Reporting of dose-volume specifications for "Martinez Universal Perineal Interstitial Template-based interstitial high-dose-rate brachytherapy for gynecological cancers" according to International Commission on Radiation Units and Measurements 58 with early clinical outcomes

Characteristics of preplan-based three-dimensional individual template-guided brachytherapy compared to freehand implantation

Image-guided adaptive intracavitary/interstitial brachytherapy (IC/IS IGABT) has exhibited superior dosimetry advantage and local control for locally advanced cervical cancer (LACC). Our group designed a type of cylindrical three-dimensional (3D) printed vaginal template combining an intracavitary applicator with straight and oblique interstitial needles according to the preplan on computed tomography images. This work aimed to research the consistency of the preplan with the treatment plan at every fraction to verify the practical guiding significance of the preplan. We also investigated the difference between 3D-printed template-guided implantation compared with freehand implantation for LACC. Twenty-six patients were treated with 3D-printed individual templates (3D template group), and 20 patients were treated by using freehand insertion (freehand group). Patients in the 3D template group would take a preplan one week before treatment to design and print the individual template, while the freehand group did not. All patients accepted volumetric rotational intensity-modulated radiotherapy at a dose of 49.4 Gy in 26 fractions and subsequent brachytherapy at a dose of 26 Gy in four fractions. All analyses were performed by utilizing SPSS 26. The insertion depth was decreased in fractions 1 and 4 compared with the preplan. None of the dose volume histogram parameters of fractions 1-3, nor the D_2cc of bladder and bowel at fraction 4 were barely changed compared with the preplan. The D₉₀ and D₉₈ of the high-risk clinical target volume in the 3D template group were statistically higher than those in the freehand group (p < 0.01). The D_2cc of the rectum, bladder, bowel, and sigmoid in the 3D template group were all lower than those in the freehand group (p < 0.01). The preplan in this research is consistent with treatment plans, which is important to ensure the feasibility of applying a 3D-printed template in brachytherapy. The 3D-printed individual guidance template was an effective method in brachytherapy for locally advanced cervical cancer.