Advances in Wilms Tumor Treatment and Biology: Progress Through International Collaboration

Clinical trials in Wilms tumor (WT) have resulted in overall survival rates of greater than 90%. This achievement is especially remarkable because improvements in disease-specific survival have occurred concurrently with a reduction of therapy for large patient subgroups. However, the outcomes for certain patient subgroups, including those with unfavorable histologic and molecular features, bilateral disease, and recurrent disease, remain well below the benchmark survival rate of 90%. Therapy for WT has been advanced in part by an increasingly complex risk-stratification system based on patient age; tumor stage, histology, and volume; response to chemotherapy; and loss of heterozygosity at chromosomes 1p and 16q. A consequence of this system has been the apportionment of patients into such small subgroups that only collaboration between large international WT study groups will support clinical trials that are sufficiently powered to answer challenging questions that move the field forward. This article gives an overview of the Children's Oncology Group and International Society of Pediatric Oncology approaches to WT and focuses on four subgroups (stage IV, initially inoperable, bilateral, and relapsed WT) for which international collaboration is pressing. In addition, biologic insights resulting from collaborative laboratory research are discussed. A coordinated expansion of international collaboration in both clinical trials and laboratory science will provide real opportunity to improve the treatment and outcomes for children with renal tumors on a global level.

Wilms' tumor and other renal tumors of childhood: a selective review from the National Wilms' Tumor Study Pathology Center

Selected studies of Wilms' tumor and related renal neoplasms in children, which have been based on the National Wilms' Tumor Study Pathology Center collection of more than 2,600 renal tumors of childhood, are reviewed. The purpose of the review is to illustrate the value of the collaborative approach to uncommon pathologic specimens and to distinguish several tumors often confused with Wilms' tumor, including renal adenocarcinoma, renal teratoma, and renal neurogenic tumors. The unfavorable prognostic significance of anaplastic cells in Wilms' tumor is emphasized. Two recently described clinicopathologic entities--clear cell sarcoma of kidney and malignant rhabdoid tumor of kidney--and morphologic variants often confused with Wilms' tumor or congenital mesoblastic nephroma of infancy are discussed. Clear cell sarcoma of kidney and malignant rhabdoid tumor of kidney are, apparently, distinctive neoplasms, not Wilms' tumor variants.

Melanocyte-marker-HMB-45 is regularly expressed in angiomyolipoma of the kidney

HMB-45 (melanocytic cell-specific monoclonal antibody) immunoreactivity was investigated in 10 cases of angiomyolipoma (AML) (1 with massive regional lymph node involvement) of the kidney and detected in all of them. No HMB-45 immunoreactivity was found in other tumors of the region which can occasionally be confused with AML, such as renal cell carcinoma, Wilms' tumor, and retroperitoneal sarcoma (leiomyosarcoma and liposarcoma). These findings indicate that HMB-45 is not a melanocyte-restricted marker and suggest that its expression might be useful in distinguishing AML from other tumors of the kidney and retroperitoneum.

End stage renal disease in patients with Wilms tumor: results from the National Wilms Tumor Study Group and the United States Renal Data System

PURPOSE

We sought to assess accurately the full spectrum of end stage renal disease (ESRD) in Wilms tumor survivors by combining the unique resources of the National Wilms Tumor Study Group (NWTSG) and the United States Renal Data System (USRDS), and to confirm preliminary reports of an increased incidence of ESRD in patients with the Wilms tumor-aniridia syndrome (WAGR).

MATERIALS AND METHODS

ESRD was ascertained in 5,910 patients enrolled in NWTSG studies during 1969 to 1994 by record linkage to USRDS and by direct followup. Cumulative ESRD incidence was estimated accounting for intercurrent mortality.

RESULTS

Of 115 cases of ESRD 10 (9%) were ascertained by the NWTSG alone, 13 (11%) by USRDS alone and 92 (80%) by both. Cumulative incidence of ESRD at 20 years from diagnosis of unilateral Wilms tumor was 74% for 17 patients with the Denys-Drash syndrome, 36% for 37 patients with WAGR, 7% for 125 male patients with hypospadias or cryptorchidism (genitourinary [GU] anomalies) and 0.6% for 5,347 patients with none of these conditions. The incidence of ESRD after diagnosis of bilateral Wilms tumor was 50% for the Denys-Drash syndrome (6 patients), 90% for WAGR (10), 25% for GU anomaly (25) and 12% for other (409). ESRD in patients with WAGR or GU anomalies tended to occur relatively late, often during or after adolescence.

CONCLUSIONS

The risk of ESRD is remarkably low for the majority of patients with Wilms tumor. However, those with WAGR or associated GU anomalies are at higher risk and should be screened indefinitely to facilitate prospective treatment of impaired renal function.

Pediatric renal masses: Wilms tumor and beyond

A variety of pediatric renal masses may be differentiated from Wilms tumor on the basis of their clinical and imaging features. Wilms tumor is distinguished by vascular invasion and displacement of structures and is bilateral in approximately 10% of cases. Nephroblastomatosis occurs most often in neonates and is characterized by multiple bilateral subcapsular masses, often associated with Wilms tumors. Renal cell carcinoma is unusual in children except in association with von Hippel-Lindau syndrome and typically occurs in the 2nd decade. Mesoblastic nephroma is the primary consideration in a neonate with a solid renal mass. Multilocular cystic renal tumor is suggested by a large mass with multiple cysts and little solid tissue. Clear cell sarcoma is distinguished by frequent skeletal metastases, and rhabdoid tumor is distinguished by its association with brain neoplasms. Angiomyolipoma frequently contains fat and is associated with tuberous sclerosis. Renal medullary carcinoma occurs in patients with sickle cell trait or hemoglobin SC disease and manifests as an infiltrative mass with metastases. Ossifying renal tumor of infancy is differentiated from mesoblastic nephroma by the presence of ossified elements. Metanephric adenoma lacks specific features but is always well defined. Renal lymphoma is characterized by multiple homogeneous masses, often with associated adenopathy.

Multilocular cyst of the kidney (cystic nephroma) and cystic, partially differentiated nephroblastoma. Terminology and criteria for diagnosis

The entities commonly known as multi-locular cyst of the kidney (MLC) and cystic partially differentiated nephroblastoma (CPDN) were reviewed, based on material in the National Wilms' Tumor Study Pathology Center. The authors recommend several modifications of existing terminology and definitional criteria for these lesions. Because MLC probably represents a neoplastic lesion, the designation "cystic nephroma" (CN) is preferred. This term should be used only for predominantly cystic tumors composed entirely of differentiated tissues, without blastema or other embryonal elements. The designation CPDN should be applied to predominantly cystic lesions, lacking nodular solid regions, in which blastemal or other embryonal cells are present in the septa of the cysts. Solid Wilms' tumor with multifocal cystic change should be distinguished from CPDN. Five cases of CN and 18 cases of CPDN were reviewed. No CN, for which follow-up data was available, showed aggressive behavior. Only one case of CPDN underwent local recurrence, and there were no metastases. In general, nephrectomy alone appears to be adequate therapy for CPDN, but regular monitoring by noninvasive techniques would seem advisable.

Management of Wilms' tumour: current practice and future goals

Most patients with Wilms' tumour in Europe and North America can be cured with treatment and subsequently lead a normal adulthood. However, for some, therapy as applied today results in long-term side-effects and creates a substantial burden on quality of life. Therefore, investigators involved in the management of patients with Wilms' tumour are increasingly focusing their efforts on curtailing the long-term sequelae of therapy. This aim has been achieved by lowering the total amount of chemotherapy, radiotherapy, or both administered to patients who have characteristics associated with favourable outcome. Although excellent survival has been maintained, many patients receive less therapy today than patients with similar characteristics did a decade or two ago. Better understanding of the biological processes that lead to this childhood cancer will allow further improvements in its management.

The UMBRELLA SIOP-RTSG 2016 Wilms tumour pathology and molecular biology protocol

On the basis of the results of previous national and international trials and studies, the Renal Tumour Study Group of the International Society of Paediatric Oncology (SIOP-RTSG) has developed a new study protocol for paediatric renal tumours: the UMBRELLA SIOP-RTSG 2016 protocol (the UMBRELLA protocol). Currently, the overall outcomes of patients with Wilms tumour are excellent, but subgroups with poor prognosis and increased relapse rates still exist. The identification of these subgroups is of utmost importance to improve treatment stratification, which might lead to reduction of the direct and late effects of chemotherapy. The UMBRELLA protocol aims to validate new prognostic factors, such as blastemal tumour volume and molecular markers, to further improve outcome. To achieve this aim, large, international, high-quality databases are needed, which dictate optimization and international harmonization of specimen handling and comprehensive sampling of biological material, refine definitions and improve logistics for expert review. To promote broad implementation of the UMBRELLA protocol, the updated SIOP-RTSG pathology and molecular biology protocol for Wilms tumours has been outlined, which is a consensus from the SIOP-RTSG pathology panel.

Benign mixed epithelial and stromal tumor of the kidney

We describe a distinctive benign tumor of the kidney in a 48-year-old woman, which was composed of well differentiated ducts set in the spindle cell stroma which was muscle actin, smooth muscle actin and desmin positive, and was morphologically similar to the ovarian stroma. No immature appearing epithelial renal or mesenchymal tissue was present in the tumor. Histologically, the tumor differed from the nephrogenic adenofibroma and the rare cases of adult Wilms tumors, mesoblastic nephromas and cystic nephromas.

The role of biopsy in the diagnosis of renal tumors of childhood: Results of the UKCCSG Wilms tumor study 3

BACKGROUND

The United Kingdom Children's Cancer Study Group (UKCCSG) Wilms Tumor Study 3 has adopted preoperative chemotherapy for Wilms tumors (WT), but required prechemotherapy biopsy for histologic diagnosis. The aims of this review were to assess the usefulness and safety of prechemotherapy biopsy and to compare histologic features of WT before and after chemotherapy.

PROCEDURE

There were 286 eligible patients but only 241 biopsies and 226 nephrectomy case slides were submitted for panel review. The presence of different histologic components of WT before and after chemo therapy was retrospectively assessed.

RESULTS

Among the 241 cases, the biopsy material in 9 (4%) was not diagnostic, in 28 (12%) that were clinically and radiologically consistent with WT, the biopsy revealed tumors other than WT, and in the remaining 204 (85%) WT was confirmed. Of 188 WT suitable cases, blastema was found in 89% of tumors at biopsy, but in only 50% at nephrectomy; the remainder were either completely necrotic (17%) or showed only epithelial and/or stromal elements (33%). Of 182 children who had percutaneous cutting needle biopsy (PCNB), a fall in haemoglobin (20% of cases) and local pain (19%) were the most common complications. One child required emergency nephrectomy due to massive intratumoral bleeding, another had tumor rupture and subsequently died, and a third developed a needle track recurrence 8 months after the biopsy.

CONCLUSIONS

A number of renal tumors (12%) can have the correct histologic diagnosis made by PCNB. Preoperative chemo therapy markedly decrease in the number of samples with preserved blastema. The morbidity associated with PCNB is small. Needle biopsy of any renal mass prior to initiation of chemotherapy is recommended.

Immunohistochemical expression of WT1 by desmoplastic small round cell tumor: a comparative study with other small round cell tumors

Desmoplastic small round cell tumors (DSRCTs) present a reciprocal chromosomal translocation, t(11;22)(p13;q12), that results in fusion of Ewing's sarcoma and Wilms' tumor (WT1) genes. The authors evaluated 15 DSRCTs and 71 other tumors often considered in the differential diagnosis for immunoreactivity using a polyclonal antibody directed against the WT1 part of the chimeric protein resulting from this translocation. WT1 immunostaining was performed on paraffin material using the WT(C-19) antibody after heat-antigen retrieval. All the DSRCTs (15 of 15, 100%) demonstrated strong WT1 nuclear immunoreactivity. Ten of 14 nephroblastomas (71%) disclosed WT1-positive nuclei in accordance with the staining reported by others, and rare and focal nuclear positivity was detected in two of 17 rhabdomyosarcomas. WT1 immunoreactivity was not observed in Ewing's sarcoma/primitive neuroectodermal tumors (zero of 21, 0%), neuroblastomas (zero of 17, 0%), or rhabdoid tumors of the kidney (zero of two, 0%). In nephroblastoma, differential diagnosis with DSRCT was not difficult: Clinical and morphologic data are not similar for these two entities. The current study validates WT1 immunoreactivity as a useful marker to separate DSRCT from other small round cell tumors.

Tumour surveillance in Beckwith-Wiedemann syndrome and hemihyperplasia: a critical review of the evidence and suggested guidelines for local practice

There is strong evidence for an association between overgrowth disorders such as Beckwith-Wiedemann syndrome and the development of neoplasia. An increased cancer risk has also been observed in individuals with isolated hemihyperplasia. We critically review the evidence for tumour surveillance in Beckwith-Wiedemann syndrome and isolated hemihyperplasia and suggest local practice guidelines.

Wilms tumour

Wilms tumour (WT) is a childhood embryonal tumour that is paradigmatic of the intersection between disrupted organogenesis and tumorigenesis. Many WT genes play a critical (non-redundant) role in early nephrogenesis. Improving patient outcomes requires advances in understanding and targeting of the multiple genes and cellular control pathways now identified as active in WT development. Decades of clinical and basic research have helped to gradually optimize clinical care. Curative therapy is achievable in 90% of affected children, even those with disseminated disease, yet survival disparities within and between countries exist and deserve commitment to change. Updated epidemiological studies have also provided novel insights into global incidence variations. Introduction of biology-driven approaches to risk stratification and new drug development has been slower in WT than in other childhood tumours. Current prognostic classification for children with WT is grounded in clinical and pathological findings and in dedicated protocols on molecular alterations. Treatment includes conventional cytotoxic chemotherapy and surgery, and radiation therapy in some cases. Advanced imaging to capture tumour composition, optimizing irradiation techniques to reduce target volumes, and evaluation of newer surgical procedures are key areas for future research.

Screening of children with hemihypertrophy, aniridia, and Beckwith-Wiedemann syndrome in patients with Wilms tumor: a report from the National Wilms Tumor Study

To evaluate the usefulness of regular radiographic screening to detect an asymptomatic intraabdominal tumor in patients with an increased risk of developing Wilms tumor, we reviewed the files of patients with hemihypertrophy, aniridia, or Beckwith-Wiedemann syndrome who were registered on the National Wilms Tumor Studies. Screening was employed infrequently in the management of children with hemihypertrophy, with only 25% (6/24) of those whose hemihypertrophy was identified more than 30 days prior to the diagnosis of Wilms tumor undergoing such examinations. Most patients with aniridia were evaluated regularly for the occurrence of Wilms tumor. There were more stage 1 tumors identified in patients whose tumor was detected only through radiographic evaluation. The role of routine radiographic screening needs to be carefully evaluated in a homogeneous group of patients such as those with aniridia using a prospective study design to determine if such screening improves the survival rate of children with this rapidly growing, but readily treatable form of childhood cancer.

Age distributions, birth weights, nephrogenic rests, and heterogeneity in the pathogenesis of Wilms tumor

BACKGROUND

The National Wilms Tumor Study (NWTS) constitutes a unique resource for study of clinical, pathologic, and epidemiologic features of Wilms tumor (WT).

PROCEDURE

Data from NWTS-3,4,5 were compiled for 7,455 patients with tumors of favorable (FH) or anaplastic (AH) histology. The associations of birth weight (BW) and age-at-onset with gender, intralobar (ILNR), and perilobar (PLNR) nephrogenic rests, tumor focality, congenital malformation syndromes, and tumor histology were analyzed using descriptive statistics and linear regression.

RESULTS

Mean BWs for male and female patients without PLNR were 3.52 and 3.36 kg, respectively, and for those with PLNR were 0.12 kg and 0.15 kg heavier. Mean age was 45 months for males with no rests whose tumors were unifocal and of triphasic favorable histology. ILNR or multifocality decreased the mean age by 18 and 10 months, respectively, whereas female gender, blastemal/FH or AH increased it by 3, 10, and 16 months. Over 90% of multifocal tumors occurred in the presence of demonstrated ILNR or PLNR or both. The apparent bimodality of the age distributions and later mean ages-at-onset for females with both unifocal and multifocal tumors were explained in part by the relative deficit in females of ILNR versus PLNR-associated tumors.

CONCLUSIONS

These observations support the view that there are multiple pathways to Wilms tumorigenesis. They will facilitate selection of informative subgroups of patients for molecular analysis that may serve to identify the putative pathway for the majority of patients who cannot be classified provisionally on the basis of ILNR or PLNR.

Rhabdoid tumour of the kidney: a clinicopathological study of 22 patients from the International Society of Paediatric Oncology (SIOP) nephroblastoma file

We present 22 (0.9%) cases of rhabdoid tumour of the kidney diagnosed amongst 2392 renal tumours in children. The patients ages ranged from 3 weeks to 94 months (median 7 months) and the female:male ration was 1.2:1. Clinically, they presented with an abdominal mass but four (18%) children also had hypercalcaemia and one (4.5%) developed a brain tumour (primitive neuroectodermal tumour). None of the children presented with stage I disease, five (23%) had stage II, ten (46%) stage III, and five (23%) stage IV disease. Two (9%) patients had bilateral tumours. Histologically, the vast majority (20/22) of the tumours exhibited a classical pattern but other histological patterns were also noted. Immunohistochemical studies performed in 12 cases showed vimentin positivity in all cases, CAM 5.2 in eight, epithelial membrane antigen in six, neuron specific enolase in four, S-100 protein in eight, and desmin in one case. In only 12 of the 22 tumours was there agreement between the reporting pathologist and the panel on a diagnosis of rhabdoid tumour of the kidney. Eight tumours originally diagnosed as rhabdoid tumour of the kidney were found to be other renal tumours and in another ten cases the initial diagnosis was changed by the panel to rhabdoid tumour. Metastases developed in 18 (82%) of the children--in eight they were present at the time of diagnosis and in 10 they developed from 2 weeks to 9 months after initial diagnosis. Metastases were found in the lung, abdomen, lymph nodes, liver, bone and brain. Of the 19 children with adequate follow-up, only two (10.5%) with stage II disease are alive, while 17 (89.5%) died 2 weeks to 20 months after the diagnosis.

Wilms' tumor. Overview of National Wilms' Tumor Study Group results

Since its inception in 1969, the NWTSG has performed successful studies that are now the model for the management of pediatric malignancies. Future studies may use genetic markers to stratify high-risk patients beyond the traditional staging system. Therapy will continue to be evaluated to determine the minimal therapy necessary to achieve the best outcome for children with Wilms' tumor.

Multilocular cystic renal tumor in children: radiologic-pathologic correlation

Multilocular cystic renal tumor is a term that encompasses two histologically distinct but grossly indistinguishable lesions: cystic nephroma and cystic partially differentiated nephroblastoma (CPDN). Cystic nephroma is a segmental, purely cystic mass characterized by multiple septations composed entirely of differentiated tissues, without blastemal elements. CPDN is also a multiloculated lesion without nodular solid components, but its septa contain embryonal cells. Multilocular cystic tumors primarily affect boys during early childhood, with a substantial number of the lesions containing blastema (CPDN), and adult women, with lesions that more commonly lack septal blastema (cystic) nephroma). As a rule, nephrectomy is curative and the clinical course benign, but CPDN may recur locally. Although cystic nephroma and CPDN cannot be distinguished radiologically, failure to do so has no practical impact on management, since all of these tumors are surgically removed. However, the differential diagnosis includes other pediatric cystic renal masses that may require different treatment stratagems: Wilms tumor with cyst formation due to hemorrhage and necrosis, cystic clear cell sarcoma, cystic mesoblastic nephroma, cystic renal cell carcinoma, multicystic dysplastic kidney, and segmental multicystic dysplasia in a duplicated renal collecting system.

Identification of new Wilms tumour predisposition genes: an exome sequencing study

BACKGROUND

Wilms tumour is the most common childhood renal cancer and is genetically heterogeneous. While several Wilms tumour predisposition genes have been identified, there is strong evidence that further predisposition genes are likely to exist. Our study aim was to identify new predisposition genes for Wilms tumour.

METHODS

In this exome sequencing study, we analysed lymphocyte DNA from 890 individuals with Wilms tumour, including 91 affected individuals from 49 familial Wilms tumour pedigrees. We used the protein-truncating variant prioritisation method to prioritise potential disease-associated genes for further assessment. We evaluated new predisposition genes in exome sequencing data that we generated in 334 individuals with 27 other childhood cancers and in exome data from The Cancer Genome Atlas obtained from 7632 individuals with 28 adult cancers.

FINDINGS

We identified constitutional cancer-predisposing mutations in 33 individuals with childhood cancer. The three identified genes with the strongest signal in the protein-truncating variant prioritisation analyses were TRIM28, FBXW7, and NYNRIN. 21 of 33 individuals had a mutation in TRIM28; there was a strong parent-of-origin effect, with all ten inherited mutations being maternally transmitted (p=0·00098). We also found a strong association with the rare epithelial subtype of Wilms tumour, with 14 of 16 tumours being epithelial or epithelial predominant. There were no TRIM28 mutations in individuals with other childhood or adult cancers. We identified truncating FBXW7 mutations in four individuals with Wilms tumour and a de-novo non-synonymous FBXW7 mutation in a child with a rhabdoid tumour. Biallelic truncating mutations in NYNRIN were identified in three individuals with Wilms tumour, which is highly unlikely to have occurred by chance (p<0·0001). Finally, we identified two de-novo KDM3B mutations, supporting the role of KDM3B as a childhood cancer predisposition gene.

INTERPRETATION

The four new Wilms tumour predisposition genes identified-TRIM28, FBXW7, NYNRIN, and KDM3B-are involved in diverse biological processes and, together with the other 17 known Wilms tumour predisposition genes, account for about 10% of Wilms tumour cases. The overlap between these 21 constitutionally mutated predisposition genes and 20 genes somatically mutated in Wilms tumour is limited, consisting of only four genes. We recommend that all individuals with Wilms tumour should be offered genetic testing and particularly, those with epithelial Wilms tumour should be offered TRIM28 genetic testing. Only a third of the familial Wilms tumour clusters we analysed were attributable to known genes, indicating that further Wilms tumour predisposition factors await discovery.

FUNDING

Wellcome Trust.

Localized cystic disease of the kidney

OBJECTIVE

Localized cystic disease of the kidney is a benign nonsurgical condition. Its imaging and clinical features are characterized and differentiated from autosomal dominant polycystic kidney disease, multilocular cystic nephroma, and cystic neoplasm.

MATERIALS AND METHODS

Localized cystic disease was diagnosed in 18 patients on the basis of a review of imaging studies, clinical histories, and pathologic proof in four of the 18 patients. Average age at diagnosis was 54 years (age range, 24-83 years). Fifteen of the patients (83%) were men. CT was performed on 18 patients, sonography on nine, excretory urography on six, arteriography on four, and MR imaging on two.

RESULTS

Localized cystic disease was unilateral in all patients and characterized by multiple cysts of various sizes separated by normal (or atrophic) renal tissue in a conglomerate mass suggestive of cystic neoplasm. In some patients, involvement of the entire kidney, which was suggestive of unilateral autosomal dominant polycystic kidney disease, was seen. No cysts were seen in the contralateral kidney in 14 patients, and only one or two scattered small cysts were present in four patients. Clinical presentations included hematuria, flank pain, palpable abdominal mass, and localized cystic disease as an incidental finding. None of the patients had a family history of autosomal dominant polycystic kidney disease. Ten patients underwent follow-up (follow-up range, 1-12 years); nine patients underwent imaging follow-up and one patient underwent clinical follow-up, which showed stability of disease. Four patients underwent nephrectomy for suspected renal neoplasm.

CONCLUSION

Familiarity with localized cystic disease of the kidney and its imaging findings is important to avoid unnecessary surgery and to differentiate the disease from autosomal dominant polycystic kidney disease.

Characteristics and outcome of children with Beckwith-Wiedemann syndrome and Wilms' tumor: a report from the National Wilms Tumor Study Group

PURPOSE

Children with Beckwith-Wiedemann syndrome (BWS) are at increased risk for developing Wilms' tumor (WT). We reviewed the National Wilms Tumor Study Group (NWTSG) records to assess clinical characteristics and outcome of patients with WT and BWS.

METHODS

In the NWTSG, treating clinicians were asked to report, for each enrolled patient, whether the patient had BWS. Between 1980 and 1995, 4,669 patients were treated on two consecutive NWTSG protocols (NWTS 3 and NWTS 4). We retrospectively reviewed the clinical characteristics and treatment outcomes of BWS patients compared with patients with WT without BWS.

RESULTS

Fifty-three children enrolled onto NWTS 3 and 4 were reported to have BWS. BWS patients were more likely to present with lower-stage tumors (P =.0001), with more than half (27 of 53) presenting with stage I disease. The overall treatment outcomes for the BWS patients were nearly identical to those without BWS, with overall survival at 4 years from diagnosis at 89% and 90%, respectively. Overall, 21% of the patients with BWS had bilateral disease, either at diagnosis (nine of 53) or as metachronous contralateral recurrence (two of 53). BWS patients enrolled onto NWTS 4 had smaller tumors than those enrolled onto NWTS 3 (P =.02), a trend not seen in the non-BWS patients.

CONCLUSION

Like children without BWS, children with BWS and WT have an excellent prognosis with modern treatment regimens. There is a high risk of bilateral disease, and increasingly smaller tumors are being detected. This suggests that a national trial assessing the role of ultrasound screening followed by nephron-sparing surgery for some patients may be appropriate.

Natural history and treatment of Wilms's tumour: an analysis of 335 cases occurring in England and Wales 1962-6

Hospital records and other data relating to Wilms's tumour were analysed to elucidate both thenatural history of the disease and the effects of treatment, with special reference to actinomycin D. The age of maximum incidence was about 18 months; left-sided tumours were significantly more common than right-sided ones.Prognosis was related to stage of the disease at the initial operation and to the occurrence of metastasis. The three-year survival rate for cases having a nephrectomy was 35%; no child who did not have a nephrectomy survived.Recurrence of the tumour was observed in two-thirds of the cases, almost always within two years of the initial treatment, irrespective of the child's age. The three-year survival rate for this group was 11%.The effects of radiotherapy and chemotherapy are considered in detail. Very little improvement in survival rate could be ascribed to actinomycin D. The reasons for this and for the variations found in earlier reports on selected cases are possibly the addition of other components of treatment and differences in drug regimens. The findings suggest the need for controlled clinical trials.

The occurrence of Wilms tumor in horseshoe kidneys: a report from the National Wilms Tumor Study Group (NWTSG)

BACKGROUND/PURPOSE

An increased incidence of Wilms tumor has been noted in patients with a horseshoe kidney. These represent a difficult diagnostic and therapeutic challenge. The charts of all National Wilms Tumor Study Group (NWTSG) patients with Wilms tumor occurring in a horseshoe kidney were reviewed.

METHODS

From 1969 to 1998, 8,617 patients were enrolled in the NWTSG. Forty-one patients were found to have a Wilms tumor arising in a horseshoe kidney for an incidence of 0.48%. Their records were reviewed retrospectively.

RESULTS

Horseshoe kidney was not recognized preoperatively in 13 patients, 10 of whom were evaluated with computed tomography (CT). Four of the 10 also had renal ultrasonography and one an intravenous pyelogram (IVP). Two of the 13 were evaluated with an IVP only, and the last had no preoperative imaging studies performed. Stage at presentation was stage I, 10 pts; stage II, 10; stage III, 12; stage IV, 6; stage V, 3. Primary surgical resection was performed in 26 patients, including 23 nephrectomies and 3 partial nephrectomies. Fifteen children were treated with preoperative chemotherapy after initial biopsy of the tumor. The mean total remaining renal parenchyma after all operations (excluding treatment of relapses) was approximately 75%. Surgical complications occurred in 14.6% of patients, including 2 urine leaks, 2 ureteral obstructions, and 1 ureteral injury. Two patients had transient renal failure.

CONCLUSIONS

The diagnosis of horseshoe kidney often was missed on preoperative imaging. Accurate preoperative diagnosis is important in planning the operative approach and may help to decrease complications related to transection of the urinary collecting system. Although 37% of patients with Wilms tumor arising in a horseshoe kidney were judged inoperable at initial exploration, all were amenable to resection after chemotherapy.