Extracranial malignant rhabdoid tumors in children: high mortality even with the help of an aggressive clinical approach.

This paper aims to explore the epidemiology, clinical characteristics, and prognosis of extracranial malignant rhabdoid tumors (eMRTs) in children. A systematic review and meta-analysis of studies published in PUBMED, MEDLINE, Web of Science, Embase, Cochrane, and China National Knowledge Infrastructure (CNKI) was conducted. The search was limited to studies published between Jan 1, 1990 to Dec 31, 2022, with the last search done on Jan 31, 2023. We identified 496 papers through the literature search, and 12 retrospective cohort studies with 398 patients were included. The pooled age at diagnosis for malignant rhabdoid tumor of the kidney (MRTK) was 10.009 months (95%CI (7.542-12.476)), while extracranial malignant rhabdoid tumor (EERT) was 25.917 months (95%CI (17.304-34.530)). Among the 398 patients with eMRTs, chemotherapy treatment rate (86.8% (95%CI (74.4-96.0%))) was more frequently than radiotherapy treatment (45.4% (95%CI (38.1-52.6%))). The rate of metastasis in all patients was 41.4% (95%CI (33.9-48.9%)), in which the lung metastasis was occupied 70.4% (95%CI (58.0-81.6%)). SMARCB1/INI1 mutation was up to 93.2% (95%CI (81.3-99.8%)). The rate of total surgical resection was 50.4% (95%CI (35.2-65.6%)), while pooled proportion of death in all patients was 68.7% (95%CI (56.9-79.5%)).     Conclusion: EMRTs are highly malignant tumors associated with high mortality rates. The loss of SMARCB1/INI1 gene and the protein expression is observed in the vast majority of eMRTs patients. Patients that suffered MRTK are younger than patients with extrarenal EERT and are more prone to lung metastasis, but there is no significant difference in overall survival, possibly due to the higher rate of R0 resection of primary tumors in MRTK.     Trial registration: The study was registered on PROSPERO with registration number CRD42023400985. What is Known: • Malignant rhabdoid tumor (MRT) is a rare and highly malignant tumor that may originate from embryonic stem cells. The incidence of MRT is exceptionally low, estimated at 0.00006%. • Malignant rhabdoid tumor of the kidney (MRTK) and extrarenal extra-cranial malignant rhabdoid tumor (EERT) tend to manifest between 11 to 18 months of age, with a 5-year survival rate of approximately 17%-36%. What is New: • There is no comprehensive meta-analysis or large-scale case series that reported to systematically introduce the eMRTs clinic outcome and prog-nosis based on largely pooled data. • This study performed a meta-analysis through an extensive literature search and clinical data analysis in order to mainly explore the clinical characteris-tics and prognosis of eMRTs, improving the understanding of eMRTs in children..