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Int J Radiat Oncol Biol Phys. 2018 May 1;101(1):152-168. doi: 10.1016/j.ijrobp.2018.01.013.

National Cancer Institute Workshop on Proton Therapy for Children: Considerations Regarding Brainstem Injury.

Author information

1
Department of Radiation Oncology, Harvard Medical School and Brigham and Women's Hospital, Dana-Farber Cancer Institute, Boston Children's Hospital, Boston, Massachusetts.
2
Department of Radiation Oncology, University of Florida, Jacksonville, Florida.
3
Department of Radiation Oncology, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts.
4
Department of Radiation Oncology, Winship Cancer Institute, Emory University, Atlanta, Georgia.
5
Department of Radiation Oncology, MD Anderson Cancer Center, Houston, Texas; Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
6
Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
7
Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas.
8
Department of Radiation Oncology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.
9
Department of Radiation Oncology, Johns Hopkins Medical Institute, Baltimore, Maryland.
10
Department of Radiation Oncology, Harvard Medical School and Dana-Farber Cancer Institute, Boston, Massachusetts.
11
Department of Radiation Oncology, University of California, San Francisco, San Francisco, California.
12
Department of Radiology, Harvard Medical School and Dana-Farber Cancer Institute, Boston Children's Hospital, Boston, Massachusetts.
13
Department of Pediatrics, Johns Hopkins Medical Institute, Baltimore, Maryland.
14
Department of Radiation Oncology, UMass Memorial Medical Center, Worcester, Massachusetts.
15
Northwestern Medicine Chicago Proton Center, Chicago, Illinois.
16
Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, Colorado.
17
Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri.
18
Children's Hospital of Angeles and University of Southern California Keck School of Medicine, Los Angles, California.
19
Radiation Research Program, National Cancer Institute, National Institutes of Health, Rockville, Maryland.
20
Department of Radiation Oncology, University of Texas Southwestern Medical School, Dallas, Texas. Electronic address: larry.kun@utsouthwestern.edu.

Abstract

PURPOSE:

Proton therapy can allow for superior avoidance of normal tissues. A widespread consensus has been reached that proton therapy should be used for patients with curable pediatric brain tumor to avoid critical central nervous system structures. Brainstem necrosis is a potentially devastating, but rare, complication of radiation. Recent reports of brainstem necrosis after proton therapy have raised concerns over the potential biological differences among radiation modalities. We have summarized findings from the National Cancer Institute Workshop on Proton Therapy for Children convened in May 2016 to examine brainstem injury.

METHODS AND MATERIALS:

Twenty-seven physicians, physicists, and researchers from 17 institutions with expertise met to discuss this issue. The definition of brainstem injury, imaging of this entity, clinical experience with photons and photons, and potential biological differences among these radiation modalities were thoroughly discussed and reviewed. The 3 largest US pediatric proton therapy centers collectively summarized the incidence of symptomatic brainstem injury and physics details (planning, dosimetry, delivery) for 671 children with focal posterior fossa tumors treated with protons from 2006 to 2016.

RESULTS:

The average rate of symptomatic brainstem toxicity from the 3 largest US pediatric proton centers was 2.38%. The actuarial rate of grade ≥2 brainstem toxicity was successfully reduced from 12.7% to 0% at 1 center after adopting modified radiation guidelines. Guidelines for treatment planning and current consensus brainstem constraints for proton therapy are presented. The current knowledge regarding linear energy transfer (LET) and its relationship to relative biological effectiveness (RBE) are defined. We review the current state of LET-based planning.

CONCLUSIONS:

Brainstem injury is a rare complication of radiation therapy for both photons and protons. Substantial dosimetric data have been collected for brainstem injury after proton therapy, and established guidelines to allow for safe delivery of proton radiation have been defined. Increased capability exists to incorporate LET optimization; however, further research is needed to fully explore the capabilities of LET- and RBE-based planning.

PMID:
29619963
PMCID:
PMC5903576
DOI:
10.1016/j.ijrobp.2018.01.013
[Indexed for MEDLINE]
Free PMC Article

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