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Proton beam therapy for retroperitoneal neuroblastoma
Reporter: J. Taylor Whaley, MD
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: May 12, 2011
Presenter: Hiroshi Fuji, M.D.
- Neuroblastoma is the most common extracranial solid tumor malignancy in children and the most common malignancy in infants less than 1 year old.
- Neuroblastoma most commonly arises in the adrenal gland, followed by the abdominal cavity.
- Radiation therapy is associated with GI and renal toxicities and is known to increase the risk of second malignancies and musculoskeletal complications in long term survivors.
- The goal of the majority of new pediatric cancer protocols are aimed at diminishing both acute side effects as well as long term sequelae.
- The purpose of this study was to explore the potential advantage to reduce acute toxicity in patients with retroperitoneal neuroblastoma treated with proton beam therapy.
- Six patients with high-risk abdominal neuroblastoma were treated with proton beam therapy.
- Retrospective review of these 6 patients was performed, with analysis of dosimetry and acute toxicities.
- Clinical target volume included tumor bed in the post-op setting or gross tumor in the recurrent setting.
- The dose-volume calculations were compared for proton beam therapy with traditional AP/PA photon therapy.
- All patients included in the retrospective evaluation were high risk with age ranging from 34 months to 4 years.
- Site of tumor included paraspinal lesions in 3 patients, left retroperitoneum in 2 patients, and right retroperitoneum in 1 patient.
- Median follow up was 12 months.
- Dose prescriptions ranged from 21.6 to 41.4 Gy (RBE) in 12 to 20 fractions.
- Number of fields used in treatment planning ranged from 3 to 5.
- V20 (volume receiving 20 Gy) for the right kidney, left kidney, and liver for proton therapy were 14%, 18%, and 26% lower than photon planning, respectively.
- Mean dose of involved vertebral bone and stomach in proton therapy were significantly lower than photon planning at 9.6 Gy (RBE) and 8.0 Gy (RBE), respectively.
- Integral dose to the patient was 51% lower for proton therapy.
- No GI toxicity was observed in any patient.
- Myelosuppresion was observed in 4 patients; however, 3 patients had received a bone marrow transplant and one received concurrent chemotherapy, likely confounding this result.
- In pediatric patients with neuroblastomas, proton therapy offers a viable option and advantage in reduction of organ injury and integral dose to the patient.
- Proton therapy was associated with decreased dose to the abdominal organs compared to traditional AP/PA fields and symmetric irradiation of the vertebral bodies remained achievable.
- Acute toxicity in this cohort of patients was acceptable.
- Further follow up is required to evaluate the delayed side effects of proton therapy
- The authors present their experience with neuroblastoma treated with proton radiotherapy, and the presentation is certainly a valuable contribution to the literature.
- In the small cohort of patients presented, delivery of proton beam radiotherapy for treatment of neuroblastoma appears to be feasible. It should be noted that treatment of abdominal tumors is very complex and each case must be evaluated on an individual basis.
- It should be noted that the photon planning used for dosimetric comparison used only tradition AP/PA fields and did not incorporate IMRT, which is commonly used for treatment of abdominal neuroblastoma.
- These findings demonstrate that proton radiation may be a treatment technique offering improved dosimetry with reasonable acute toxicities in this difficult subset of patients.
- The additional decreased integral dose of radiation may prove to be particularly helpful in reducing second malignancies; however, additional follow up is needed to validate this possibility.
- Information on late effects and long term outcomes associated with this treatment remains unavailable and will greatly contribute to the literature when longer follow-up permits analysis of quality of life following proton beam radiotherapy as opposed to photon-based treatment delivery.
- Certainly, prospective randomized trials are needed to further evaluate the role of proton therapy in abdominal neuroblastoma.