B7-H1 as a Biomarker for Therapy Failure in Patients with Favorable Histology Wilms Tumor

Purpose: A minority of children with Wilms tumor will experience tumor recurrence. In a previous pilot study we found an association between expression of an immune costimulatory molecule, B7-H1, and tumor recurrence in favorable histology Wilms tumor. We sought to verify the prognostic value of B7-H1 as a biomarker in favorable histology Wilms tumor. Materials and Methods: We performed a nested case-control study of tumors from the Fifth National Wilms Tumor Study. We randomly selected 44 children unsuccessfully treated (cases) and 49 who were successfully treated for favorable histology Wilms tumor (controls). Cases and controls were matched based on tumor stage, and the analysis was restricted to children who underwent initial resection. We excluded patients with stage IV or V disease and those treated with chemotherapy or radiation. Tumor specimens were stained for B7-H1 expression. Results: Of the 93 total samples analyzed 60 (65%) demonstrated B7-H1 staining, with staining diffusely present in 13 (22%) and blastema predominant in 34 (57%). B7-H1 expression was associated with failure of initial therapy (p = 0.006). Patients with tumors showing less than 20% B7-H1 positive cells were at lower risk for treatment failure, while those with tumors exhibiting greater than 60% B7-H1 positive cells were at greater risk for treatment failure. This association appeared to be independent of tumor stage. Conclusions: B7-H1 expression by favorable histology Wilms tumor is associated with an increased risk of failure of initial therapy.