Case series on clinical applications of liquid biopsy in pediatric solid tumors: towards improved diagnostics and disease monitoring.

Background and aims: Solid tumors account for about 30% of all pediatric cancers. The diagnosis is typically based on histological and molecular analysis of a primary tumor biopsy. Liquid biopsies carry several advantages over conventional tissue biopsy. However, their use for genomic analysis and response monitoring of pediatric solid tumors is still in experimental stages and mostly performed retrospectively without direct impact on patient management. In this case series we discuss six clinical cases of children with a solid tumor for whom a liquid biopsy assay was performed and demonstrate the potential of liquid biopsy for future clinical decision making. Methods: We performed quantitative real-time PCR (RT-qPCR), droplet digital PCR (ddPCR) or reduced representation bisulphite sequencing of cell-free DNA (cfRRBS) on liquid biopsies collected from six pediatric patients with a solid tumor treated between 2017 and 2023 at the Princess Máxima Center for Pediatric Oncology in the Netherlands. Results were used to aid in clinical decision making by contribution to establish a diagnosis, by prognostication and response to therapy monitoring. Results: In three patients cfRRBS helped to establish the diagnosis of a rhabdomyosarcoma, an Ewing sarcoma and a neuroblastoma (case 1-3). In two patients, liquid biopsies were used for prognostication, by MYCN ddPCR in a patient with neuroblastoma and by RT-qPCR testing rhabdomyosarcoma-specific mRNA in bone marrow of a patient with a rhabdomyosarcoma (case 4 and 5). In case 6, mRNA testing demonstrated disease progression and assisted clinical decision making. Conclusion: This case series illustrates the value of liquid biopsy. We further demonstrate and recommend the use of liquid biopsies to be used in conjunction with conventional methods for the determination of metastatic status, prognostication and monitoring of treatment response in patients with pediatric solid tumors.

Microscopically positive resection margin after hepatoblastoma resection: what is the impact on prognosis? A Childhood Liver Tumours Strategy Group (SIOPEL) report.

BACKGROUND: To evaluate the impact of a microscopically positive resection margin (microPRM) on the outcome of hepatoblastoma patients pretreated with chemotherapy. METHODS: Local recurrence and survival rates of 431 children treated in the SIOPEL 2 and 3 trials were analysed comparing 58 patients with microPRM with 371 who had a complete resection (CR) and who were then stratified by risk category. The tumour was standard-risk in 312 patients and high-risk (PRETEXT IV and/or extrahepatic disease and/or α-fetoprotein [AFP]<100 ng/ml) in 117 patients. All received cisplatinum-based neoadjuvant and postoperative chemotherapy as per protocol. Apart from one microPRM patient who went on to transplant, none received any additional local treatment. RESULTS: With a median follow-up of 67 months, local relapse occurred in 3/58 patients with microPRM (5%) and in 23/371 (6%) patients with CR. The 5-year overall survival (OS) was 91% (95% confidence interval [CI] 80%-96%) for the microPRM and 92% (95% CI 89%-95%) for the CR group. The 5-year event-free survival (EFS) was 86% (95% CI 74%-93%) for the microPRM and 86% (95% CI 82%-89%) for the CR group. Neither OS nor EFS was statistically significantly different between the two groups, neither overall nor when risk group stratified. CONCLUSIONS: In the context of cisplatin-based chemotherapy, the presence of microPRM did not influence the outcome even without additional local treatment. Although CR remains the aim, microPRM does not necessitate mandatory second look surgery. A 'wait and see policy' is warranted if postoperative chemotherapy is administered and AFP levels and imaging become normal.

Hepatoblastoma with a low serum alpha-fetoprotein level at diagnosis: the SIOPEL group experience.

AIM OF THE STUDY: To investigate the characteristics of patients with hepatoblastoma and low serum alpha-fetoprotein (AFP) at diagnosis. PATIENTS AND METHODS: Inclusion of all 21 patients accrued onto SIOPEL trials, whose serum AFP was <100ng/ml at diagnosis. Slides of all 15 patients with available histological material were centrally reviewed. RESULTS: Median age: 10 months. Disease extension at diagnosis: PRETEXT group: II (3 patients), III (10 patients) and IV (8 patients). Extra-hepatic extension: 8 patients. Multifocal tumour: 8 patients. Histology at review: wholly epithelial subtype: 11/15 patients including nine with a small-cell undifferentiated histology. OUTCOME: only 9 patients achieved a partial response and 16 died. Median survival: 4.4 months. Two-year overall survival: 24% (confidence interval 10-45%). CONCLUSION: This study clearly identifies patients with hepatoblastoma and low serum AFP at diagnosis as a high-risk subgroup with extensive disease at diagnosis, poor response to chemotherapy and a poor outcome.