Pediatric Cancer

PV QA 3 - Poster Viewing Q&A 3

TU_25_3114 - Long-term outcomes of radiation therapy (RT) in the management of malignant peripheral nerve sheath tumors (MPNST) in patients with neurofibromatosis type 1 (NF1)

Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3

Long-term outcomes of radiation therapy (RT) in the management of malignant peripheral nerve sheath tumors (MPNST) in patients with neurofibromatosis type 1 (NF1)
L. Sloan1, S. A. Terezakis1, J. O. Blakeley2,3, B. Slobogean2,3, and L. R. Kleinberg4; 1The Johns Hopkins Hospital, Department of Radiation Oncology and Molecular Radiation Sciences, Baltimore, MD, 2The Johns Hopkins Hospital, Johns Hopkins Comprehensive Neurofibromatosis Center, Baltimore, MD, 3The Johns Hopkins Hospital, Department of Neurology, Baltimore, MD, 4Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD

Purpose/Objective(s): NF1 is an autosomal dominant tumor predisposition syndrome. Malignant peripheral nerve sheath tumor (MPNST) is a rare sarcoma subtype that is the leading cause of death in people with NF1. There is limited information regarding outcomes of patients with NF1-associated MPNST, and specifically after radiation therapy (RT), a modality known to infrequently cause second cancers. As it is important to identify outcomes to aid in the selection of an optimal treatment paradigm for patients, our primary objective is to determine the local control (LC) rate in patients with NF1 who develop MPNST and are treated with RT. We also assessed overall survival (OS) and frequency of CTCAE toxicities following RT. We hypothesize that RT is an effective and safe treatment modality in patients with NF1 with MPNST.

Materials/Methods: Data were collected through retrospective analysis of records of patients treated at our institution with the diagnosis of NF1 and pathologically-confirmed MPNST who underwent definitive RT from 2009-2017. Patients without follow-up or that had a history of previous RT to the affected area were excluded. Kaplan–Meier curves were used to estimate LC and OS rates.

Results: 15 patients (F=9, M=6) were identified with median age of 25 (range 10-38) years. The median follow-up was 29.1 (9.9-84.5) months. 47% of patients had tumors located in an extremity and 53% within the trunk. Four MPNSTs were <5 cm (27%), five 5-10 cm (33%) and six >10 cm (40%). All patients received initial therapy for a new diagnosis of MPNST, except one treated for recurrent disease after resection only. Patients were treated with several paradigms: 13% surgery + adjuvant RT, 33% surgery + adjuvant systemic therapy (ST) and RT, 40% neoadjuvant ST and RT + surgery, 7% interdigitated chemotherapy and neoadjuvant RT + surgery, 7% ST and RT. The median RT dose delivered was 50 Gy (44-63 Gy) via IMRT (87%), SBRT (7%), or 3D (7%). LC was estimated to be 100%, 91.7%, and 91.7% at 1, 3, and 5 years, and OS was identified as 100%, 79.2%, and 53.2% at 1, 3, and 5 years, respectively. Three patients progressed distantly (brain=2, lungs=1) and two developed second primaries (second MPNST, gliosarcoma). The most common toxicities at the end of RT were grade 1 fatigue and grade 1 pain (Table 1). No secondary malignancies within the radiation field were reported.

Conclusion: In our study, therapeutic strategies that include RT resulted in excellent LC rates and were well tolerated for NF1-associated MPNST. Given the paucity of data about safety and efficacy of RT for NF1-associated MPNST, this dataset is encouraging, as outcomes were comparable to those reported for other types of soft tissue sarcomas. However, longer duration follow-up and larger cohorts are required to characterize the risk of second tumors and develop optimal approaches regarding timing and RT delivery.
No. of Pts with CTCAE Toxicity (Grade)
1 2 3 4 5
Fatigue 7 3 0 0 0
Pain 7 4 0 0 0
Dermatitis 3 3 0 0 0
Paresthesia 1 0 0 0 0
Anorexia 3 0 1 0 0
Diarrhea 1 0 0 0 0
Dysphagia 1 0 0 0 0
Nausea 2 1 1 0 0
Vomiting 1 1 1 0 0

Author Disclosure: L. Sloan: Employee; Einstein Healthcare Network. S.A. Terezakis: Research Grant; Elekta. Chair; Pediatric Scientific Committee at ASTRO. J.O. Blakeley: None. B. Slobogean: None. L.R. Kleinberg: Research Grant; Arbor Pharmaceutical, Novocure, Inc, Accuray, Inc. Honoraria; Accuray, Inc.

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TU_25_3114 - Long-term outcomes of radiation therapy (RT) in the management of malignant peripheral nerve sheath tumors (MPNST) in patients with neurofibromatosis type 1 (NF1)



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