Rakesh Kapoor1, Divya Khosla2, Arvind K Shukla1, Ritesh Kumar1, Rajesh Gupta3, Arun S Oinam1, Suresh C Sharma1. 1. Department of Radiotherapy and Oncology, Regional Cancer Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India. 2. 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. 3. Department of Surgery, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
Abstract
PURPOSE: To evaluate dosimetric and clinical outcome in patients of anal cancer treated with image-based interstitial high-dose-rate brachytherapy following chemoradiation. METHODS AND MATERIALS: 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.
PURPOSE: To evaluate dosimetric and clinical outcome in patients of anal cancer treated with image-based interstitial high-dose-rate brachytherapy following chemoradiation. METHODS AND MATERIALS: 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.