Failure pattern and factors predictive of local failure in Rhabdomyosarcoma: A report of group III patients on the third intergroup Rhabdomyosarcoma Study

Purpose: To analyze patterns of failure and factors predictive of local treatment failure in children enrolled on the third Intergroup Rhabdomyosarcoma Study who had either biopsy only or subtotal resection of their primary tumor, had no distant metastases, and received radiation therapy for local control. Patients and Methods: Treatment failure was categorized as local, regional nodal, or distant metastatic. The 5-year cumulative risk of failure was estimated for each category and factors predictive of local failure risk were determined using the Cox model and binary recursive partitioning. Results: The estimated 5-year cumulative incidence rates by failure category were: total local (with or without concurrent regional or distant failure), 19%; total regional nodal, 2%; total distant, 11%; and death from toxicity or unknown recurrence type, 4%. Lymph node involvement at diagnosis was the single factor most predictive of increased total local failure risk (5-year cumulative incidence 32%) compared with children with negative nodes or unknown node status (16%). No significant effect on local failure risk was observed by total radiotherapy dose over the prescribed range of 41.4 Gy to 50.4 Gy. For all patients (N = 405), the estimated 5-year failure-free survival and overall survival were, respectively, 70% and 78%. Conclusion: Local failure after radiotherapy for group III rhabdomyosarcoma patients is the predominant type of relapse. Involved lymph nodes at diagnosis predict a higher risk of local and distant treatment failure compared with patients whose lymph nodes are negative.