Clinical application of SIOPE guidelines in target definition for craniospinal irradiation in children / 中华放射肿瘤学杂志

ABSTRACT

Objective:According to the SIOPE (2018) guidelines, the whole brain target of patients undergoing craniospinal irradiation was delineated and the underdose of sub-structures which were not delineated in original plan was verified, aiming to provide evidence for the risk of whole brain recurrence of craniospinal irradiation and accumulate experience for the clinical application of SIOPE guidelines.Methods:Twelve children who underwent craniospinal irradiation were selected. As per the SIOPE guidelines in 2018, the CTV sub (including the superior orbital fissure, foramen rotundum, foramen ovale, jugular foramen, hypoglossal canal, internal auditory meatus and optic nerve) were delineated based on the original CTV old (whole brain plus sieve plate) to form PTV new. A rough PTV (PTV rough) was formed by giving a margin of 15 mm forward-downward (skull base) and 3 mm in the other directions. CRT old and IMRT old plans were designed based on PTV old. CRT new and IMRT new plans were designed based on PTV new. CRT rough plan was designed based on PTV rough. The omission of sub-structures based on CTV old and the underdose of CTV sub in each plan were evaluated. Results:A total of 78.6% of superior orbital fissure, 71.99% of foramen rotundum, 96.76% of foramen ovale, 88.5% of jugular foramen, 97.71% of hypoglossal canal, 99.48% of internal auditory meatus and 100% of optic nerve volume were missed based on CTV old. The target dose coverage of CTV sub based on CRT old and IMRT old was only 91.70% and 89.83%, respectively. The underdose was observed in 16.66%, 3.57%, 20.83%, 1.78% and 1.19% of sub-structures in CRT old, CRT new, IMRT old, IMRT new and CRT rough plans, respectively. Of the underdose of all sub-structures, 38.36% and 46.58% occurred in CRT old and IMRT old plans, respectively. Among them, the least and the most significant underdose occurred in foramen rotundum (0%) and foramen ovale (36.66%), respectively. Conclusions:As per the SIOPE guidelines, traditional brain tissue delineation (including sieve plate) is likely to omit part of the target during the cranial target definition of craniospinal irradiation. The most significant underdose occurs in foramen ovale, and more obvious in the IMRT plan. The plan based on the delineation of sub-structures can significantly improve the underdose. When AP-PA irradiation is adopted, a rough PTV is recommended to obtain approximate target dose coverage and organ of risk sparing, whereas it requires further clinical verification.