Craniospinal Irradiation Using Helical Tomotherapy: Evaluation of Acute Toxicity and Dose Distribution

Abstract

The purpose of this study was to evaluate acute toxicity of craniospinal irradiation (CSI) using helical tomotherapy (HT) and compare its dose distribution with that of conventional linac-based plans. Twelve patients with various brain tumors were treated with HT-CSI. Median patient age was 14 years (range: 4-37 years). Median CSI dose was 30.6 Gy in 18 fractions (range: 23.4-40 Gy in 13-25 fractions). Toxicities were assessed according to the Common Terminology Criteria for Adverse Events version 4.0. Before CSI, 11 patients (92%) received neoadjuvant chemotherapy, so acute toxicity was evaluated by comparing patient status before and after CSI. HT-CSI plans were compared with linac-based CSI plans made using Pinnacle 3 planning system in 9 patients. All patients completed planned CSI without interruption. Grade 3 or higher toxicities were leukopenia seen in 11 patients (92%), anorexia in 6 (50%), anemia in 5 (42%), and thrombopenia in 5 (42%). Administration of granulocyte colony-stimulating factor, platelet transfusion and total parenteral nutrition were required in 8 (67%), 5 (42%) and 5 (42%) patients, respectively. HT plans were superior to linac-based plans in terms of homogeneity and conformality in planning target volume (PTV). For most organs at risk (OARs), volumes receiving more than 10 Gy (V10 Gy) or 20 Gy (V20 Gy) were lower in HT plans. However, HT plans significantly increased mean doses to the lung, kidneys and liver, and V5 Gy of 6 OARs including the lung. Despite intensive neoadjuvant chemotherapy, acute toxicity of HT-CSI was acceptable. HT provided better dose distribution in PTV than conventional linac. In most OARs, smaller volumes received >10-20 Gy in HT plans, although larger volumes received 5-10 Gy.

Craniospinal irradiation using helical tomotherapy for central nervous system tumors

“…HT-CSI is superior from this perspective because it allows planning of the entire neuroaxis as one field. Moreover, conformity of dose distribution to the target volume has been shown to be higher for HT than for 3DCRT [8, 20, 23–25]. This can be confirmed by our HT plans.…”

Assessment of Three-dimensional Set-up Errors using Megavoltage Computed Tomography (MVCT) during Image-guided Intensity-modulated Radiation Therapy (IMRT) for Craniospinal Irradiation (CSI) on Helical Tomotherapy (HT)

“…This unique feature of HT has been explored for CSI with promising dosimetric and early clinical results (11)(12)(13)(14). However, despite rapid adoption of newer technology in clinical practice, there is a paucity of data on set-up errors during CSI and the appropriate margins required thereof for ensuring adequacy of target volume coverage.…”

Haematological toxicity in adult patients receiving craniospinal irradiation – Indication of a dose-bath effect

“…This technique results in field junctions where the delivered absorbed dose is very uncertain [2], an inhomogeneous dose distribution in the planning target volume (PTV), and a high absorbed dose to some organs at risk (OARs), e.g. the thyroid gland, heart, and sternum [3]. The unique geometry of helical tomotherapy (HT) enables the possibility of treating the entire craniospinal axis without any field junctions or field matching [4].…”

“…This so-called dose bath may be associated with acute and late adverse effects, e.g. haematological toxicity and secondary cancers [3,5,[7][8][9][10][11][12]. Thus, even if a HT plan can fulfil typical normal tissue tolerance criteria better than a 3DCRT plan, it does not necessarily mean that the therapeutic result is better as a different spectrum of side-effects might become apparent.…”