PURPOSE: We characterized the clinicopathological changes after transarterial chemoembolization for treatment of Wilms tumor. MATERIALS AND METHODS: A total of 44 consecutive patients with Wilms tumor were randomized to undergo transarterial chemoembolization preoperatively or to undergo surgery only. We compared the clinicopathological findings of resected tumor from the 2 groups. RESULTS: Tumor-free survival at 2 years in the group undergoing transarterial chemoembolization was significantly higher compared to the control group (p <0.01), and tumor related recurrence and deaths within 1 year were significantly lower in the study group than in controls (p <0.01). Average tumor shrinkage was 48.2% in the study group. Average area of necrosis in tumor sections was 63.5% in the study group and 15% in controls (AUC 2.78, p <0.01). Percentage of tumor with moderate to severe interstitial fibrosis was 64% (14 of 22 patients) in the study group and 18% (4 of 22) in controls (AUC 2.72, p <0.01). Comparative rates of percentage of tumor demonstrating grade III to IV lymphocytic infiltration were 73% (16 of 22 patients) and 18% (4 of 22, chi-square 11.6, p <0.01), median mitotic index in tissues 1.4 and 0.19 (AUC 55.7, p <0.01), and median apoptotic index of tumor cells 28.1 and 12.8 per 10 microscopic fields (AUC 109.00, p <0.05). Expression of p53 and Bcl-2 protein did not differ between the groups, but Bax protein expression was significantly higher in the study group (85% vs 40%, p <0.05). CONCLUSIONS: Transarterial chemoembolization induces tumor cell necrosis, degeneration and apoptosis, while also boosting interstitial fibrous tissue hyperplasia and lymphocyte infiltration. These histopathological findings could help explain the basis of the better clinical outcome in patients with Wilms tumor who underwent preoperative transarterial chemoembolization.
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