[1] Childrens Canc Inst, Porto Alegre, RS, Brazil
[2] Hosp Pereira Rossell, Montevideo, Uruguay
[3] Univ Fed Sao Paulo, Dept Pediat, Pediat Oncol Inst IOP GRAACC UNIFESP, Sao Paulo, SP, Brazil
[4] Fundacao Pio XII Hosp Infantojuvenil, Barretos, SP, Brazil
[5] Hosp Canc AC Camargo, Sao Paulo, SP, Brazil
[6] Hosp Clin Sao Paulo ITACI, Sao Paulo, SP, Brazil
[7] Hosp Crianca Santo Antonio, Porto Alegre, RS, Brazil
[8] Dana Farber Canc Inst, Boston, MA 02115 USA
[9] Hosp Univ Santa Maria, Santa Maria, RS, Brazil
[10] Hosp Infantil Pequeno Principe, Curitiba, PR, Brazil
[11] Santa Casa Misercordia Sao Paulo, Sao Paulo, SP, Brazil
[12] Inst Clin Pediat Bolivar Risso, Jundia, SP, Brazil
[13] Hosp Univ Oswaldo Cruz, Recife, PE, Brazil
[14] Hosp Napoleao Laureano, Joao Pessoa, Paraiba, Brazil
[15] Univ Fed Rio de Janeiro, Inst Pediat, Rio de Janeiro, RJ, Brazil
[16] Hosp Sao Lucas PUC RS, Porto Alegre, RS, Brazil
[17] Univ Fed Rio Grande do Sul, Dept Pediat, Hosp Clin Porto Alegre, Porto Alegre, RS, Brazil