Seppo Taskinen, Outi Leskinen, Minna Koskenvuo, Jouko Lohi, Mervi Taskinen
Purpose. To evaluate if Wilms tumor histopathology predicts occurrence of pulmonary metastases and the response of lung metastases to neoadjuvant chemotherapy. Methods. Seventy-nine patients under age 16 years were identified with Wilms tumor in 1988 – 2015. All thoracic CT-images before and after neoadjuvant chemotherapy with suspected metastases were re-evaluated. Tumor volumes were measured from CT- or MRI-images (available in 52/79 patients). Tumor samples from both pre-treatment cutting needle biopsies (CNB) and from nephrectomy were re-evaluated (59/79). Results. Pulmonary metastases were found in 14 out of 79 (18%) patients. Patients with pulmonary metastases had larger Wilms tumor volume (903, IQR 807-1215 ml vs. 428, IQR 299-765 ml; p<0.001), and tended to have predominance of blastemal cells in diagnostic CNB (75, QR 50-97% vs. 50, IQR 20-80%; p=0.064) compared to those without pulmonary metastases. At nephrectomy samples, the proportion of necrosis was higher in patients with metastases (95,IQR76-99% vs. 60IQR 20-96%; p=0.026). In six cases (43%) the pulmonary metastases disappeared with neoadjuvant treatment. Disappearance of metastases was not associated with original renal tumor volume or tumor shrinking or final tumor histology. However, blastemal cell content at diagnosis was larger in the cases with persisting metastases (85% (IQR 73-94) vs. 50% (IQR 30-50), p=0.027). Conclusions. Pulmonary metastases are more common in children with a large Wilms tumor especially when the proportion of blastemal cells is high. Half of the pulmonary metastases disappeared during the preoperative chemotherapy. Large blastemal cell content at diagnosis was associated with persisting metastases.