Feasibility and Outcome of Helical Tomotherapy for Irradiation in Pediatric Patients with Pineoblastoma

Abstract

Purpose/Objective: Pineoblastoma is an extremely rare primary tumor occurring in the pineal gland and belongs to the supratentorial primitive neuroectodermal tumors. Intensive multimodality treatment that combines surgery, craniospinal irradiation (CSI), and chemotherapy is needed for this uncommon disease. The purpose of this analysis was to assess the feasibility and outcome of helical tomotherapy (HT) for irradiation in pediatric patients with pineoblastoma. Materials and Methods: Between 07/07 and 06/11, three female pediatric patients with diagnosis of non-metastasic pineoblastoma were treated with HT in our institution. Patient's ages were 2, 12, and 13 years old, respectively. The two older patients were treated according to the InternationalSociety of Paediatric Oncology protocol which includes postoperative chemotherapy; then concurrent radiochemotherapy with vincristine weekly and maintenance chemotherapy. The younger patient received the Head Start II protocol which includes postoperative chemotherapy; then, autologous bone marrow transplantation followed by radiation therapy (RT). All received CSI with a total dose of 23.4 Gy at 1.8Gy/fraction. Additionally, the primary tumor site was boosted up to of 54-55.8 Gy. Acute toxicities were scored according to the Common Toxicity Criteria for Adverse Events version 4.0. Results: RT was completed without any interruption. The two older patients were evaluated as complete response (CR) after RT and the remaining younger patient as stable disease. No patient experienced local or distant recurrence. One patient with CR is alive with no evidence of disease after 57 months from diagnosis. The other one died after 47 months from diagnosis due to cerebral hemorrhage of unknown etiology. Finally, the younger patient is alive after 2months from diagnosis. Grade 3 hematologic toxicity and grade fatigue was experienced in all patients. In addition, grade 2 nausea and vomiting was observed in 2 patients. No other acute toxicity was reported. (Table presented). Mean conformity indexand mean homogeneity index was 0.82 and 1.07, respectively, for the tumor bed and 0.74 and 1.11, respectively, for the craniospinal axis. The averagedose received by the critical organs were: 39.05Gy to the brainstem, 5.47Gy on the crystalline lens, 12.54Gy to each eye, 24Gy to each nerve optic, 10,46Gy to the thyroid gland, 7.16Gy to each lung, 6.17Gy to the heart, 2.12Gy to each mammary gland, 6.65 to the liver, and 9.51Gy to each kidney. Conclusions: HT offers a safe and effective therapeutic option in the multidisciplinary management of pediatric patients with pineoblastoma. Acceptable conformity and homogeneity indexes were achieved. HT seems to have dosimetrical advantages over conventional RT which may potentially allow increasing the dose in the tumor bed while sparing surrounding normal tissues in order to achieve better outcome for this aggressive disease.