Jennifer Vogel

Purpose: Pediatric head and neck malignancies are managed with intensive multimodality therapy. Proton beam therapy (PBT) may reduce toxicity by limiting exposure of normal tissue to radiation. In this study, we report acute toxicities and early outcomes following PBT for pediatric head and neck malignancies.Materials and methods: Between 2010 and 2016, pediatric patients with nonhematologic malignancies of the head and neck were treated with PBT. Clinical and dosimetric data were abstracted from the medical record and treatment planning system with institutional review board approval.Results: Sixty‐nine consecutive pediatric patients were treated with proton‐based radiotherapy for head and neck malignancies. Thirty‐five were treated for rhabdomyosarcoma to a median dose of 50.4 Gy relative biological effectiveness [RBE]. Ten patients were treated for Ewing sarcoma to a median dose of 55.8 Gy[RBE]. Twenty‐four patients were treated for other histologies to a median dose of 63.0 Gy[RBE]. Grade 3 oral mucositis, anorexia, and dysphagia were reported to be 4, 22, and 7%, respectively. Actuarial 1‐year freedom from local recurrence was 92% (95% CI 80–97). Actuarial 1‐year overall survival was 93% (95% CI 79–98) in the entire cohort. Oral cavity mucositis was significantly correlated with oral cavity dose (D80 and D50 [P < 0.05], where D80 and D50 are dose to 50% of the volume and dose to 80% of the volume, respectively).Conclusions: In this study, we report low rates of acute toxicity in a cohort of pediatric patients with head and neck malignancies. PBT appears safe for this patient population, with local control rates similar to historical reports. Longer follow‐up will be required to evaluate late toxicity and long‐term disease control.

Background: While often managed with surgery alone, patients with thymic malignancies with high-risk features may benefit from adjuvant radiation therapy but are at risk for late toxicities. Previously, the risk of major cardiac events (MCEs) was reported to increase by 7% per one Gray (Gy) to the heart. In this study, we compare dose to organs at risk (OARs) with intensity-modulated (IMRT) versus proton beam therapy (PBT). We hypothesize a decrease risk of predicted MCEs with PBT. Material and methods: Patients requiring adjuvant therapy for thymic malignancies were treated with double scattered proton beam therapy (DS-PBT). Clinical backup IMRT plans were generated. Predicted MCEs were calculated based on median dose to the heart. A Wilcoxon rank sum test was used for statistical comparisons. Results: Twenty-two consecutive patients were evaluated. DS-PBT resulted in statistically significant decreases in dose to the heart, lungs, left ventricle, esophagus, and spinal cord (all p ≤ .01). The increase in risk of MCEs from 0 to ≥20 years was lower with PBT (74% versus 135%, p = .04). Discussion: DS-PBT results in decreased dose to OARs and may reduce the risk of MCEs compared with IMRT. Long-term follow-up is required to assess for clinical benefit from DS-PBT.

Background: Multimodality treatment for patients with Wilms tumor has improved patient survival, but is associated with acute and long‐term toxicity, partially due to irradiation. Proton therapy using pencil beam scanning (PBS) is a promising technique to reduce dose to organs at risk (OAR). In this study, we evaluate PBS plans for postoperative irradiation in patients with Wilms tumor.Procedure: Patients were treated with anterior‐posterior–posterior‐anterior (AP–PA) photon fields encompassing the preoperative tumor volume. Patients requiring whole lung irradiation were treated with AP–PA photon fields covering the bilateral lungs. Prescription doses were generally 1,080 and 1,200 cGy, respectively. Flank PBS plans encompassing the ipsilateral retroperitoneum and para‐arotic nodes were generated for dosimetric evaluation.Results: Treatment records and comparison plans of 11 patients were reviewed. Mean dose and median dose to 50% or more of the contralateral kidney (D50) were 135 cGy and 139 cGy with photons and 52 cGy relative biological effectiveness (RBE) (P = 0.009) and 5 cGy RBE (P = 0.000001) with PBS. Mean dose and median D50 to bowel was 639 cGy and 979 cGy with photons and 379 cGy RBE (P = 0.001) and 47 cGy RBE (P = 0.004) with PBS. Mean dose and median D50 to the liver were 755 cGy and 1,013 cGy with photons and 411 cGy RBE (P = 0.02) and 132 cGy RBE (P = 0.02) with PBS. For patients with right‐sided tumors, mean liver dose following sequential whole lung irradiation was 1,252 cGy with photons and 845 cGy RBE (P = 0.04) with PBS.Discussions: PBS proton therapy is a feasible method for irradiating the retroperitoneum and provides significant sparing of dose to critical OAR. This may translate to improved long‐term health outcomes for patients and warrants further clinical investigation.

Stereotactic radiosurgery (SRS) is an alternative to post-operative whole brain radiation therapy (WBRT) following resection of brain metastases. At our institution, CyberKnife (CK) is considered for local treatment of large cavities ≥2 cm. In this study, we aimed to evaluate patterns of failure and characterize patients best suited to treatment with this approach. We retrospectively reviewed 30 patients treated with CK to 33 resection cavities ≥2 cm between 2011 and 2014. Patterns of intracranial failure were analyzed in 26 patients with post-treatment imaging. Survival was estimated by the Kaplan-Meier method and prognostic factors examined with log-rank test and Cox proportional hazards model. The most frequent histologies were lung (43 %) and breast (20 %). Median treatment volume was 25.1 cm3 (range 4.7–90.9 cm3) and median maximal postoperative cavity diameter was 3.8 cm (range 2.8–6.7). The most common treatment was 30 Gy in 5 fractions prescribed to the 75 % isodose line. Median follow up for the entire cohort was 9.5 months (range 1.0–34.3). Local failure developed in 7 treated cavities (24 %). Neither cavity volume nor CK treatment volume was associated with local failure. Distant brain failure occurred in 20 cases (62 %) at a median of 4.2 months. There were increased rates of distant failure in patients who initially presented with synchronous metastases (p = 0.02). Leptomeningeal carcinomatosis (LMC) developed in 9 cases, (34 %). Salvage WBRT was performed in 5 cases (17 %) at a median of 5.2 months from CK. Median overall survival was 10.1 months from treatment. This study suggests that adjuvant CK is a reasonable strategy to achieve local control in large resection cavities. Patients with synchronous metastases at the time of CK may be at higher risk for distant brain failure. The majority of cases were spared or delayed WBRT with the use of local CK therapy.

Purpose: Pheochromocytomas (PCCs) are neuroendocrine tumors arising from the adrenal medulla or as paraganglioma (PGL) from extraadrenal sites. While usually benign, a small fraction are malignant. Multi-modality therapy is used in treating malignant disease; however, little data exists on the role of external beam radiation therapy (EBRT). In this retrospective review, we assessed response to EBRT in malignant PCCs or PGLs. Methods and Materials: Records of patients treated at the National Institutes of Health who received EBRT between 1990-2012 were studied. Patients were assessed for symptomatic control, biochemical response, local and distant control by response evaluation criteria in solid tumors (RECIST) v1.1 or stable disease on imaging reports, toxicity by radiation therapy oncology group (RTOG) criteria, and survival. Results: There were 24 patients treated who received EBRT to lesions of the abdomen (n=3), central nervous system (n=4), and bone (n=40). Lesions were treated with 3D conformal EBRT to a mean dose of 31.8 Gy in 3.3 Gy fractions, or fractionated stereotactic radiosurgery (FSRT) to 21.9 Gy in 13.6 Gy fractions. Patients experienced acute (n=15) and late (n=2) RTOG toxicities; no patient experienced acute toxicity ≥4 or late toxicity ≥2. Symptomatic control was achieved in 81.1% of lesions. Stable radiographic response was achieved in 86.7% of lesions with progression in 13%. Distant progression was observed overall in 75% of patients and average survival was 52.4 months. Conclusions: Malignant PCC and PGL often do not respond well to current systemic therapies. In these cases, EBRT can be considered in patients with symptomatic, localized disease progression.