[Analysis of 18 cases of malignant rhabdoid tumor in children]

Objective: To investigate the clinical characteristics, treatment and prognosis of malignant rhabdoid tumor (MRT) in children. Methods: Clinical data total of 18 children with MRT treated in the Department of Hematology and Oncology, Children's Hospital, the First Affiliated Hospital of Zhengzhou University between June 2015 to June 2021 were analyzed retrospectively. The patients were grouped according to age, gender, tumor type, clinical stage and other factors.Progression free survival (PFS) and overall survival (OS) were calculated by Kaplan-Meier method, survival differences among different groups were compared by Log-rank test, and prognostic factors were analyzed by Cox regression model. Results: Among the 18 patients, there were 5 males and 13 females. The age of disease onset was 30.5 (12.0, 75.0) months, the tumor diameter was (80±29) mm, and no integrase interactor 1 (INI-1) expression was detected by immunohistochemistry. There were 7 cases of malignant rhabdoid tumor of the kidney (MRTK), 6 cases of atypical teratoid rhabdoid tumor (ATRT) and 5 cases of extrarenal extracranial rhabdoid tumor (EERT). At the time of early diagnosis, 12 patients were clinically stage Ⅲ-Ⅳ, 11 patients had local or distant metastasis, and 4 patients had metastasis during treatment. Surgical excision is the preferred treatment. There were 3 cases with preoperative puncture biopsy, 13 cases with complete resection, 4 cases with partial resection, and 1 case without operation. Thirteen patients were treated with the domestic conventional chemotherapy regimen for Wilms' tumor, medulloblastoma and rhabdomyosarcoma, and 5 patients were treated with the international conventional chemotherapy regimen. Nine patients received radiotherapy, including 1 case of MRTK, 4 cases of ATRT and 4 cases of EERT. By the end of follow-up in January 2022, 7 patients survived and 11 patients died. The 3-year PFS and OS rates were (8±8) % and (14±12) %. Log-rank test showed that the 5-year OS of EERT group was higher than ATRT and MRTK groups (χ²=16.31, P<0.001), the tumor diameter <80 mm group was higher than that of the ≥80 mm group (χ²=4.49, P=0.034), and the radiotherapy group was higher than no radiotherapy group (χ²=3.97, P=0.046). The differences were statistically significant. There was no significant difference in the influence of tumor type, age, tumor diameter, radiotherapy and chemotherapy on OS by Cox regression model (all P>0.05). Log-rank test showed that the 3-year PFS of EERT group was higher than ATRT and MRTK groups (χ²=11.14, P=0.004),>3 years group was higher than ≤3 years group (χ²=10.10, P=0.001), the differences were statistically significant. Tumor type, clinical stage, tumor diameter, age, tumor rupture and radiotherapy were included in the Cox regression model, and the results showed that clinical stage (HR=0.49, 95%CI 0.26-0.94, P=0.031), tumor diameter (HR=8.67, 95%CI 1.84-40.89, P=0.006), age (HR=0.01, 95%CI 0.00-0.15, P=0.001) had statistical significance on PFS. Conclusions: MRT is one of the most aggressive and fatal cancers in early childhood and infancy. There is no standard treatment and the prognosis is extremely poor. Clinical stage, tumor size and age are risk factors for disease progression.