Wilm's Tumor

Hello everyone - Here is a senario I cannot work out for sure, but I "think" I know the answer.

A child presents with a large unilateral renal mass, ? Wilm's Tumor.  It appears too large to remove without neo-adjuvant chemotherapy.  A biopsy is done which confirms Wilm's Tumor and the child receives 4 doses of neo-adjuvant chemotherapy.  A nephrectomy is performed and the 1.5kg tumor removed without introperative splliage. There is no lymphovascular invasion, the margins are clear, and histology is favourable.

From the NCI's website (link below), this child has Stage III Wilm's Tumor and should be treated accordingly - nephrectomy, post-operative chemo and radiation.  This is soley based on the fact that the child had the tumor biopsied pre-operatively, as they do not meet any other criteria for Stage II or III.  Is this correct?  Is there ANY way that this child could be staged as Stage I and not receive any post-operative chemo?

http://www.cancer.gov/cancertopics/pdq/treatment/wilms/HealthProfessional/page3

Many thanks.