C. Jiang1, C. Mogilevsky2, G. Kurtz1, T. Laetsch3, N. Balamuth3, J. W. Stern3, T. F. Jubilirer3, R. B. Womer3, E. R. Cummings4, S. Fuller5, P. Mattei6, and C. E. Hill-Kayser4; 1Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, 2Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 3Division of Oncology, Childrens Hospital of Philadelphia and Abramson Cancer Center, University of Pennsylvania, Philadelphia, PA, 4Department of Radiation Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 5Division of Cardiothoracic Surgery, Childrens Hospital of Philadelphia and Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 6Division of General, Thoracic and Fetal Surgery, Childrens Hospital of Philadelphia and Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
Purpose/Objective(s): Pediatric sarcomas of the chest wall and mediastinum are rare, and classic management paradigms for localized disease involve chemotherapy followed by maximal safe resection. Post-operative radiotherapy (RT) is indicated for residual disease, but options after large-volume resection may be limited by the presence of lung tissue and other organs at risk (OAR) within the target volume. Pre-operative RT may thus be appealing, but is rarely employed largely due to toxicity risk, which may be mitigated with the use of proton therapy. We report clinical, treatment, and dosimetric details for 5 pediatric patients with localized, bulky primary thoracic sarcomas who underwent a multimodality treatment approach including pre-operative proton RT. Materials/
Methods: This is a retrospective case series from a single institution. Clinical and dosimetric details were extracted from the patient charts. Acute toxicities were graded per the Common Terminology Criteria for Adverse Events (CTCAE) version 5. Descriptive statistics were used to report on outcomes. Median follow-up was measured from time of surgery. Results: Of the 5 patients, 3 had synovial sarcoma and 1 each had Ewing sarcoma and undifferentiated spindle cell sarcoma. Median age was 12 years (range 3-17) and all were male. The maximum tumor dimension along a single axis ranged from 10.1-19.0 cm (mean 14.1 cm), and 3 tumors were left-sided. All patients underwent neoadjuvant chemotherapy followed by preoperative RT with pencil beam scanning (PBS), to a median total dose of 50 Gray equivalents (GyE) (range 45.6-50 GyE). This was followed by maximal safe resection within 4-6 weeks, after which 3 patients received adjuvant proton RT for close or positive margins to a median of 16 GyE. Mean doses achieved to adjacent OARs include: heart V20 (volume receiving 20 GyE; 42%), heart V5 (69%), ipsilateral lung V20 (95%), contralateral lung V20 (5%), ipsilateral lung mean (45.2 GyE), contralateral lung mean (3.8 GyE), esophagus mean (30.9 GyE), and spinal cord Dmax (maximum dose; 43.6 GyE). The average dose to 95% of the planning target volume (PTV D95%) was 95% of the prescription dose. Two grade 3 toxicities (dermatitis and anorexia) were observed; no grade 4-5 events were observed. No patient experienced symptomatic pneumonitis. With a median follow-up of 30.2 months (range 15.8-59 months), no patient has experienced local recurrence; 4 are alive (3 disease-free and 1 with metastatic disease). The final patient died from metastatic disease. Mean time to metastasis was 15.5 months. Scoliosis was reported in 3 patients; none required treatment. No other late RT sequelae, including cardiopulmonary toxicities or secondary malignancies, were reported. Conclusion: For patients with bulky but localized sarcomas of the thorax, pre-operative RT is a viable option for management and long-term disease control. Proton therapy has promising applications in this area, particularly in achieving near complete sparing of the contralateral lung.
