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Volumetric considerations in radiotherapy for pediatric parameningeal rhabdomyosarcomas
Changhu Chen1, Hui Kuo G Shu, Joel W Goldwein
1Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA 19104, USA. maity@mail.med.upenn.edu
Insights
Radiation volume did not significantly impact outcomes for pediatric parameningeal rhabdomyosarcomas (PM-RMS). Shrinking field radiotherapy with a boost to the post-chemotherapy tumor volume proved effective, offering comparable results to treating the entire pre-chemotherapy volume.
Area of Science:
- Pediatric Oncology
- Radiation Oncology
- Medical Physics
Background:
- Parameningeal rhabdomyosarcomas (PM-RMS) are rare childhood cancers.
- Optimizing radiation therapy volume is crucial for balancing treatment efficacy and minimizing late effects in pediatric patients.
Purpose of the Study:
- To evaluate the impact of radiation therapy volume on treatment outcomes in pediatric PM-RMS.
- To compare outcomes between shrinking field radiotherapy and conventional volume irradiation.
Main Methods:
- Retrospective analysis of 30 pediatric patients with PM-RMS treated between 1988 and 1999.
- Patients received multi-agent chemotherapy and external beam radiotherapy.
- Two radiation techniques were compared: initial large volume irradiation versus shrinking field with a post-chemotherapy tumor volume boost.
Main Results:
- Overall survival, progression-free survival, and local control rates were 82%, 76%, and 76%, respectively.
- Histologic type, tumor size, and age were predictive of survival and local control.
- No significant difference in outcomes was observed between the shrinking field and conventional volume irradiation groups.
Conclusions:
- Shrinking field radiotherapy with a boost to the post-chemotherapy tumor volume is an effective treatment for pediatric PM-RMS.
- This technique yields outcomes comparable to treating the entire pre-chemotherapy tumor volume.
- Tailored radiation fields may reduce late treatment-related toxicities and warrant further investigation.
Purpose:
To assess the influence of radiation volume on outcome in pediatric parameningeal rhabdomyosarcomas (PM-RMSs).
Methods And Materials:
Thirty patients ranging in age from 2 to 18 years (median 6) with PM-RMS were treated at the Hospital of the University of Pennsylvania and the Children's Hospital of Philadelphia between August 1988 and December 1999. The histologic subtypes included embryonal (n = 26), alveolar (n = 3), and undifferentiated (n = 1). Twenty-seven patients had Group III and three had Group IV disease. Twenty-seven patients underwent biopsy only and three subtotal resection. All patients were treated with multiple-agent chemotherapy and external beam radiotherapy. In 8 patients, all of whom had intracranial tumor extension, the tumor and whole brain were treated as the initial volume. In the remaining patients, most of those treated before 1992 were treated to the prechemotherapy (CMT) tumor volume for the entire treatment up to the total dose, which ranged from 45 to 59.4 Gy (median dose 57.9). In contrast, patients treated after 1992 generally received radiation initially to the pre-CMT volume (30.6-40 Gy; median dose 36) followed by a conedown to the post-CMT volume to a final dose of 41.4-55.2 Gy (median 50.4).
Results:
With a median follow-up of 6.2 years (range 2.1-13.3), the actuarial 5-year overall survival, progression-free survival, and local control rate for the entire group was 82%, 76%, and 76%, respectively. Seven failures and five deaths have been documented. In univariate analysis, histologic type, tumor size, and age at diagnosis were found to be predictive of overall survival and local control. No statistically significant difference in overall survival or local control was seen between patients who received a conedown to the post-CMT volume (n = 13) and patients in whom the pre-CMT volume was included for the entire treatment (n = 9).
Conclusion:
Radiotherapy delivered to children with PM-RMS using a shrinking field technique with a post-CMT volume boost was effective and appears to give results comparable to those of patients in whom the pre-CMT volume was treated for the entire course. The use of such tailored treatment fields is likely to lead to fewer late effects and warrants further investigation.