SESSION TITLE: Cancer Student/Resident Case Report Posters II
SESSION TYPE: Medical Student/Resident Case Report
PRESENTED ON: Tuesday, October 28, 2014 at 01:30 PM - 02:30 PM
INTRODUCTION: Stereotactic Body Radiation Therapy (SBRT) delivers a high dose of radiation to a small volume over limited fractions. It is a viable treatment for localized lung cancer and oligometistatic pulmonary disease in adults, however, its role is not known in the pediatric population.
CASE PRESENTATION: T.S. is a 14-year-old boy, diagnosed with Ewing's Sarcoma of the left acetabulum with pulmonary metastases. He was enrolled on COG #AEWS0331 and randomized to induction chemotherapy, radiation to the hip and autologous peripheral blood stem cell transplant (SCT) using busulfan and melphalan for conditioning. T.S. recurred with multiple pulmonary metastases six months following SCT. He then received 12 cycles of chemotherapy with improvement of his pulmonary disease burden but had a residual metabolically active lesion on PET/CT. Surgery was considered, but there was concern about possible complications that could delay the planed salvage bone marrow transplant. SBRT was used to allow T.S. to receive a salvage transplant quickly with a low disease burden. A 4D-CT was obtained for treatment planning, PET/CT scan was fused, and an internal target volume (ITV) was delineated. A 5mm margin was placed around the ITV to account for set-up error. Organs at risk including the chest wall, contralateral lung, heart, and spinal cord were identified and contoured as avoidance structures. The patient was treated to a total dose of 3,600 cGy in three fractions over the course of five days using 6MV photons. The volume of lung receiving 2,000cGy and 500cGy were 6% and 30% respectively. T.S. tolerated SBRT well and successfully received his salvage transplant, however two months later developed a dry cough. CT demonstrated irregular ground glass opacities in the treatment field corresponding to the lower isodose clouds, consistent with radiation pneumonitis. The lesion itself had markedly improved.
DISCUSSION: While this case demonstrates an exciting application of SBRT in the pediatric patient, it also raises two important issues. In contrast to adults, children with metastatic disease often receive higher intensity chemotherapy, such as busulfan, which is known to sensitize the lungs to radiation damage . Additionally, as focal radiation treatments become more common in children, physicians must be aware of potential radiation induced toxicity such as the radiation pneumonitis experienced by T.S.
CONCLUSIONS: SBRT may offer a useful alternative to surgery to reduce intra-thoracic disease burden prior to myeloablative chemotherapy and stem cell transplant. However, there is potential for pulmonary toxicity, especially in the background of previous administration of pulmonary toxic drugs such as busulfan.
Reference #1: Bolling T, Dirksen U, Ranft A, et al. Radiation toxicity following busulfan/melphalan high dose chemotherapy in the Euro-Ewing-99-trial. Strahlenther Onol. 2009;185:21-22.
DISCLOSURE: The following authors have nothing to disclose: Mark Amsbaugh, Matthew Bertke, Alexandra Cheerva, Craig Silverman
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