Hallmark discoveries in the biology of Wilms tumour.

The modern study of Wilms tumour was prompted nearly 50 years ago, when Alfred Knudson proposed the 'two-hit' model of tumour development. Since then, the efforts of researchers worldwide have substantially expanded our knowledge of Wilms tumour biology, including major advances in genetics - from cloning the first Wilms tumour gene to high-throughput studies that have revealed the genetic landscape of this tumour. These discoveries improve understanding of the embryonal origin of Wilms tumour, familial occurrences and associated syndromic conditions. Many efforts have been made to find and clinically apply prognostic biomarkers to Wilms tumour, for which outcomes are generally favourable, but treatment of some affected individuals remains challenging. Challenges are also posed by the intratumoural heterogeneity of biomarkers. Furthermore, preclinical models of Wilms tumour, from cell lines to organoid cultures, have evolved. Despite these many achievements, much still remains to be discovered: further molecular understanding of relapse in Wilms tumour and of the multiple origins of bilateral Wilms tumour are two examples of areas under active investigation. International collaboration, especially when large tumour series are required to obtain robust data, will help to answer some of the remaining unresolved questions.

Tumor biology, biomarkers, and liquid biopsy in pediatric renal tumors.

The expansion of knowledge regarding driver mutations for Wilms tumor (WT) and malignant rhabdoid tumor of the kidney (MRT) and various translocations for other pediatric renal tumors opens up new possibilities for diagnosis and treatment. In addition, there are growing data surrounding prognostic factors that can be used to stratify WT treatment to improve outcomes. Here, we review the molecular landscape of WT and other pediatric renal tumors as well as WT prognostic factors. We also review incorporation of circulating tumor DNA/liquid biopsies to leverage this molecular landscape, with potential use in the future for distinguishing renal tumors at the time of diagnosis and elucidating intratumor heterogeneity, which is not well evaluated with standard biopsies. Incorporation of liquid biopsies will require longitudinal collection of multiple biospecimens. Further preclinical research, identification and validation of biomarkers, molecular studies, and data sharing among investigators are crucial to inform therapeutic strategies that improve patient outcomes.

White paper: Oncofertility in pediatric patients with Wilms tumor.

The survival of childhood Wilms tumor is currently around 90%, with many survivors reaching reproductive age. Chemotherapy and radiotherapy are established risk factors for gonadal damage and are used in both COG and SIOP Wilms tumor treatment protocols. The risk of infertility in Wilms tumor patients is low but increases with intensification of treatment including the use of alkylating agents, whole abdominal radiation or radiotherapy to the pelvis. Both COG and SIOP protocols aim to limit the use of gonadotoxic treatment, but unfortunately this cannot be avoided in all patients. Infertility is considered one of the most important late effects of childhood cancer treatment by patients and their families. Thus, timely discussion of gonadal damage risk and fertility preservation options is important. Additionally, irrespective of the choice for preservation, consultation with a fertility preservation (FP) team is associated with decreased patient and family regret and better quality of life. Current guidelines recommend early discussion of the impact of therapy on potential fertility. Since most patients with Wilms tumors are prepubertal, potential FP methods for this group are still considered experimental. There are no proven methods for FP for prepubertal males (testicular biopsy for cryopreservation is experimental), and there is just a single option for prepubertal females (ovarian tissue cryopreservation), posing both technical and ethical challenges. Identification of genetic markers of susceptibility to gonadotoxic therapy may help to stratify patient risk of gonadal damage and identify patients most likely to benefit from FP methods.

Unmet needs for relapsed or refractory Wilms tumour: Mapping the molecular features, exploring organoids and designing early phase trials - A collaborative SIOP-RTSG, COG and ITCC session at the first SIOPE meeting.

Wilms tumour (WT) accounts for about 6% of all childhood cancers and overall survival of WT is about 90% in international protocols. However, for WT subgroups with much poorer prognoses, i.e. typically high-risk (unfavorable) histology and/or relapse, there is an unmet need to better understand the biology of WT and to translate biological findings into clinics through early phase clinical trials that evaluate innovative therapies. The main challenges are the small numbers of children suitable for early phase trials, the genetic heterogeneity of WT and the low number of somatic mutations that are currently considered 'druggable'. Accordingly, a joint meeting between clinical and biology experts from the international cooperative groups of the Renal Tumour Study Group of the International Society of Paediatric Oncology, the Renal Tumour Committee of the Children's Oncology Group and the European Innovative Therapies for Children with Cancer consortium and parents representatives was organised during the first SIOPE meeting in Prague, 2019. We reviewed WT molecular features, ongoing/planned early phase trials and explored available knowledge on organoid technology. The key messages were: (1) relapsed WT should undergo whenever possible thorough molecular characterization and be enrolled in protocols or trials with systematic data collecting and reporting; (2) WT displays few known 'actionable' targets and currently no novel agent has appeared promising; (3) we need to improve the enrolment rate of WT candidates in early phase trials especially for the relatively small subgroup of relapses with an adverse prognostic signature; (4) despite some agnostic early phase trials existing, development of WT-focused trials are warranted; (5) growing organoids with parallel testing of drug panels seems feasible and may direct individual treatment and encourage clinical researchers to incorporate the most promising agents into early phase trials.

Novel therapy for pediatric and adolescent kidney cancer.

Pediatric and adolescent renal tumors account for approximately 7% of all new cancer diagnoses in the USA each year. The prognosis and treatment are varied based on factors including the underlying histology and tumor stage, with survival rates ranging from greater than 90% in favorable histology Wilms tumor to almost universally fatal in other disease types, including those patients with advanced stage malignant rhabdoid tumor and renal medullary carcinoma. In recent years, our understanding of the underlying genetic drivers of the different types of pediatric kidney cancer has dramatically increased, opening the door to utilization of new targeted biologic agents alone or in combination with conventional chemotherapy to improve outcomes. Several ongoing clinical trials are investigating the use of a variety of targeted agents in pediatric patients with underlying genetic aberrations. In this manuscript, the underlying biology and early phase clinical trials relevant to pediatric renal cancers are reviewed.

Testicular wedge biopsy for fertility preservation in children at significant risk for azoospermia after gonadotoxic therapy.

BACKGROUND/PURPOSE: Testicular tissue cryopreservation (TTC) provides an experimental option for fertility preservation for male children at significant risk for azoospermia owing to high-risk gonadotoxic treatments. METHODS: A single institution, retrospective review of TTC cases from 2015 to 2017. Children at significant risk for azoospermia were eligible for study inclusion. A unilateral wedge biopsy of the testis was performed for TTC. RESULTS: TTC was performed in 23 patients. Average age was 10 years old (5 months to 18 years). Diagnoses included solid tumor (74%, n = 17), hematologic malignancy (17%, n = 4), and benign hematologic disease (13%, n = 3). Six patients had TTC at the time of disease relapse. Nine patients were referred for TTC prior to stem cell transplantation. The majority (70%, n = 16) of patients had an additional procedure at the time of TTC. One patient developed postoperative scrotal cellulitis that was treated with antibiotics. The majority of patients (96%, n = 22) had normal testicular tissue with the presence of germ cells on histopathological analysis. Median time to start of medical therapy was seven days with no unanticipated treatment delays. CONCLUSIONS: Testicular wedge biopsy for TTC can be performed safely, coordinated with other necessary procedures, and does not delay the start of treatment. TTC remains an experimental option for fertility preservation for children, as no spermatogenic recovery or pregnancies from cryopreserved testicular tissues have been reported to date. LEVEL OF EVIDENCE: IV.

Laparoscopic unilateral oophorectomy for ovarian tissue cryopreservation in children.

BACKGROUND/PURPOSE: Many survivors of childhood cancer will experience premature gonadal insufficiency or infertility as a consequence of their medical treatments. Ovarian tissue cryopreservation (OTC) remains an experimental means of fertility preservation with few reports focused on the surgical technique and postoperative outcomes for OTC in children. METHODS: This is a single institution, retrospective review of OTC cases from January 2011 to December 2017. Children were eligible for OTC if they had a greater than 80% risk of premature ovarian insufficiency or infertility owing to their anticipated gonadotoxic medical treatment. RESULTS: OTC was performed in 64 patients. Median age was 12 years old (range: 5 months-23 years). Nearly half (48%) of the patients were premenarchal. Laparoscopic unilateral oophorectomy was performed in 84% of patients. There were no surgical complications. In 76% of patients, OTC was performed in conjunction with an ancillary procedure. The majority (96%) of patients were discharged within 24 hours. Median time from operation to medical therapy was six days, with no unanticipated treatments delays attributable to OTC. CONCLUSIONS: Laparoscopic unilateral oophorectomy for OTC can be performed safely, in combination with other ancillary procedures, as an outpatient procedure without delaying medical therapy for children facing a fertility-threatening diagnosis or treatment. LEVEL OF EVIDENCE: IV.

Prolonged response to sorafenib in a patient with refractory metastatic osteosarcoma and a somatic PDGFRA D846V mutation.

Outcome for patients with metastatic or recurrent/refractory osteosarcoma remains poor. Responses to sorafenib, a multikinase inhibitor, have been seen in recurrent/refractory osteosarcoma, although specific biomarkers of response have not been described. We report a partial response in a 7-year-old with refractory osteosarcoma treated with sorafenib 200 mg twice daily. Toxicities included Common Terminology Criteria for Adverse Events Grade 2 skin toxicities and growth suppression. After 51 months of therapy, he suffered a recurrence. Tumor sequencing later revealed a PDGFRA D846V mutation that was not identified in the relapse specimen. This case demonstrates prolonged partial response to sorafenib and provides a potential biomarker for response.

A Children's Oncology Group and TARGET initiative exploring the genetic landscape of Wilms tumor.

We performed genome-wide sequencing and analyzed mRNA and miRNA expression, DNA copy number, and DNA methylation in 117 Wilms tumors, followed by targeted sequencing of 651 Wilms tumors. In addition to genes previously implicated in Wilms tumors (WT1, CTNNB1, AMER1, DROSHA, DGCR8, XPO5, DICER1, SIX1, SIX2, MLLT1, MYCN, and TP53), we identified mutations in genes not previously recognized as recurrently involved in Wilms tumors, the most frequent being BCOR, BCORL1, NONO, MAX, COL6A3, ASXL1, MAP3K4, and ARID1A. DNA copy number changes resulted in recurrent 1q gain, MYCN amplification, LIN28B gain, and MIRLET7A loss. Unexpected germline variants involved PALB2 and CHEK2. Integrated analyses support two major classes of genetic changes that preserve the progenitor state and/or interrupt normal development.

Significance of TP53 Mutation in Wilms Tumors with Diffuse Anaplasia: A Report from the Children's Oncology Group.

PURPOSE: To investigate the role and significance of TP53 mutation in diffusely anaplastic Wilms tumors (DAWTs). EXPERIMENTAL DESIGN: All DAWTs registered on National Wilms Tumor Study-5 (n = 118) with available samples were analyzed for TP53 mutations and copy loss. Integrative genomic analysis was performed on 39 selected DAWTs. RESULTS: Following analysis of a single random sample, 57 DAWTs (48%) demonstrated TP53 mutations, 13 (11%) copy loss without mutation, and 48 (41%) lacked both [defined as TP53-wild-type (wt)]. Patients with stage III/IV TP53-wt DAWTs (but not those with stage I/II disease) had significantly lower relapse and death rates than those with TP53 abnormalities. In-depth analysis of a subset of 39 DAWTs showed seven (18%) to be TP53-wt: These demonstrated gene expression evidence of an active p53 pathway. Retrospective pathology review of TP53-wt DAWT revealed no or very low volume of anaplasia in six of seven tumors. When samples from TP53-wt tumors known to contain anaplasia histologically were available, abnormal p53 protein accumulation was observed by immunohistochemistry. CONCLUSIONS: These data support the key role of TP53 loss in the development of anaplasia in WT, and support its significant clinical impact in patients with residual anaplastic tumor following surgery. These data also suggest that most DAWTs will show evidence of TP53 mutation when samples selected for the presence of anaplasia are analyzed. This suggests that modifications of the current criteria to also consider volume of anaplasia and documentation of TP53 aberrations may better reflect the risk of relapse and death and enable optimization of therapeutic stratification. Clin Cancer Res; 22(22); 5582-91. ©2016 AACR.

Recurrent DGCR8, DROSHA, and SIX homeodomain mutations in favorable histology Wilms tumors.

We report the most common single-nucleotide substitution/deletion mutations in favorable histology Wilms tumors (FHWTs) to occur within SIX1/2 (7% of 534 tumors) and microRNA processing genes (miRNAPGs) DGCR8 and DROSHA (15% of 534 tumors). Comprehensive analysis of 77 FHWTs indicates that tumors with SIX1/2 and/or miRNAPG mutations show a pre-induction metanephric mesenchyme gene expression pattern and are significantly associated with both perilobar nephrogenic rests and 11p15 imprinting aberrations. Significantly decreased expression of mature Let-7a and the miR-200 family (responsible for mesenchymal-to-epithelial transition) in miRNAPG mutant tumors is associated with an undifferentiated blastemal histology. The combination of SIX and miRNAPG mutations in the same tumor is associated with evidence of RAS activation and a higher rate of relapse and death.