Loss of heterozygosity for chromosomes 16q in Wilms tumors predicts outcomes: A meta-analysis

Abstract

BACKGROUND

The research findings suggest that the prognosis of children with Wilms tumor (WT) is affected by various factors. Some scholars have indicated that loss of heterozygosity (LOH) on chromosome 16q is associated with a poor prognosis in patients with WT.

AIM

To further elucidate this relationship, we conducted a meta-analysis.

METHODS

This meta-analysis was registered in INPLASY (INPLASY2023100060). We systematically searched databases including Embase, PubMed, Web of Science, Cochrane, and Google Scholar up to May 31, 2020, for randomized trials reporting any intrapartum fetal surveillance approach. The meta-analysis was performed within a frequentist framework, and the quality and network inconsistency of trials were assessed. Odds ratios and 95%CIs were calculated to report the relationship between event-free survival and 16q LOH in patients with WT.

RESULTS

Eleven cohort studies were included in this meta-analysis to estimate the relationship between event-free survival and 16q LOH in patients with WT (I² = 25%, P < 0.001). As expected, 16q LOH can serve as an effective predictor of event-free survival in patients with WT (risk ratio = 1.95, 95%CI: 1.52–2.49, P < 0.001).

CONCLUSION

In pediatric patients with WT, there exists a partial correlation between 16q LOH and an unfavorable treatment prognosis. Clinical detection of 16q chromosome LOH warrants increased attention to the patient’s prognosis.

Key Words: Loss of heterozygosity, Wilms tumor, Survival time, Chromosomes 16q

Core Tip: This study explores the prognostic significance of 16q loss of heterozygosity (LOH) in the treatment of patients with Wilms tumor (WT) in recent years. Utilizing a meta-analysis, the overall predictive value of 16q LOH in patients with WT is assessed. The findings indicate that 16q LOH is associated with a poor prognosis in patients with WT. Following clinical treatment, it is crucial to pay increased attention to patients’ prognostic value while adjusting their survival expectations.

INTRODUCTION

Wilms tumor (WT) the most prevalent renal embryonic malignancy in children, presents as an abdominal mass with the potential for local and distant dissemination, with approximately 10% of cases manifesting bilaterally or multicentrically. The average onset age is 42–47 months unilaterally and 30–33 months bilaterally. Treatment primarily involves surgery, with advanced cases relying on renal dialysis or transplantation. Genetic and molecular analyses of WT patient genomes reveal consistent conclusions in recent studies. Sporadic familial cases differ in pathogenesis, and in patients with other syndromes, the possibility of sex chromosome mutation should be excluded. In over 90% of sporadic cases, WT results from a high-frequency mutation of multiple chromosomes and genes. Chromosomal variations in European and American patients with WT include loss of heterozygosity (LOH) at 16q, involving chromosomal structural changes and a decrease in allele number. This meta-analysis assesses the prognostic value of 16q LOH deletion in patients with WT.

Maw et al[1] initially reported the frequency of 16q LOH variation in 1992, confirming some cases with concurrent 1p LOH. Subsequent WT studies, National WT Study (NWTS)-3 and NWTS-4, revealed an adverse prognosis associated with 1p or 16q LOH. Similar confirmations of the association between 16q LOH and poor prognosis were reported in studies from the United Kingdom and Germany[2]. Another Italian study further confirmed the association of 1p LOH with poor prognosis[3-5]. Based on this foundation, the NWTS-5 research project by Grundy et al[6] evaluated over 1700 patients with WT, indicating an increased risk of recurrence or death with 1p or 16q LOH, especially when occurring simultaneously, affecting 5% of enrolled patients. Parallel research by Messahel et al[7] in the United Kingdom, involving 426 patients, affirmed the mutation frequency consistency with the NWTS-5 study results.

MATERIALS AND METHODS

Search strategy

Two independent reviewers conducted a comprehensive literature search across three databases, adhering strictly to the Preferred Reporting Items for Systematic Reviews and Meta-analyses 2009 Checklist Protocol. PubMed, Cochrane, Embase, Web of Science, and Google Scholar were used. Reports published before May 31, 2020, were retrieved utilizing these keywords: (16q [Mesh]) AND [(Wilms Tumor) OR [Mesh] (Tumor, Wilms) OR (Wilms Tumor) OR (Nephroblastoma) OR (Nephroblastomas) OR (Wilms’ Tumor) OR (Tumor, Wilms’) OR (Wilm Tumor) OR (Wilm’s Tumor) OR (Bilateral Wilms Tumor) OR (Tumor, Bilateral Wilms) OR (Wilms Tumor, Bilateral)]. Preselected findings were confined to English publications. Additionally, we performed manual searches to identify potentially eligible articles that may have been overlooked by computer-based searches[8]. For a detailed methodology, reference can be made to previous works[9-11].

Study selection

Two investigators scrutinized the abstracts and titles of all literature identified using the search strategy to compile relevant articles. The full texts were subsequently examined by two different reviewers. Any disagreements were resolved through discussion or, if necessary, by the judgment of a third expert until a consensus was attained.

Inclusion and exclusion criteria

The data retrieved from the search were evaluated by two reviewers according to the title, abstract, and full text. The inclusion criteria encompassed cohort design, patients with WT, comparison of 16q LOH to a control group, survival as an outcome, and reporting of odds ratio, relative risk, hazard risk, or any data sufficient to estimate these parameters. Reviews, conference abstracts, case reports, papers, letters, and data overlapping with other studies were excluded.

Statistical analyses

The meta-analysis was performed using Cochrane Review Manager software (Rev Man 5.3). Continuous outcomes were calculated using standard mean differences, and dichotomous outcomes by risk ratios (RRs), both presented with 95%CIs. We assessed heterogeneity through forest plots and I² calculation (> 50% considered extensive heterogeneity). A fixed-effects model was employed to collate results in case of minimal heterogeneity; otherwise, a random-effects model was applied. A qualitative examination of potential publication bias was conducted using funnel plots in Rev Man software when the CI distribution significantly deviated.

RESULTS

Study selection

The literature retrieval process and results, based on research characteristics and quality evaluation, are depicted in Figure 1. Initially, 179 potentially relevant studies were identified. Eventually, 11 studies that met the inclusion criteria underwent meta-analysis. Table 1 presents the characteristics of the included studies, encompassing the number of patients, ages, follow-up time, and methods employed to detect 16q LOH. Of the 11 studies, 6 were of high quality, whereas others were of moderate quality (Table 2).

Figure 1 Flow diagram of the study.

Table 1 Characteristics of included studies.

Ref.	Country	Patients	Age	Follow-up	Method to Detect LOH 16q
Spreafico et al[27], 2013	Italy	Nonanaplastic unilateral WT of stages I to IV	Median 40 months, range 1 to 172 months	Mean = 73 months, range 35 to 97 months	Microsatellite markers
Grundy et al[6], 2005	Australia, New Zealand, Switzerland, and the Netherlands	1724 patients younger than 16 years at diagnosis with specific WT	< 16 yr	4 yr	PCR
Chagtai et al[35], 2016	26 countries: 24 in Europe, 1 in Australia, 1 in South America	586 patients with WT of stages I to IV	Range 6 months to 18 years	M = 68 months	Multiplex Ligation-ependent Probe Amplification
Messahel et al[7], 2009	United Kingdom	426 patients with favorable-histology WT	Not known	4 yr	Microsatellite markers
Grundy et al[2], 1994	United States	204 patients with histology WT	< 17 yr	M = 1.3 yr (LOH group) or 1.4 yr (control group)	PCR
Grundy et al[3], 1998	United Kingdom	40 patients with sporadic WT	Not known	≥ 7 yr	PCR
Klamt et al[4], 1998	Germany	73 patients with WT	Mean = 3.48 yr	Not known	PCR
Skotnicka-Klonowicz et al[36], 2000	Poland	58 patients with WT	M = 39 months; range = 2 d to 13 yr	M = 42 months; range = 14–139 months	PCR
Zhang et al[37], 2002	China	30 patients with WT	M = 38 months; range = 2 months to 13 yr	Not known	PCR
Kullendorff et al[38], 2003	Sweden	39 patients with WT	M = 4.2 yr, range 5 months to 15 yr	Range 7 to 160 months	Not known
Fernandez et al[22], 2017	United States, Canada, New Zealand and Israel	110 patients with very low risk WT (defined as stage I favorable histology WT with nephrectomy weight < 550 g and age at diagnosis < 2 yr)	11.5 months: 0.1 to 23 months	M = 80 months: 5 to 97 months	Multiplex Ligation-ependent Probe Amplification

LOH: Loss of heterozygosity; WT: Wilms’ tumor; M: Median.

Table 2 Quality assessment of the included studies.

Ref.	Selection	Comparability	Outcome	NOS score	Quality
Spreafico et al[27], 2013	4	1	1	6	Moderate
Grundy et al[6], 2005	4	1	1	5	Moderate
Chagtai et al[35], 2016	3	2	2	6	High
Messahel et al[7], 2009	3	1	2	5	High
Grundy et al[2], 1994	3	2	2	6	High
Grundy et al[3], 1998	3	1	2	6	High
Klamt et al[4], 1998	3	2	2	5	Moderate
Skotnicka-Klonowicz et al[36], 2000	4	2	1	5	Moderate
Zhang et al[37], 2002	3	2	2	6	High
Kullendorff et al[38], 2003	3	3	1	5	Moderate
Fernandez et al[22], 2017	3	1	2	6	High

Heterogeneity test

A heterogeneity test was conducted on the 11 studies, resulting in an I² value of 25% and a Q test P value of < 0.01, indicating no heterogeneity among the selected studies. A fixed-effects model was selected for the meta-analysis of the 11 studies, with the results depicted in Figure 2.

Figure 2 Forest plot of total effective rate.

The meta-analysis, using a fixed-effects model, revealed that the survival time of the experimental group was 1.95 times higher than that of the control group, demonstrating statistical significance (P < 0.05; Figure 2).

Publication bias

A sensitivity analysis of the 11 studies revealed distinct groupings based on different efficacy judgments and varying sensitivities (Figure 3).

Figure 3 Funnel plot of total effective rate.

The 16q LOH mechanism in WT

Drawing on the study results, a schematic figure depicting the 16q LOH mechanism causing WT was developed. The theoretical foundation of this study is based on the figure content (Figure 4).

Figure 4 The 16q loss of heterozygosity mechanism in Wilms tumor. LOH: Loss of heterozygosity.

DISCUSSION

Neoplasms continue to be a significant global health concern[12-14]. WT, as the most prevalent pediatric renal tumor, exhibits prognostic variability affected by factors such as tumor stage, histological type, age, and specific biomarkers. The NWTS, involving 232 patients with WT, initially hypothesized that LOH on chromosome 16q is a poor prognostic factor in patients with WT. However, the consensus on whether 16q LOH indeed signifies a poor prognosis remained contentious. Our previous study revealed an association between 16q LOH and an elevated risk of WT recurrence, prompting the current meta-analysis to elucidate the association between 16q LOH and survival in patients with WT.

LOH is the loss of one allele on a chromosome pair, leaving the paired chromosome intact[15]. Another related state is homozygous deletion, where both alleles on a chromosome pair are lost. This mechanism has been confirmed in diseases such as retinoblastoma, where the LOH of the RB1 allele contributes to pathogenesis. Notably, in patients with congenital iris deficiency (with an incidence rate of approximately 1.4%, also known as aniridia nephroblastoma syndrome), LOH of the RBI gene on chromosome 11 is frequently observed[16].

Dix et al[15] reported a 17% rate of LOH at 16q in patients with WT. The fifth WT research report indicated a worse prognosis, especially when both 16q LOH occurrences coincided, suggesting the potential presence of genes promoting WT formation or enhancing drug resistance in these regions. Evageliou et al[17] identified the minimum region of 1p LOH in WT (between DIS2694 and DIS244 sites), revealing decreased expression of TNFRSF9 and DFFA genes, which play roles in apoptosis regulation, indicating their involvement in WT occurrence. Some scholars suggested that 16q LOH occurrence is unrelated to WT histological typing but may be associated with its occurrence. Additionally, studies have observed that patients with LOH 16q in WT had tumor metastasis in later stages[16].

The Children’s Oncology Group (COG) reported a decrease in relapse-free survival with the presence of 16q LOH (91.2% without vs 82.5% with LOH)[18,19]. Notably, Fernandez et al[20] utilized fresh specimens for analysis, whereas our data rely on formalin-fixed paraffin-embedded sample analysis, possibly explaining some discrepancies. The incidence of 16q LOH ranges from 14%–20% in various reports[21], with some studies reporting 11.9%, marginally lower than the reported incidence[22]. Despite COG trials indicating higher relapse and death risk with 16q LOH, the Society of Pediatric Oncology renal tumor consortium failed to establish a significant effect on event-free survival/overall survival. Some studies reported differences in 16q rates between relapsed patients and survivors (19% vs 4.8%), albeit not statistically significant[23,24].

While LOH is universally recognized for its adverse prognostic effects across various factors, intriguing age-related trends have been documented. Previous studies from the NWTS group and an Egyptian study have noted a lower LOH frequency in younger children[19]. Similar trends have been observed in some other studies[25]. Concurrently, older age has been associated with an increased risk of relapse in WT by multiple research groups[2]. This correlation indicates that the heightened relapse risk with older age may be attributed to specific genetic changes. If translated into clinical practice, these findings could potentially guide therapy in selected patients[26].

Chromosomal segmental deletion is a common occurrence in various genetic syndromes and tumor tissues. Chromosome LOH is frequently linked to high-grade and low differentiation of tumors. Therefore, 16q LOH is not exclusive to WT but has been reported in other tumors such as neuroblastoma and gastrointestinal tumors[27]. The International Children’s Cancer Research Institute has acknowledged 1p or 16q LOH as a crucial reference standard for WT treatment and prognosis. Efforts have been made to identify a stable and simple LOH detection method, including the examination of the expression of four microsatellite foci in these two segments[28]. D16S303, located in LOH 16q, has exhibited a correlation with tumor grade[29]. Detecting 16q LOH in WT tissue through microsatellite focal amplification holds significant implications for understanding the patient’s condition and tailoring personalized treatment approaches[30]. Treatment for WT is multimodal, with surgery being the primary method. For patients with advanced tumors undergoing nephrectomy and extrarenal tumor resection, dialysis or kidney transplantation may not be necessary. However, in specific cases of bilateral nephrectomy without nephron preservation, absence of extrarenal disease, and patients opting out of treatment, transplantation may be considered.

This study distinguishes itself from previous research, such as that of Bu et al[31], by expanding the scope of research collection and conducting a more in-depth analysis of relevant content. Tumors with loss of chromosome heterozygosity play a critical role in tumor formation[32], as a multitude of missing chromosome segments contain cell cycle regulatory and cellular metabolic regulatory genes, including 1p36, 4 Lp36, cadherin 1616q22, and SLC family proteins[33]. The loss of expression of these proteins may affect renal function, and patients with 1p or 16q LOH have reported reduced sensitivity of tumor tissue to radiotherapy and chemotherapy[34]. Understanding gene polymorphism and chromosome LOH characteristics holds significant implications for developing individualized treatment plans. Consistent with our expectations, our study confirms that 16q LOH can serve as a reliable indicator for WT (RR = 1.95, 95%CI: 1.52–2.49, P < 0.001).

Despite the valuable insights provided by this study, several limitations must be acknowledged. Firstly, the inclusion of mostly randomized controlled trial (RCT) studies is a strength, but the limited number of RCT studies specifically focusing on 16q LOH in WT restricts the generalizability of our findings. The scarcity of RCTs dedicated to individual 16q LOH hampers the robustness of the study results. Additionally, the common co-occurrence of 16q LOH with 1p LOH poses a challenge, as individual 16q LOH may not have been extensively studied in RCTs, leading to a dearth of references and potentially incomplete research outcomes. Secondly, the references included in this study primarily originate from an earlier period. The reliance on older literature may not adequately reflect the current landscape of research, especially concerning new diagnostic technologies and methods. The lack of recent references creates a gap in the understanding of the contemporary diagnostic value of 16q LOH for WT.

CONCLUSION

In conclusion, this meta-analysis highlights the poorer prognosis and significantly shorter survival time associated with 16q LOH in patients with WT compared to those without 16q LOH. The significance of this study lies in its pioneering compilation of evidence, establishing 16q LOH as a positive prognostic factor for patients with WT. However, the limitations of this study, including a small sample size of original studies and the need for larger-scale mutation center trials, underscore the necessity for further research to comprehensively elucidate the prognostic value of 16q LOH in WT.

ARTICLE HIGHLIGHTS

Research background

Wilms tumor (WT) is a prevalent childhood disease with variable treatment outcomes, primarily attributed to multi-gene mutations. Ongoing research has identified 16q loss of heterozygosity (LOH) as a site deletion linked to a poor prognosis.

Research motivation

The aim is to elucidate the relationship between 16q LOH and WT, providing effective guidance for the clinical treatment of this disease.

Research objectives

The primary objective is to determine whether 16q LOH can serve as a predictive marker for a dismal prognosis in patients with WT, utilizing statistical analysis.

Research methods

The primary objective is to determine whether 16q LOH can serve as a predictive marker for a dismal prognosis in patients with WT, utilizing statistical analysis.

Research results

Eleven cohort studies were evaluated to estimate the relationship between event-free survival and 16q LOH in patients with WT (I² = 25%, P < 0.001). As expected, 16q LOH emerged as a reliable predictor of event-free survival in patients with WT (risk ratio = 1.95, 95%CI: 1.52–2.49, P < 0.001).

Research conclusions

In pediatric patients with WT, a discernible correlation exists between 16q LOH and an unfavorable treatment prognosis. The clinical detection of chromosome 16q LOH warrants increased attention to the patient’s prognosis.

Research perspectives

Genetic mutations in the 16q LOH locus are indicative of a poor prognosis in patients with WT. However, to establish a clearer relationship between the two factors, conclusive results necessitate a larger sample size, incorporating randomized controlled trial research combined with meta-analysis.