Interstitial brachytherapy vs. intensity-modulated radiation therapy for patients with cervical carcinoma not suitable for intracavitary radiation therapy

Abstract Purpose Interstitial brachytherapy (IBT) is the standard alternative treatment for patients with cervical carcinoma not suitable for intracavitary radiotherapy. There is an emerging belief that intensity-modulated radiotherapy (IMRT) has the potential to replace IBT. We aimed to compare the dosimetry achieved by IBT and IMRT in such patients. Methods and Materials The CT imaging data, previously used for IBT planning of 12 patients with cervical carcinoma, were transferred to IMRT planning system to generate parallel IMRT plans. Prescribed dose to the planning target volume (PTV) was 20 Gy delivered in 2-weekly high-dose-rate fractions of 10 Gy each with IBT (biologically equivalent dose [BED 10 ] 40 Gy) and 33 Gy/13 fractions/2.5 wk with IMRT (BED 10 41 Gy). For comparison, dose–volume parameters for target and organs at risk were recorded and expressed in terms of BED 10 and BED 3 , respectively. Results For PTV, the mean D 95 (dose received by 95% of PTV) was better with IBT (57.16 Gy vs. 41.47 Gy, p  = 0.003). The mean conformity index was 0.94 and 0.90 with IBT and IMRT, respectively ( p  = 0.034). IBT delivered significantly reduced doses to 1.0 cc ( D max ), 5.0 cc ( D 5 cc ), 50% ( D 50 ), and 75% ( D 75 ) of bladder volume as compared with IMRT. The mean rectal D max was significantly better with IBT as compared with IMRT (54.64 Gy vs. 62.63 Gy, p  = 0.02). Conclusions IBT provides superior PTV coverage and organs at risk sparing to IMRT. Thus, IBT remains the standard treatment for patients with cervical carcinoma unsuitable for intracavitary radiotherapy.