Analysis on diagnosis and treatments of 16 cases of extracranial malignant rhabdoid tumor in children.

Background: To explore the clinical features, treatment and early prognosis of malignant rhabdoid tumor (MRT) of kidney and extrarenal extracranial soft tissue in children.

Methods: From January 2011 to July 2021, a total of 16 patients, who were diagnosed with MRTs of the kidney and extrarenal soft tissue were retrospectively analyzed and were divided into MRT of the kidney (MRTK) and extrarenal extracranial MRT (EERT).

Results: Sixteen patients were followed up for at least 15 months. The overall average age of onset was (26.6±20.1 months), the 1-year overall survival (OS) of 71.4% at the age of ≥24 months was significantly higher than the 1-year OS (11.1%) <24 months of age [hazard ratio (HR) =0.21 (0.06-0.77), log-rank P=0.019<0.05]. The distant metastasis rate of children in the MRTK group (83.3%) is significantly higher than EERT group (20%) (P=0.017<0.05), and the proportion of children with lung metastasis in the MRTK group was as much as 83.3%, which was significantly higher than that in the EERT group (10%) (P<0.05), but the related metastases and primary tumors did not regress after radiotherapy and chemotherapy in all cases. In the MRTK group, 5 cases were completely excised, but only 1 survived; while 5 cases in the EERT group that were completely excised and all alive. Children with tumor total excision in EERT group had a 1-year OS of 100% as compared to children with tumor total excision in MRTK group had a 1-year OS of 20% [HR =0.07 (0.01-0.57), log-rank P=0.013<0.05]. The average survival time of dead cases in MRTK group and EERT group were 6.60±3.28 months and 1.40±0.65 months respectively (P=0.008<0.05).

Conclusions: Children with MRT under 2 years of age have significantly worse prognosis than children exceeding 2 years of age. MRTK is more prone to lung metastasis but has longer survival time, which is related to the R0 resection of the primary tumor. Children with EERT may have a better prognosis if the tumor can be completely resected with the impact of age. MRTK and EERT are both insensitive to radiotherapy and chemotherapy.