(P086) Proton vs Photon/Electron-Based Therapy in the Treatment of Pediatric Salivary Gland Tumors: A Comparison of Dosimetric Data and Acute Toxicities

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OncologyOncology Vol 29 No 4_Suppl_1
Volume 29
Issue 4_Suppl_1

This report of adjuvant RT for pediatric salivary gland tumors is one of the largest to date and the only one to document outcomes following proton therapy. Compared with conventional photon/electron-based therapy, proton therapy significantly reduced doses to multiple normal tissues. Moreover, clinically, no grade 3 toxicities were observed in the proton group vs 45% in the photon/electron cohort. Continued follow-up is required to determine long-term outcomes.

Stephen R. Grant, BS, David R. Grosshans, MD, PhD, Anita Mahajan, MD; Baylor College of Medicine; Department of Radiation Oncology, UT MD Anderson Cancer

PURPOSE: Adjuvant radiotherapy (RT) is frequently indicated for high-risk salivary gland tumors. For pediatric patients, minimizing radiation to surrounding normal tissues is of particular importance. We retrospectively compared clinical outcomes and toxicity profiles for pediatric patients with parotid and submandibular tumors treated with either adjuvant proton- or photon/electron-based RT.

MATERIALS AND METHODS: We retrospectively identified all patients aged ≤ 18 years treated with radiation for salivary gland tumors between 1996 and 2014 at our institution. Demographic, disease-control, and survival data were recorded, and dosimetric data were compiled. Toxicities were scored according to National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events version 4.0 (CTCAE 4.0) criteria. Statistical analyses were performed using GraphPad Prism, with two-sided t-tests determined to be significant when P < .05.

RESULTS: A total of 24 pediatric patients treated with adjuvant RT were identified (20 parotid, 4 submandibular). Histologies included mucoepidermoid carcinoma (12), adenoid cystic carcinoma (5), adenocarcinoma (2), acinic cell carcinoma (2), myoepithelioma (1), undifferentiated carcinoma (1), and pleomorphic adenoma (1). A total of 13 patients received proton therapy, and 11 received photon/electron-based therapy. The mean prescribed dose was 60 Gy in each cohort (range: 54–66 Gy). No acute grade 3 dermatitis or mucositis was seen in the proton cohort vs 27% and 18% in the photon/electron cohort, respectively. Significantly greater weight loss was reported in those receiving photon/electron radiotherapy (median 5.2% vs 0%), with one patient requiring placement of a feeding tube (compared with none in the proton cohort). With a mean follow-up of 49 months (range: 2 mo–18 yr), no disease recurrence or deaths were observed in either cohort. Compared with photon/electron-based therapy, proton therapy was associated with significantly lower mean doses to the spinal cord (0.2 Gy vs 19 Gy), pituitary gland (0.0 Gy vs 5.7 Gy), optic nerves (0.0 Gy vs 3 Gy), oral cavity (4.6 Gy vs 19 Gy), thyroid gland (1.5 Gy vs 24 Gy), larynx (11 Gy vs 39 Gy), and contralateral structures, including the eye (0.0 Gy vs 1.4 Gy), mandible (0.0 Gy vs 7.7 Gy), and parotid (0.0 Gy vs 5.2 Gy) and submandibular glands (0.0 Gy vs 8.1 Gy) (all P < .05).

CONCLUSION: This report of adjuvant RT for pediatric salivary gland tumors is one of the largest to date and the only one to document outcomes following proton therapy. Compared with conventional photon/electron-based therapy, proton therapy significantly reduced doses to multiple normal tissues. Moreover, clinically, no grade 3 toxicities were observed in the proton group vs 45% in the photon/electron cohort. Continued follow-up is required to determine long-term outcomes. 

Proceedings of the 97th Annual Meeting of the American Radium Society- americanradiumsociety.org

Articles in this issue

(P005) Ultrasensitive PSA Identifies Patients With Organ-Confined Prostate Cancer Requiring Postop Radiotherapy
(P001) Disparities in the Local Management of Breast Cancer in the United States According to Health Insurance Status
(P002) Predictors of CNS Disease in Metastatic Melanoma: Desmoplastic Subtype Associated With Higher Risk
(P003) Identification of Somatic Mutations Using Fine Needle Aspiration: Correlation With Clinical Outcomes in Patients With Locally Advanced Pancreatic Cancer
(P004) A Retrospective Study to Assess Disparities in the Utilization of Intensity-Modulated Radiotherapy (IMRT) and Proton Therapy (PT) in the Treatment of Prostate Cancer (PCa)
(S001) Tumor Control and Toxicity Outcomes for Head and Neck Cancer Patients Re-Treated With Intensity-Modulated Radiation Therapy (IMRT)-A Fifteen-Year Experience
(S003) Weekly IGRT Volumetric Response Analysis as a Predictive Tool for Locoregional Control in Head and Neck Cancer Radiotherapy 
(S004) Combination of Radiotherapy and Cetuximab for Aggressive, High-Risk Cutaneous Squamous Cell Cancer of the Head and Neck: A Propensity Score Analysis
(S005) Radiotherapy for Carcinoma of the Hypopharynx Over Five Decades: Experience at a Single Institution
(S002) Prognostic Value of Intraradiation Treatment FDG-PET Parameters in Locally Advanced Oropharyngeal Cancer
(P006) The Role of Sequential Imaging in Cervical Cancer Management
(P008) Pretreatment FDG Uptake of Nontarget Lung Tissue Correlates With Symptomatic Pneumonitis Following Stereotactic Ablative Radiotherapy (SABR)
(P009) Monte Carlo Dosimetry Evaluation of Lung Stereotactic Body Radiosurgery
(P010) Stereotactic Body Radiotherapy for Treatment of Adrenal Gland Metastasis: Toxicity, Outcomes, and Patterns of Failure
(P011) Stereotactic Radiosurgery and BRAF Inhibitor Therapy for Melanoma Brain Metastases Is Associated With Increased Risk for Radiation Necrosis
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