Page 145 - Organ motion in children for high-precision radiotherapy - Sophie Huijskens

treated without (> 8 years) [9]. Although GA will assure patient immobilization during treatment delivery, it seems that the influence of GA on respiratory-induced motion is inconsistent, assuming that breathing remains patient-specific. Since it also requires adequate consumption restrictions, increases health risks, is labor intensive, increases preparation and treatment time, and could have negative effects after treatment [52, 53], the use of GA on a daily basis for prolonged periods is not preferred and other options should be considered. Play preparation by a specialized radiation therapist can increase comfort and familiarity with radiation treatment in order to minimize or even eliminate the use of sedatives and GA [47, 49, 54]. Additionally, children can benefit from having audiovisual interventions as a distraction from the treatment delivery, and this can also reduce the need of daily anesthesia for radiotherapy in children [55, 56]. However, the direct impact of these video or musical interventions on interfractional position variation or respiratory motion has not been studied so far.
Breath holding
In the second part of this thesis we showed large variation in respiratory-induced diaphragm motion in children. Others found substantial motion of surrounding OARs in the three orthogonal directions [1, 8–10]. In adults, respiratory motion management systems have been introduced to control or reduce the respiratory-induced motion of organs and tumors in the upper-abdomen and thoracic area [57]. Breath-holding techniques are feasible and widely used in adult patients, achieving a more stable tumor position and thereby improving treatment delivery [58]. However, it is of concern that tumors do not stay completely still during breath holding. During inhalation breath-holding, the lung volume gradually decreases because oxygen is extracted from alveolar gas [59]. This leads to motion of the diaphragm [59–61], and possibly contributes to drifting of the tumor as well [62]. Nevertheless, inhalation breath-holding is widely used in adult radiotherapy. In particular for breast radiotherapy, in order to minimize high doses to the heart without compromising target coverage [63]. For a similar purpose in pediatric patients with Hodgkin’s disease with mediastinal involvement, Claude et al. showed that with an active breathing control (ABC) device children older than 13 years were capable of holding their breath for 15-20 s without any problem, stress or discomfort [64]. Lung and heart dose was decreased using ABC, while for other OARs no significant change was found. Since the procedure of ABC required two to three times more time for explanation and training, the benefit of dose reduction should be well balanced with increasing time and thereby costs [64]. Demoor et al. showed that children (age range 9-20 years) with a deep inspiration breath hold (DIBH) technique were able to hold their breath for 10-18 seconds [65]. However, although children treated with DIBH showed a significantly sparing of normal liver tissue compared to children treated under free breathing, no differences in toxicity between the two groups were found. To further establish the clinical long-term benefit, a prospective study is needed. In particular to know how much reduction of irradiated volume of the OARs, and more precisely in which parts of the OARs, leads to clinical benefits. Therefore, recently, Lundgaard et al. introduced a study protocol TEDDI (radiotherapy delivery in deep-inspiration) to assess the potential benefit of DIBH in children [66].
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