Introduction: Clear cell sarcoma of the kidney (CCSK) is a rare malignant childhood
renal tumour. Recently, the central nervous system (CNS) was found to be the most
frequent site of relapse associated with a poor outcome. Optimal treatment strategies
are scarce.
Patients and Methods: Retrospective data analysis of all Austrian children with CCSK.
They were enrolled in the Austrian-Hungarian Wilms Tumour Study (AHWTS) 1989,
the SIOP93-01 or the SIOP2001 study between 1990 and 2019. Demographic, diagnostic, treatment-related variables and survival data were analysed.
Results: We identified 12 children with CCSK (M = 7, F = 5; median age 1.6 years). All
had localised disease (stage I: 2; stage II: 2; stage III: 8) at diagnosis, and a first complete
remission (CR1) was achieved in 12/12. Six patients are in an ongoing CR1 (median
follow-up 10 years). Six other patients had a relapse (local 1; brain 5) a median time of
2.4 years from diagnosis. Two patients died of the disease 4 months and 2.8 years after
first relapse. Four of five patients with CNS relapse are in CR2 with a median followup time of 9.3 years after relapse diagnosis. Relapse treatment included a combination
of chemotherapy, radiation and surgery. Two children received high-dose chemotherapy followed by autologous stem cell rescue, and one child received intrathecal mafosphamide. Long-term side effects after treatment were impaired tubular renal function
(n = 4), cardiomyopathy (n = 1) and growth disorders (n = 1).
Conclusions: In this series, the brain was the most common site of relapse. Long-term
survival after recurrence was achievable with intensive multimodal therapy
