Proton radiotherapy for infant rhabdomyosarcoma: Rethinking young age as an adverse prognostic factor

Area of Science:

• Pediatric Oncology
• Radiation Oncology
• Medical Physics

Background:

• Young age is an adverse prognostic factor in infant rhabdomyosarcoma, often leading to reduced treatment intensity.
• Proton therapy presents an opportunity to enhance the therapeutic ratio for this patient group.

Purpose of the Study:

• To evaluate the outcomes of infants with rhabdomyosarcoma treated with proton therapy.
• To assess the efficacy and toxicity of proton therapy in this pediatric population.

Main Methods:

• A cohort of 37 infants under 24 months with non-metastatic rhabdomyosarcoma received proton therapy between 2009 and 2019.
• Local control (LC), progression-free survival (PFS), and overall survival (OS) were analyzed using Kaplan-Meier methods.
• Toxicity was graded according to CTCAEv5.0 criteria.

Main Results:

• At a median follow-up of 5.1 years, 5-year LC, PFS, and OS rates were 83%, 78%, and 83%, respectively.
• Unfavorable primary sites and nasal ala primaries were associated with inferior outcomes.
• Late grade 3 toxicity occurred in 6 infants; no grade 4 or 5 toxicity was observed.

Conclusions:

• Infants with rhabdomyosarcoma can achieve favorable outcomes with proton therapy, suggesting young age may not be an adverse prognostic factor with appropriate local treatment.
• Nasal ala primary tumors should be reclassified as unfavorable sites to improve risk stratification and treatment planning.