Rhabdomyosarcoma in Pediatric Patients Under 2 Years: Clinical Features and Outcome.

Background: Rhabdomyosarcoma (RMS) typically responds well to a combination of treatments with favorable prognosis in children 1 to 9 years old. However, infants may fare worse due to receiving less aggressive local therapy for concerns about long-term effects of surgery/radiation. This study investigates the clinical characteristics, treatment approach, and survival outcomes of RMS in children under 2.

Methods: We reviewed retrospectively children younger than 2 years with newly diagnosed RMS treated from January 2002 until December 2022 at King Hussein Cancer Center. Demographics, clinical characteristics, and outcomes were analyzed. Statistical analysis included descriptive statistics and survival analysis using Kaplan-Meier methods. All cases were reviewed in a multidisciplinary clinic comprising experienced radiotherapists and surgeons.

Results: We identified 34 cases of RMS in patients younger than 2 years at diagnosis. The median age was 13 months, with 70.6% males. The most common tumor site was bladder/prostate (N=13, 38%), followed by orbit (N=5, 14.7%), the predominant subtype was embryonal (N=30). Risk-stratification categorized 17.6% as low-risk and 79.4% as intermediate-risk. Twenty-five patients had tumors >5 cm, with metastasis in 6 (17.6%). All patients received neo-adjuvant chemotherapy, local control was by radiotherapy only (n=12, 35.3%), combined surgery and radiotherapy (n=11, 32.4%), or surgery alone (n=3, 8.8%). The 5-year event-free and overall survival rates were 55.1% and 57.5%, respectively. Fourteen patients experienced relapse/progression, with local relapse the most common pattern. TNM stage, clinical group, metastasis at diagnosis, and radiotherapy use significantly impacted survival.

Conclusions: Children under 2 years of age with RMS face significant challenges, with high local recurrence rates and suboptimal survival outcomes compared with older pediatric patients. Our findings highlight the need for tailored treatment approaches that balance effective local control with minimizing long-term toxicity.