title: Interfractional change of high-risk CTV D90 during image-guided brachytherapy for uterine cervical cancer.
abstract: The purpose of this study was to evaluate interfractional changes of the minimum dose delivered to 90% of the high-risk clinical target volume (HR-CTV D90) and D2cc of the bladder and rectum during brachytherapy for uterine cervical cancer patients. A total of 52 patients received external beam radiotherapy and high-dose-rate intracavitary brachytherapy (ICBT). For each of four ICBT applications, a pelvic CT scan was performed and the HR-CTV was delineated. Retrospectively, these patients were divided into two groups: (i) the standard dose group with 6 Gy to point A in each ICBT, and (ii) the adaptive dose group with a modified dose to point A to cover the HR-CTV with the 6-Gy isodose line as much as possible. The HR-CTV D90 was assessed in every session, and analyzed as interfractional changes. In the standard dose group, the interfractional changes of the HR-CTV D90 showed a linear increase from the first to the third of the four ICBT (average 6.1, 6.6, 7.0 and 7.1 Gy, respectively). In contrast, those of the adaptive dose group remained almost constant (average 7.2, 7.2, 7.3 and 7.4 Gy, respectively). Especially, in the case of a large HR-CTV volume (≥35 cm(3)) at first ICBT, the total HR-CTV D90 of the adaptive dose group with brachytherapy was significantly higher than that of the standard dose group. There were no significant differences in total D2cc in bladder and rectum between the two groups. Image-guided adaptive brachytherapy based on interfractional tumor volume change improves the dose to the HR-CTV while keeping rectal and bladder doses within acceptable levels.
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, 371-8511, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Ohkubo
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ohno
authors.forename: Shin-ei
authors.initials: SE
authors.lastname: Noda
authors.forename: Nobuteru
authors.initials: N
authors.lastname: Kubo
authors.forename: Akiko
authors.initials: A
authors.lastname: Nakagawa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kawahara
authors.forename: Takanori
authors.initials: T
authors.lastname: Abe
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kiyohara
authors.forename: Masaru
authors.initials: M
authors.lastname: Wakatsuki
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakano
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001822:Body Burden; D001918:Brachytherapy / Q000379:methods*; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects; D011835:Radiation Protection / Q000379:methods*; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D012007:Rectum / Q000528:radiation effects*; D016896:Treatment Outcome; D001743:Urinary Bladder / Q000528:radiation effects*; D014594:Uterine Neoplasms / Q000175:diagnosis / Q000532:radiotherapy*
keywords: 3D image-based planning; dose-volume histogram analysis; high-dose-rate brachytherapy; radiotherapy; uterine cervical cancer