Application of 3D Printed Multi-Channel Vaginal Cylinder for Vaginal Brachytherapy in the Cervical Cancer Invading the Middle and Lower Thirds of Vagina

Abstract

<h3>Purpose/Objective(s)</h3> Patients with cervical cancer invading the middle and lower thirds of vagina (CCIV) had high recurrence rates and worse prognosis. Single-channel vaginal cylinder (SCVC) could make the dose curve wrap completely around the high-risk clinical target volume (HRCTV) for CCIV patients. However, the dose of HRCTV and organs at risk (OARs) would increase at the same time for symmetrical dose distribution of SCVC dose curve, especially in patients with eccentric distribution of the tumor. It was still difficult to achieve a conformal target dose distribution when the SCVC's lead block was used for protecting the OARs. The 3D printed multi-channel vaginal cylinder (3D-MCVC) could arrange the radioactive source according to the tumor location. But there was very little foundation in the literature on dose contrasting in SCVC and MCVC for brachytherapy in CCIV. Therefore, this study proposed to confirm that 3D-MCVC brachytherapy (3D-MCVCB) was better than SCVCB to reduce the OARs dose and achieved conformal target dose distribution. <h3>Materials/Methods</h3> All patients were given the dose of 28Gy/4fraction/4week for brachytherapy. According to ICRU89 document, HRCTV and OARs (the bladder, rectum, and sigmoid colon) were contoured on the CT images in the Nuclear 3D brachytherapy radiotherapy treatment planning system. By self-control study, a simulation plan for the SCVCB was matched while making a 3D-MCVCB plan. The two plans of OARs doses (D_2cc, D_1cc, D_0.1cc) and HRCTVD₉₀ were divided into 3D-MCVCB groups and virtual SCVCB groups, separately. The statistical analysis was the paired sample t-test. <h3>Results</h3> From October 2018 to May 2021, 16 patients of CCIV were included. 128 plans were made for two groups. The prescription dose for HRCTV was 7Gy/1f. When HRCTVD₉₀ was almost 7Gy in the virtual SCVCB group, the doses of OARs were roughly at the threshold of dose limiting. However, when HRCTVD₉₀ of 3D-MCVC group was 7.45±0.47Gy, all OARs doses of 3D-MCVCB group were lower than them of SCVCB group, (P<0.05) (Table1). <h3>Conclusion</h3> The empirical findings in this study provided a new understanding that 3D-MCVCB achieved more conformal target dose distribution for CCIV patient. 3D-MCVCB could better maximize the dose to target tissues and minimize the dose to organs at risk (OARs) than SCVCB. Furthermore, the clinical efficacy and adverse reactions need to be further studied. Table 1. Doses given for HRCTVD₉₀ and OARs for the whole group of plans (n = 128)