Clinical and genetic risk factors define two risk groups of extracranial malignant rhabdoid tumours (eMRT/RTK)

INTRODUCTION

Extracranial rhabdoid tumours are rare, highly aggressive malignancies primarily affecting young children. The EU-RHAB registry was initiated in 2009 to prospectively collect data of rhabdoid tumour patients treated according to the EU-RHAB therapeutic framework.

METHODS

We evaluated 100 patients recruited within EU-RHAB (2009-2018). Tumours and matching blood samples were examined for SMARCB1 mutations by sequencing and cytogenetics.

RESULTS

A total of 70 patients presented with extracranial, extrarenal tumours (eMRT) and 30 with renal rhabdoid tumours (RTK). Nine patients demonstrated synchronous tumours. Distant metastases at diagnosis (M+) were present in 35% (35/100), localised disease (M0) with (LN+) and without (LN-) loco-regional lymph node involvement in 65% (65/100). SMARCB1 germline mutations (GLM) were detected in 21% (17/81 evaluable) of patients. The 5-year overall survival (OS) and event-free survival (EFS) rates were 45.8 ± 5.4% and 35.2 ± 5.1%, respectively. On univariate analyses, age at diagnosis (≥12 months), M0-stage, absence of synchronous tumours, absence of a GLM, gross total resection (GTR), radiotherapy and achieving a CR were significantly associated with favourable outcomes. In an adjusted multivariate model presence of a GLM, M+ and lack of a GTR were the strongest significant negative predictors of outcome.

CONCLUSIONS

We suggest to stratify patients with localised disease (M0), GTR+ and without proof of a GLM (5-year OS 72.2 ± 9.9%) as 'standard risk'. Patients presenting with one of the features M+ and/or GTR- and/or GLM+ belong to a high risk group (5-year, OS 32.5 ± 6.2%). These patients need novel therapeutic strategies such as combinations of targeted agents with conventional chemotherapy or novel experimental approaches ideally within international phase I/II trials.

Malignant rhabdoid tumor of the liver presented with initial tumor rupture

Malignant rhabdoid tumor (MRT) of the liver is a rare, highly aggressive tumor of early childhood. We report a 6-month-old boy who was diagnosed with MRT of the liver and presented with spontaneous tumor rupture. The patient underwent intensified chemotherapy and a radical surgical procedure. Twenty four months from the time of the diagnosis, he is alive without evidence of disease. This is the second report of prolonged survival after initial rupture of hepatic MRT.

NFB-13. Rhabdoid Tumor Predisposition Syndrome (RTPS) – Finding Evidence by systematic Analyses

BACKGROUND: Individuals with rhabdoid tumor predisposition syndrome (RTPS1 – SMARCB1, RTPS2 – SMARCA4) have a propensity to develop malignant rhabdoid tumors (MRT). Affected patients typically present < age 12 months with synchronous tumors (SYN) exhibiting an unusually aggressive clinical behavior. Due to the rarity of RTPS, standards for management are evolving. METHODS: Clinical, genetic, and treatment data of 90 patients with RTPS from 16 countries were analyzed (2004 – 2020). Therapy followed the EU-RHAB recommendations. Tumors and matching blood samples were investigated for SMARCB1 and/or SMARCA4 mutations using FISH, MLPA and sequencing. DNA-methylation subgroups were determined using DNA methylation arrays. RESULTS: The median age at diagnosis of 52 girls and 38 boys was 5.5 months (0 – 203). 55.5% (50/90) of patients presented with an atypical teratoid/rhabdoid tumor (ATRT), 23.5% (21/90) demonstrated SYN, and 21% (19/90) extracranial MRT. RTPS1 was present in 84-, RTPS2 in six patients. In 77% (65/84) complete data on SMARCB1 mutational status were generated. Methylation subgroup status was available in 59% (40/68) of ATRT or SYN. The 5-year overall- (OS) and event free survival rates of patients with RTPS1 were 19.8 ± 4.8% and 15 ± 4.2%, respectively. Age < 1 year at diagnosis (10.1±4.3% vs. 46.7±11.1%), presence of SYN (5.3±5.1% vs. 24.8±6%), histological diagnosis (ATRT vs. eMRT/RTK/SYN) (26.8±7.1% vs. 11.9±5.6%), localized disease (34.5±8 vs. 8.3±4.6%), and presence of PGV at C-terminal (33±8.6% vs. 9.4±5.3%) were significant prognostic factors for 5-year OS in univariate analysis. INTERPRETATION: In the largest cohort of patients with RTPS, predictors significant for positive outcome could be detected: age > 1 year, absence of SYN, histological diagnosis ATRT, localized disease and PGV located at C-terminal. In our research project, we aim to characterize the complete pheno- and genotype of patients with RTPS to develop a risk score including surveillance recommendation.

ATRT-05. Infants and newborns with atypical teratoid/rhabdoid tumors (ATRT) and extracranial malignant rhabdoid tumors: a unique and challenging population

INTRODUCTION: Malignant rhabdoid tumors (MRT) predominantly affect infants. Patients below six months represent a particularly challenging group: intensity of therapy is limited by toxicity to developing organs. Information on prognostic factors, toxicity and long term outcome is sparse. METHODS: Clinical, genetic, and treatment data of 100 patients (less than 6 months at diagnosis) from 13 European countries were analyzed (2005-2020). Tumors and matching blood samples were examined for SMARCB1 mutations using FISH, MLPA and Sanger sequencing. DNA-methylation subgroups (ATRT-TYR, ATRT-SHH, and ATRT-MYC) were determined using DNA methylation arrays. RESULTS: A total of 45 patients presented with ATRT, 29 with extracranial, extrarenal (eMRT) and 9 with renal rhabdoid tumors (RTK). Seventeen patients demonstrated synchronous tumors (SYN). Distant metastases at diagnosis (M+) were present in 27% (26/97). A germline mutation (GLM) was detected in 55% (47/86). Methylation subgroup status was available in 50% (31/62) of ATRT or SYN (SHH=13, TYR=13, MYC=4, SHH+TYR=1). The 5-year overall- (OS) and event free survival (EFS) rates were 23.5±4.6% and 19±4.1%, respectively. Male sex (11±5% vs. 35.8±7.4%), M+ (6.1±5.4% vs. 36.2±7.4%), presence of SYN (7.1±6.9% vs. 26.6±5.3%) and -GLM (7.7±4.2% vs. 45.7±8.6%) were significant prognosticators of 5-year OS, in univariate analysis. Molecular subgroup and survival analyses confirmed the previously described survival advantage of ATRT-TYR. In an adjusted multivariate model clinical factors that influence prognosis were: male sex [HR: 2.1 (1.2 – 3.6)], M+ [3.3 (1.8 – 6)], GLM [HR: 2 (1.1 – 3.6)] and maintenance therapy [HR: 0.3 (0.1 – 0.8)]. CONCLUSION: In this large cohort of homogenously treated infants with MRT, significant predictors of outcome were sex, M+, GLM and maintenance therapy. We confirm the need to stratify which patient group benefits from multimodal treatment, and which patients need novel therapeutic strategies. Biomarker-driven tailored trials may be a key option.