conventional PEA (C-PEA).

Figure 2

A typical cut surface photograph of the resected specimen of VX2 tumors. Generally, the white area is considered as viable tumor residue. In the saline group (group 1), the whole tumor looks highly viable. Ablation or synergistic ablation-chemotherapy treatment caused necrosis at different levels, Extremely, at the highest dose of PTX (group 6), the VX2 tumor is almost completely necrotic.

Figure 3

(A) The RNR values in all six groups were determined by the enhanced area recorded at the arterial phase of CEUS measured at one week after the procedure. (B) HNR values in all six groups were determined by automatically reading the H&E slices.

Figure 4

Scatterplot of PTX dose versus percentage tumor necrosis ratio with a best-fit regression line shows a strong linear relationship between these parameters. The slope indicated a dose dependent response: the necrosis ratio increases radiologically (A) by 1.721%/mg (95% CI:1.535–1.907) and histologically (B) by 1.14%/mg (95% CI:0.92–1.35), respectively.

Figure 5

(A) Typical photographs for m-PI measured. Red asterisks represent the viable, and well-proliferated (Ki-67 positive) cells. Scale bar at the low magnification (10×):100 µm; at the high magnification (40×): 30 µm. (B) Individual m-PI values. (C) Scatterplot of PTX dose versus m-PI.