Dosimetry comparison between a 3D printed minimally invasive guidance template and free implantation in the brachytherapy treatment of postoperative recurrent cervical carcinoma

Objective: This study aimed to investigate the dosimetry difference between a 3D printed minimally invasive guidance template and conventional free implantation in brachytherapy of postoperative recurrent cervical carcinoma under the guidance of computed tomography (CT). Methods: A total of 21 cases of patients with recurrent cervical cancer after operation were enrolled from January 2017 to June 2018. After external irradiation treatment in 1.8-Gy fractions to 45 Gy, patients were randomly divided into two groups to receive brachytherapy: 11 cases were assisted by a 3D-printed minimally invasive guidance template, and the other 10 cases were free implantation. In the template group, needles were inserted according to the main guide channel of the template commissioned in medical photosensitive resin, while patients in the other group were treated with bare hands under the guidance of CT, which was used in both groups to adjust the position and depth of the implant needles. After transmission of the CT images into the Oncentra® Brachy TPS system, the target organs and organs at risk were delineated for further treatment. Results: The D(90) value of the high-risk clinical target volume in the template group was 6.30±0.21 Gy while that in the other group was 6.07±0.32 Gy (P<0.05). In addition, the D2cm(3 )(illuminated dose of 2 cm(3 )of organ at risk) value of the bladder, rectum, sigmoid colon, and bowel was significantly decreased in the template group as compared to the free group (P<0.05). The number of needles used for each treatment in the template group was 5.71±1.82, while that for the free injection group was 7.78±2.35 (P<0.05). Conclusion: Compared with conventional free implantation, the 3D printed minimally invasive guidance template-assisted treatment has an obvious dosimetry advantage in the treatment of postoperative recurrent cervical carcinoma, with shorter time of implantation and better repeatability.