Rhabdomyosarcoma in infants younger than 1 year: a report from the Children's Oncology Group.

Background: Rhabdomyosarcoma (RMS), the most common soft-tissue sarcoma in children, occurs less commonly in infants. Historically, poorer outcomes have been reported for infants diagnosed with RMS than for older children.

Methods: The authors analyzed the characteristics, treatment administered, outcomes, and patterns of failure for infants aged < 1 year with nonmetastatic RMS who received multimodal therapy on Intergroup Rhabdomyosarcoma Study (IRS) protocols IRS-IV, D9602, and D9803.

Results: Seventy-six infants with nonmetastatic RMS were treated on the 3 protocols from 1991 to 2005. Their median age was 7.4 months (range, 0.1-12 months). Tumor histology included embryonal (57%), alveolar (21%), and undifferentiated sarcoma/other (22%). A parameningeal primary tumor site was less common in this infant cohort (3%) than in all patients who were treated on IRS-IV (25%). The estimated 5-year failure-free survival and overall survival rates (95% confidence interval [CI]) were 57% (95% CI, 44%-67%) and 76% (95% CI, 65%-85%), respectively, for infants compared with 81% (95% CI, 79%-83%) and 87% (95% CI, 85%-89%), respectively, for children ages 1 to 9 years. Twenty-three of 32 infants with treatment failure had local recurrence/progression with distant failure (n = 3) or without distant failure (n = 20). The overall local failure rate was 30%. The median time to treatment failure was 13 months. The failure-free survival rate was worse for infants who had IRS Group III tumors and for those who received less than protocol-recommended radiation therapy.

Conclusions: Infants with RMS appeared to have worse outcomes than older patients, in part because of high rates of local failure. The authors concluded that concerns regarding morbidity in infants and reluctance to use aggressive local control measures may lead to higher rates of local failure.