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Updated: Dec 29, 2025
Proton Therapy Delivery and Its Clinical Application in Select Solid Tumor Malignancies
Published on: February 6, 2019
Outcomes Following Proton Therapy for Group III Pelvic Rhabdomyosarcoma
Daniel J Indelicato1, Ronny L Rotondo1, Matthew J Krasin2
1Department of Radiation Oncology, College of Medicine, University of Florida, Jacksonville, Florida.
Insights
Proton therapy for pediatric pelvic rhabdomyosarcoma (RMS) shows promising outcomes, with high local control and survival rates. This treatment approach in young children with large tumors offers reduced toxicity and potential for bladder preservation.
Area of Science:
- Pediatric Oncology
- Radiation Oncology
- Medical Physics
Background:
- Rhabdomyosarcoma (RMS) is a rare pediatric cancer.
- Pelvic RMS presents unique treatment challenges due to proximity to vital organs.
- Proton therapy offers a more targeted radiation approach compared to traditional photon therapy.
Purpose of the Study:
- To evaluate the institutional outcomes of proton therapy for pediatric pelvic rhabdomyosarcoma (RMS).
- To assess local control, progression-free survival, and overall survival rates.
- To analyze treatment-related toxicities and functional outcomes, particularly bladder preservation.
Main Methods:
- A prospective outcome study included 31 children (≤21 years) with group III pelvic RMS treated between 2007-2018.
- Patients received multi-agent chemotherapy followed by proton therapy (median dose 50.4 Gy RBE).
- Surgical interventions, including resection and cystectomy, were analyzed alongside outcomes.
Main Results:
- Five-year local control, progression-free survival, and overall survival rates were 83%, 80%, and 84%, respectively.
- Younger patients (<3 years) demonstrated significantly better local control (100% vs 68%, P=.02).
- Embryonal histology was associated with improved survival (96% vs 54%, P=.02); urinary toxicity was minimal except after cystectomy.
Conclusions:
- Proton therapy for pediatric pelvic RMS yields comparable local control to historical data with reduced toxicity.
- Functional bladder preservation is achievable in a majority of patients.
- Caution is advised for exploratory biopsies within 18 months post-radiation due to potential toxicity.
Purpose:
This study aimed to report on the institutional outcomes after proton therapy for pelvic rhabdomyosarcoma (RMS).
Methods And Materials:
Thirty-one children (≤21 years old) with group III pelvic RMS were enrolled on a prospective outcome study and treated between 2007 and 2018. Patients with vaginal/cervical RMS were excluded. The median age was 2.6 years. Twenty-four patients had embryonal RMS. At diagnosis, the median tumor volume was 185 cm3 and the median maximum diameter was 9.4 cm. Seven patients had N1 disease. Nineteen and 12 patients received European Pediatric Soft Tissue Sarcoma Study Group- and Children's Oncology Group-based chemotherapy, respectively. Fourteen patients underwent resection of the primary tumor after induction chemotherapy, including 6 patients who had a total cystectomy. The median radiation dose was 50.4 Gy relative biological effectiveness.
Results:
With a median follow-up of 4.2 years, the 5-year local control, progression-free survival, and overall survival rates were 83%, 80%, and 84%, respectively. Patients <3 years old had better local control (100% vs 68%; P = .02), and patients with embryonal histology had better survival (96% vs 54%; P = .02). No other factors were significantly associated with disease control or survival. Specifically, no statistically significant difference was observed in local control, progression-free survival, or overall survival when comparing patients who underwent biopsy versus gross total resection (75% vs 93%, 68% vs 93%, 75% vs 93%, respectively). Excluding patients who underwent cystectomy, urinary toxicity was limited to 2 patients with nocturnal enuresis. Exploratory surgery to address a persistent mass or thickened bladder wall after radiation was the most common source of serious toxicity.
Conclusions:
This cohort of young children with large pelvic tumors treated with proton therapy demonstrates similar local control with less toxicity than historic reports. Functional bladder preservation is possible in most patients. Exploratory biopsy in the 18 months after radiation should be approached with caution.
