Pediatric Cancer

PV QA 3 - Poster Viewing Q&A 3

TU_25_3109 - Efficacy of Proton Therapy on Locoregional Control in Neuroblastoma

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

Efficacy of Proton Therapy on Locoregional Control in Neuroblastoma
A. Bagley1, D. R. Grosshans2, N. Philip1, M. F. McAleer1, S. L. McGovern3, J. Foster4, A. Mahajan5, and A. C. Paulino3; 1Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 2University of Texas MD Anderson Cancer Center, Houston, TX, 3The University of Texas MD Anderson Cancer Center, Houston, TX, 4Texas Children's Hospital, Houston, TX, 5Department of Radiation Oncology, Mayo Clinic, Rochester, MN

Purpose/Objective(s): Proton therapy is currently used in the management of many pediatric tumors to decrease late toxicities. However, one of the criticisms of proton therapy is the limited data regarding efficacy on disease control. The purpose of this study was to examine the locoregional and distant control rates after proton therapy for neuroblastoma.

Materials/Methods: A review of pediatric patients with neuroblastoma treated from 2007 to 2016 with proton therapy to the primary tumor and metastatic sites was performed. Patients had to be treated with curative intent with a minimum 12mo follow-up. The primary site and any MIBG-avid metastatic sites after induction therapy were treated. Locoregional control (LRC), irradiated distant site control (IDSC), progression-free survival (PFS), and overall survival (OS) were calculated using the Kaplan-Meier method. Outcomes were calculated as the time from diagnosis to first relapse or progression within the high-dose field of the primary (LRC) and irradiated metastatic site (IDSC), at any site (PFS), and to death from any cause (OS). Statistical analysis was performed using commercial scientific 2D graphing and statistics software.

Results: Fifteen patients with median age at diagnosis of 2 years (range 2 months – 5 years) were treated with proton therapy. Median follow-up was 4 years. 93% of patients had high-risk and 7% intermediate-risk neuroblastoma (International Neuroblastoma Staging System Stage IV 73%, Stage III 20%, Stage IIB 7%). Primary tumor sites included the retroperitoneum/abdomen (80%) and thorax (20%). All primary and 17 metastatic sites were irradiated. The number of irradiated metastatic sites was 0 in 5 patients, 1 in 5 patients, 2 in 3 patients, and 3 in 2 patients. The mean radiation doses to the primary and metastatic sites were 23.1 CGE (range 21.0 – 35.4) and 22.2 CGE (range 20.0 – 25.3). Mean doses to the heart, lungs, liver, and kidneys were 1.6, 3.6, 3.4, and 10.4 CGE, respectively. At both 2- and 5-years, LRC and IDSC rates were 93% and 90%, respectively. Driven primarily by progressive disease in non-irradiated metastatic sites, the 2- and 5-year PFS rates were 80% and 35%, while the 2- and 5-year OS were 87%. No radiation-related nephropathy or hepatopathy was reported.

Conclusion: Excellent locoregional and local control was achieved using proton therapy to the primary and post-induction MIBG positive distant sites. The predominant site of failure is distant progression in post-induction non-MIBG avid distant sites. While proton therapy provides high rates of local control with acceptable toxicity for neuroblastoma, further advances in systemic therapy are needed for improved control of systemic disease.

Author Disclosure: A. Bagley: None. D.R. Grosshans: None. M. McAleer: None. S.L. McGovern: Independent Contractor; MD Anderson Physicians Network. Honoraria; American College of Radiology. Travel Expenses; American College of Radiology. A. Mahajan: Secretary; PTCOG-NA. Membership; PROS. A.C. Paulino: Royalties for text book; Elsevier Inc. Committee Member; ABR.

Alexander Bagley, MD, PhD

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