title: Can combined intracavitary/interstitial approach be an alternative to interstitial brachytherapy with the Martinez Universal Perineal Interstitial Template (MUPIT) in computed tomography-guided adaptive brachytherapy for bulky and/or irregularly shaped gynecological tumors?
abstract: BACKGROUND
  Interstitial brachytherapy (ISBT) is an optional treatment for locally advanced gynecological tumours for which conventional intracavitary brachytherapy (ICBT) would result in suboptimal dose coverage. However, ISBT with Martinez Universal Perineal Interstitial Template (MUPIT), in which ~10-20 needles are usually applied, is more time-consuming and labor-intensive than ICBT alone, making it a burden on both practitioners and patients. Therefore, here we investigated the applicability of a combined intracavitary/interstitial (IC/IS) approach in image-guided adaptive brachytherapy for bulky and/or irregularly shaped gynecological tumours for which interstitial brachytherapy (ISBT) was performed.
  
  
  METHODS
  Twenty-one consecutive patients with gynecological malignancies treated with computed tomography-guided ISBT using MUPIT were analyzed as cases for this dosimetric study. For each patient, the IC/IS plan using a tandem and 1 or 2 interstitial needles, which was modeled after the combined IC/IS approach, was generated and compared with the IS plan based on the clinical ISBT plan, while the IC plan using only the tandem was applied as a simplified control. Maximal dose was prescribed to the high-risk clinical target volume (HR-CTV) while keeping the dose constraints of D2cc bladder < 7.0 Gy and D2cc rectum < 6.0 Gy. The plan with D90 HR-CTV exceeding 6.0 Gy was considered acceptable.
  
  
  RESULTS
  The average D90 HR-CTV was 77%, 118% and 140% in the IC, IC/IS and IS plans, respectively, where 6 Gy corresponds to 100%. The average of the ratio of D90 HR-CTV to D2cc rectum (gain factor (GF) rectum) in the IC, IC/IS and IS plans was 0.8, 1.3 and 1.5 respectively, while GFbladder was 0.9, 1.4 and 1.6, respectively. In the IC/IS plan, D90 HR-CTV, GFrectum and GFbladder exceeded 100%, 1.0 and 1.0, respectively, in all patients.
  
  
  CONCLUSIONS
  These data demonstrated that the combined IC/IS approach could be a viable alternative to ISBT for gynecological malignancies with bulky and/or irregularly shaped tumours.
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22, Showa-machi, Maebashi, Gunma, 371-8511, Japan. oiketakahiro@gmail.com.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Oike
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22, Showa-machi, Maebashi, Gunma, 371-8511, Japan. tohno@gunma-u.ac.jp.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ohno
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22, Showa-machi, Maebashi, Gunma, 371-8511, Japan. snoda@gunma-u.ac.jp.
authors.forename: Shin-Ei
authors.initials: SE
authors.lastname: Noda
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22, Showa-machi, Maebashi, Gunma, 371-8511, Japan. h_kiyohr@gunma-u.ac.jp.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kiyohara
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22, Showa-machi, Maebashi, Gunma, 371-8511, Japan. k-ando@showa.gunma-u.ac.jp.
authors.forename: Ken
authors.initials: K
authors.lastname: Ando
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22, Showa-machi, Maebashi, Gunma, 371-8511, Japan. k-shibu@med.gunma-u.ac.jp.
authors.forename: Kei
authors.initials: K
authors.lastname: Shibuya
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22, Showa-machi, Maebashi, Gunma, 371-8511, Japan. tamakit@gunma-u.ac.jp.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Tamaki
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22, Showa-machi, Maebashi, Gunma, 371-8511, Japan. t_kusagi@yahoo.co.jp.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Takakusagi
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22, Showa-machi, Maebashi, Gunma, 371-8511, Japan. h-sato0808@hotmail.co.jp.
authors.forename: Hiro
authors.initials: H
authors.lastname: Sato
authors.affiliation: Department of Radiation Oncology, Gunma University Graduate School of Medicine, 3-39-22, Showa-machi, Maebashi, Gunma, 371-8511, Japan. tnakano@med.gunma-u.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakano
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D005833:Genital Neoplasms, Female / Q000000981:diagnostic imaging / Q000473:pathology* / Q000532:radiotherapy*; D006801:Humans; D009367:Neoplasm Staging; D058958:Organs at Risk / Q000528:radiation effects; D011379:Prognosis; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden