Patient 1

Patient 1 was a 56 year-old woman with stage IA serous endometrial cancer who was referred for vaginal cuff brachytherapy following chemotherapy. Based on physical examination, the optimal applicator size was determined to be a 2.75 cm diameter vaginal cylinder. Because vaginal cylinder applicators at our institution are available only in 2.5, 3, or 3.5 cm diameter sizes, we decided to produce a custom-sized applicator using three-dimensional printing technology to better fit this patient's anatomy. This simple case also served as a proof of concept for the initial clinical implementation of a 3D printed custom vaginal applicator in our clinic. We used CAD software (Autodesk, Inc., San Francisco, CA, USA) to design a 2.75 cm diameter segmented cylinder with a single central channel. The cylinder was printed on a Fortus 400mc (Stratasys Ltd., Eden Prairie, MN, USA) three-dimensional printer, using PC-ISO biocompatible thermoplastic (Figure 1). The thermoplastic cylinder was sterilized using a STERRAD (Ethicon, Inc., Sommerville, NJ, USA) sterilization system.

Picture of the custom printed segmented cylinder sections with 2.75 cm diameter. The segments are stacked onto a plastic rod with a central channel for treatment as shown

At the time of treatment, two gold seed fiducial markers were inserted into the vaginal cuff prior to the first insertion. The sterilized cylinder was placed in the vagina, secured with a metal applicator clamp and baseplate, and the position was verified on scout film. Computed tomography images of the treatment area were obtained, and the applicator and organs at risk were contoured on Elekta Nucletron Oncentra Planning System (Verson 4.3; Elekta Instrument AB, Stockholm, Sweden). Three-dimensional inverse planning using inverse planning simulated annealing algorithm (IPSA) was used to develop a treatment plan to deliver 31.5 Gy over three fractions of 10.5 Gy per fraction, prescribed to the surface of the vagina. The applicator surface was used as a proxy for vaginal surface for the purposes of treatment planning. The IPSA class solution was designed with the goal of achieving 10.5 Gy to the surface of vagina. The length of vagina treated was based on physician's contour, which included the upper two-thirds of the vaginal canal. Coverage was verified by visual confirmation of the confluence of the 10.5 Gy isodose surface with the applicator surface. 3D volumetric doses were calculated for the bladder, rectum, bowel, and the target volume. The treatment was delivered using Elekta Nucletron microSelectron V3 remote afterloader (Elekta Instrument AB, Stockholm, Sweden).