Analysis of Stage I EFHWTs Treatment Finds Event-Free Survival and Overall Survival Rates Greater Than 95%

Data for stage I epithelial-predominant favorable-histology Wilms tumors (EFHWTs) reported greater than a 95% event-free survival rate and overall survival rate, supporting the utility of investigating the treatment of stage I EFHWTs with observation alone after nephrectomy, according to a recent study published in Cancer.

Specifically, the 4-year event-free survival (EFS) rate was 96.2% (95% CI, 92%-100%), while the 4-year overall survival (OS) rate was 100%. More, the EFS and OS rates did not statistically significantly differ with the age at diagnosis (<48 vs ≥48 months; P= .37) or treatment (EE4A vs observation only; P= .55).

“The current study examines the outcomes of all patients with stage I EFHWTs registered in a cooperative group clinical study to evaluate the feasibility of treating these patients without adjuvant chemotherapy through a retrospective review,” wrote the researchers. “To summarize, 4-year overall survival was excellent at 100% with 4-year event-free survival of 96.2%.”

A total of 6 events were reported in 6 patients, in which none of the primary tumors showed a loss of “heterozygosity of chromosomes 1p and 16q.” Of these 6, 3 patients developed contralateral tumors months after their initial diagnosis. Two of these 3 patients underwent adjuvant chemotherapy for their initial tumors, with all 3 not experiencing any relapses, and ere alive at the time this study was written.

The study examined a total of 177 patients who underwent stage I EFHWTs who underwent nephrectomy. The group was composed of 92 males and 85 females with a media age of 17.1 months, but most patients (123 of 177 [69.5%]) were younger than 48 months at the time of diagnosis. Median follow-up for patients was 3.6 years.

Of that population, 117 of the patients were treated with vincristine and dactinomycin (EE4A), while 57 patients were treated with observation only because of their very low-risk Wilms tumors designation.

“These findings provide a further rationale for the investigation of conservative management of these patients with observation only after surgery in a clinical trial setting,” wrote the researchers. “Within this setting, it will also be possible to establish the interobserver correlation between institutional and central pathology review when tumors are being reclassified as epithelial predominant.”

This study was limited by the lack of randomization when assigning patients to chemotherapy treatment or observational treatment groups. More, the researchers do not have the molecular characterization of the TRIM28 or BRAFV600E mutations, limiting their understanding of recurrences.

Given the limited number of patients who developed recurrent disease, the researchers simply reported the characteristics of these patients. Finally, the researchers relied on “institutional recognition and reporting of predisposition syndromes,” therefore this cannot be completely excluded from the explanation of contralateral recurrences.

“Because of the somewhat arbitrary definitions of very low-risk Wilms tumors, this success suggests that there may be opportunities to expand the current definitions to allow more patients to be spared the toxicities associated with chemotherapy,” wrote the researchers. “The subject of the current study is stage I FHWTs of all ages showing an epithelial-predominant histology.”

Reference:

Parsons LN, Mullen EA, Geller JI, et al. Outcome Analysis of Stage I Epithelial-Predominant Favorable-Histology Wilms Tumors: A Report From Children's Oncology Group Study AREN03B2. Cancer. DOI: 10.1002/cncr.32855.