title: Dosimetric and clinical outcome in image-based high-dose-rate interstitial brachytherapy for anal cancer.
abstract: OBJECTIVE
  To evaluate dosimetric and clinical outcome in patients of anal cancer treated with image-based interstitial high-dose-rate brachytherapy following chemoradiation.
  
  
  METHODS
  Sixteen patients with anal cancer were treated with chemoradiation followed by brachytherapy boost with image-based high-dose-rate interstitial brachytherapy from January 2007 to June 2011. Two brachytherapy dose schedules were used: 21 Gy in seven fractions and 18 Gy in six fractions depending on response to chemoradiation. CT scan was done after placement of needles for confirmation of placement and treatment planning. Target volume was contoured on CT scans. Volumetric quality indices and dose parameters were calculated.
  
  
  RESULTS
  The mean clinical target volume was 17.7 ± 4.98 cm(3), and the median overall tumor size was 4.2cm (3.4-5cm). The mean values of coverage index, dose homogeneity index, overdose volume index, dose non-uniformity ratio, and conformal index were 0.94, 0.83, 0.21, 0.37, and 0.88, respectively. With a median followup of 41 months (range, 20-67.2 months), preservation of the anal sphincter was achieved in 14 patients. The 1- and 2-year local control rates were 93.8% and 87.5%, respectively. Treatment was well tolerated and none of the patients developed Grade 3 or higher late toxicity.
  
  
  CONCLUSIONS
  The combination of external beam radiotherapy with interstitial brachytherapy increases the dose to the tumor volume and limits the volume of irradiated normal tissue, thereby decreasing late toxicity. The use of image-based treatment planning provides better dose conformality with reduced toxicity and helps to prevent a geographic miss.
authors.affiliation: Department of Radiotherapy and Oncology, Regional Cancer Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Rakesh
authors.initials: R
authors.lastname: Kapoor
authors.affiliation: Department of Radiotherapy and Oncology, Regional Cancer Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India. Electronic address: dr_divya_khosla@yahoo.com.
authors.forename: Divya
authors.initials: D
authors.lastname: Khosla
authors.affiliation: Department of Radiotherapy and Oncology, Regional Cancer Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Arvind K
authors.initials: AK
authors.lastname: Shukla
authors.affiliation: Department of Radiotherapy and Oncology, Regional Cancer Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Ritesh
authors.initials: R
authors.lastname: Kumar
authors.affiliation: Department of Surgery, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Gupta
authors.affiliation: Department of Radiotherapy and Oncology, Regional Cancer Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Arun S
authors.initials: AS
authors.lastname: Oinam
authors.affiliation: Department of Radiotherapy and Oncology, Regional Cancer Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Suresh C
authors.initials: SC
authors.lastname: Sharma
mesh_terms: D000328:Adult; D000368:Aged; D001005:Anus Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000532:radiotherapy*; D001918:Brachytherapy / Q000379:methods*; D059248:Chemoradiotherapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015641:Radiography, Interventional; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D018714:Radiotherapy, Adjuvant; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
keywords: Anal cancer; High dose rate; Image based; Interstitial brachytherapy; Quality indices