The NCCN document also laid out diagnostic procedures for general practice pediatricians, who are often the first to identify Wilms tumor, which largely presents in children between the ages of 1 and 5 years and most commonly with abdominal distension and/or masses, with or without other symptoms. Physicians are cautioned to palpate children’s abdomens gently to avoid tumor rupture, “which then leads to them potentially requiring more intensive therapy, specifically radiation, which has long-term side effects,” noted Douglas Harrison, MD, associate professor of pediatrics, center medical director, and inpatient medical director of The University of Texas MD Anderson Children’s Cancer Hospital who was not involved in crafting the guidelines.

A key message in the guidelines is the distinct management of patients with Wilms tumor based on whether they have a solitary cancer confined to 1 kidney or, less commonly, disease in both kidneys. Patients with unilateral tumors, if resectable, undergo nephrectomy followed by either observation or 1 of several chemotherapy regimens, depending on their initial risk group. A different approach is described in children with bilateral disease, initially unresectable tumors, or with genetic predispositions, who are likely to eventually develop another cancer in their second kidney. “We initially treat with chemotherapy to try to shrink [the tumors] down and make them more surgically resectable,” in order to preserve kidney tissue, Dr Balis said.

This preoperative chemotherapy approach achieved 4-year event-free survival and overall survival of 82.1% and 94.9%, respectively, in the COG’s AREN0534 study ( Identifier: NCT00945009) in 189 patients with bilateral tumors, representing an improvement in historical outcomes for this group.5

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Children younger than 10 years with bilateral renal lesions almost always have a diagnosis of Wilms tumor, so the need to ascertain that through diagnostic biopsy is much lower, Dr Mullen noted. The NCCN guidelines are largely in line with a general North American tendency to perform nephrectomies upfront, except in circumstances like these. “Although we recommend strongly that every patient who can get an upfront resection of their tumor [for] unilateral tumors, there’s increasing recognition that sometimes that’s not safe or appropriate for the child — the tumor is too big, they are too clinically ill — there are different [reasons].”

The NCCN guidelines also include detailed information on risk-stratifying patients based on their tumors’ histopathologic and surgical stage, the presence of unfavorable tumor biomarkers, patient and tumor characteristics, and the response of pulmonary metastases to initial therapy.

Determining some of these factors accurately can be challenging with a tumor that is observed so rarely, Dr Mullen said. For instance, it is difficult to discern Wilms tumors with favorable histology from other types of pediatric renal tumors. Some of these challenges were recognized decades ago by the National Wilms Tumor Study Group, which found a 10% to 20%6 discordance between risk assessments made by local physicians and those produced by a national expert panel, she added.