title: Rectal separation using hydroxypropyl methylcellulose in intracavitary brachytherapy of cervical cancer: an innovative approach.
abstract: OBJECTIVE
  This study was initiated to prove feasibility of hydrogel application in recto-vaginal space in intracavitary brachytherapy (ICBT) of cervical cancer in order to reduce rectal toxicity.
  
  
  METHODS
  In a case of stage IIB cervical cancer, after external beam radiotherapy (EBRT), we planned ICBT 7 Gy × 3 fractions. In 1stfraction (Plan 1), due to narrow separation between rectum and cervix (0.18 cm), only 5 Gy was delivered at point A (with high-risk clinical target volume [HR-CTV] D905.94 Gy, intermediate risk clinical target volume [IR-CTV] D904.54 Gy, rectum D2cc5.72 Gy, bladder D2cc5.52 Gy, and sigmoid colon 5.82 Gy). In 2ndfraction (Plan 2), interstitial brachytherapy (ISBT) was attempted. For the prescription of 5 Gy, we get dose levels almost similar to the 1stinsertion: HR-CTV D90(6.7 Gy), IR-CTV D90(3.06 Gy), bladder D2cc(5.7 Gy), rectum D2cc(4.8 Gy), sigmoid colon D2cc(1.3 Gy) (separation = 0.23 cm). During 3rdfraction (Plan 3), prior doing interstitial insertion, we instilled 50 cc of hydroxypropyl methylcellulose (Viscomet®) up to the tip of recto-vaginal septum. A repeat computed tomography (CT) scan was done 4 hours after Plan 3 treatment and it was re-planned (Plan 4) to find out migration of hydrogel if any and its dosimetric impact.
  
  
  RESULTS
  9 Gy was delivered to point A with a separation of 1.1 cm in Plan 3 (with HR-CTV D9016.4 Gy, IR-CTV D9011.3 Gy, rectum D2cc3.6 Gy, bladder D2cc6.9 Gy, and sigmoid colon 2.2 Gy). We achieved an optimum cumulative EQD2dose (HR-CTV D9098.4 Gy, IR-CTV D9076.1 Gy, rectum D2cc67.7 Gy, bladder D2cc73.2 Gy, and sigmoid colon 59.3 Gy). Hydrogel volume was decreased in Plan 4 without a major dosimetric changes.
  
  
  CONCLUSIONS
  Hydrogel instillation is a useful tool for recto-vaginal separation during cervical cancer brachytherapy. It increases therapeutic ratio without any adverse event.
authors.affiliation: Department of Radiotherapy, Medical Cancer Hospital, Siliguri, Darjeeling.
authors.forename: Swapnendu
authors.initials: S
authors.lastname: Basu
authors.affiliation: R.M.O. cum Clinical Tutor, Department of Radiotherapy, R.G. Kar Medical College & Hospitals, Kolkata.
authors.forename: Kazi Sazzad
authors.initials: KS
authors.lastname: Manir
authors.affiliation: Department of Radiotherapy, R.G. Kar Medical College & Hospitals, Kolkata, India.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Basu
authors.affiliation: Department of Radiotherapy, R.G. Kar Medical College & Hospitals, Kolkata, India.
authors.forename: Koushik
authors.initials: K
authors.lastname: Ghosh
keywords: brachytherapy; cervical cancer; rectal toxicity