Pediatric Craniospinal Irradiation – The implementation and Use of Normal Tissue Complication Probability in Comparing Photon versus Proton Planning

Abstract

Purpose: The preferred radiotherapy treatment for medulloblastoma is craniospinal irradiation (CSI). With the aim of developing the potential to reduce normal tissue dose and associated post-treatment complications with photon and proton radiotherapy techniques for CSI. This report aims to carefully compare and rank treatment planning and dosimetric outcomes for pediatric medulloblastoma patients using normal tissue complication probability (NTCP) formalism between photon (three-dimensional conformal radiotherapy, intensity-modulated radiotherapy [IMRT], volumetric-modulated arc therapy [VMAT], and HT) and proton CSI. Methods and Materials: The treatment data of eight pediatric patients who typically received CSI treatment were used in this study. The patients were 7 years of age on average, with ages ranging from 3 to 11 years. A prescription dose of 3600 cGy was delivered in 20 fractions by the established planning methods. The Niemierko's and Lyman–Kutcher–Burman models were followed to carefully estimate NTCP and compare different treatment plans. Results: The NTCP of VMAT plans in upper and middle thoracic volumes was relatively high compared to helical tomotherapy (HT) and pencil beam scanning (PBS) (all P < 0.05). PBS rather than IMRT and VMAT in the middle thoracic region ( P < 0.06) could significantly reduce the NTCP of the heart. PBS significantly reduced NTCP of the lungs and liver (all P < 0.05). Conclusion: The NTCP and tumor control probability (TCP) model-based plan ranking along with dosimetric indices will help the clinical practitioner or medical physicists to choose the best treatment plan for each patient based on their anatomical or clinical challenges.

Comparison of Craniospinal Irradiation Using Proton Beams According to Irradiation Method and Initial Experience Treating Pediatric Patients

“…They concluded that the doses to the lens, thyroid gland, lungs, heart, spleen, kidneys, esophagus, and optic nerve were significantly lower in the IMPT group. 19 In our study, the maximum dose to the lens exceeded 10 Gy (RBE), which created dose constraints in our hospital in 4 out of the 8 patients in the PSPT group because of the need to ensure a sufficient dose to the cribriform plate. In contrast, the maximum dose did not exceed the threshold in any of the 16 patients in the IMPT group.…”

“…Giantsoudi et al 18 investigated a simulation study and revealed that the dose conformity of IMPT was better than that of PSPT, and a significant dose decrease was observed in the esophagus. In a similar study, Balasubramanian and Shobana 19 conducted a comparative study of IMPT, intensity modulated RT, helical tomotherapy, and volumetric-modulated arc therapy in 8 patients. They concluded that the doses to the lens, thyroid gland, lungs, heart, spleen, kidneys, esophagus, and optic nerve were significantly lower in the IMPT group.…”

“… 15 , 16 The number of facilities offering IMPT is growing rapidly worldwide. IMPT is expected to be advantageous for the treatment of CSI because of the normal tissue dose reduction and target dose robustness, but its actual effectiveness has only been discussed in a few papers describing a very small number of patients (less than 10) 17 , 18 , 19 because of the small number of patients requiring CSI at most proton beam facilities and the few facilities that can perform this therapy. On a technical note, the vertebral body sparing (VBS) technique is recommended to avoid hematologic toxic effects.…”

Dosimetric and radiobiological comparison of IMRT, VMAT, and helical tomotherapy planning techniques in hippocampal sparing whole brain radiotherapy with simultaneous integrated boost for multiple brain metastases

“…We have studied the possibility of sparing the hippocampus and other OARs while performing the WBRT and simultaneous boost with the three planning methods and compare these plans with dosimetric, EUD, and radiobiological models. Balasubramanian et al [22,23] compared photon and proton planning radiobiologically using LKB and Niemierko NTCP models, and they found that the results were reliable for comparing different planning methods.…”

Comparison of Acute Hematological Adverse Reactions Induced by Craniospinal Irradiation With Intensity-Modulated Radiotherapy and Conventional Radiotherapy

“…These new radiotherapy techniques produce significant improvements in dose distribution in the target volume and the junction layer. 3 , 4 However, they also expand the low dose range of irradiation, which may generate severe myelosuppression when the prescribed dose is consistent with that of CSI-CRT. 5 Severe myelosuppression in patients often affects the smooth progress of CSI treatment 6 and also reduces the tumor cure rate, 7 so it has become a hot issue of concern to clinicians.…”