Method for reducing radiation exposure to rectum during brachytherapy for patients with cervical cancer

Abstract

FIELD: radiation oncology; gynecology.SUBSTANCE: used in the treatment of cervical cancer. Magnetic resonance imaging of the pelvis is performed to assess residual cervical tumor. The projection point of the cervix is determined in the area of intersection of a conditional parallel line corresponding to the plane of the rectum and a perpendicular line to the plane of the cervix. The distance between the rectal wall and the vagina is measured at this point. The spacer dose is calculated taking into account the thickness of the fatty tissue between the rectum and the vaginal wall: if the thickness is 3 mm or less, 10 ml of spacer is inserted; if more than 3 mm, 5 ml of spacer is inserted.EFFECT: significant reduction in radiation exposure to the rectum, the elimination of the development of late radiation damage, and an improvement in the quality of life of patients with cervical cancer by taking into account the individual anatomical and physiological parameters of the patient.2 cl, 5 dwg, 1 tbl, 2 ex

Description

[0001] The invention relates to medicine, namely to radiation oncology, and concerns brachytherapy of patients with cervical cancer with the implantation of a spacer in the fatty tissue between the rectum and the vagina at the projection point of the cervix.

[0002] With the increasing life expectancy of cervical cancer patients, new medical and social problems associated with brachytherapy are becoming apparent. Late radiation injuries occur in 9% of patients; however, in 5% of cases, these are severe and potentially life-threatening conditions that negate treatment results, significantly reduce quality of life, and in some cases lead to disability and death [Tohidinezhad F., Willems Y., et al. Prediction models for brachytherapy-induced rectal toxicity in patients with locally advanced pelvic cancers: a systematic review / / J Contemp Brachytherapy. - 2022. - Vol. 14, No. 4. - P. 411-422. - DOI: 10.5114 / jcb.2022.119427]. Based on data from a large international prospective study, EMBRACE (international study of MRI-based BRAchytherapy for CErvical cancer) [https: / / www.embracestudy.dk, link found on the Internet, accessed 14.10.2025] it has been proven that the radiation dose to the rectal wall is D2cm. 3 (dose delivered to 2 cm 3 (rectum) less than 65 Gy is associated with a lower incidence of late radiation damage in the form of proctitis and rectal bleeding. At doses greater than 75 Gy, more severe damage is observed with the development of serious complications, such as rectovaginal fistulas. Thus, control of the radiation dose to the rectum within 65 Gy or less significantly reduces the risk of developing late radiation proctitis and associated complications, and exceeding 75 Gy is associated with a higher probability of severe consequences [Tanderup K., , et al. Risk factors for ureteral stricture after radiochemotherapy including image-guided adaptive brachytherapy in cervical cancer: results from the EMBRACE studies / / Int J Radiat Oncol Biol Phys. - 2019. - Vol. 103, No. 4. - P. 887-894. - DOI: 10.1016 / j.ijrobp.2018.11.006. - PMID: 30419309. - Epub 2018 Nov 10.]. Peng QH et al. in their study analyzed the treatment results and prognosis in patients with cervical cancer, demonstrating that the severity of radiation proctitis depends on the received dose of ionizing radiation, measured as D2cm 3to the rectal wall, amounted to 73.4 Gy on average. This value exceeded a similar indicator in patients without manifestations of radiation damage by 3.9 Gy. The results of the study emphasize the direct dependence of the degree of radiation damage on the magnitude of the dose effect on the rectal wall during brachytherapy. Therefore, optimization of treatment protocols in order to reduce the dose load on critical structures can significantly reduce the incidence and severity of late radiation injuries, such as radiation proctitis, and help maintain the quality of life of patients after radiation therapy [Peng QH, et al. Analysis of treatment outcomes and prognosis after concurrent chemoradiotherapy for locally advanced cervical cancer / / Front Oncol. - 2022. - Vol. 12. - Article 926840. - DOI: 10.3389 / fonc.2022.926840].

[0003] Biodegradable spacers have proven themselves in the treatment of prostate cancer as an effective means of significantly reducing the radiation load on the rectum [Novikov S.N., Novikov R.V., et al. Method for reducing the radiation load on the rectum in the treatment of prostate cancer: Russian Federation patent for invention No. 2805644 C1, application No. 2022129805 dated November 16, 2022, registered October 23, 2023. Available: https: / / www.elibrary.ru / item.asp?id=56006021]. Spacers create additional anatomical space, which reduces the radiation dose affecting the rectal tissues, and thereby reduces the risk of radiation damage [Fischer-Valuck BW, Chundury A., et al. Hydrogel spacer distribution within the perirectal space in patients undergoing radiotherapy for prostate cancer: Impact of spacer symmetry on rectal dose reduction and the clinical consequences of hydrogel infiltration into the rectal wall / / Pract Radiat Oncol. - 2017. - Vol. 7, No. 3. - P. 195-202. - DOI: 10.1016 / j.prro.2016.10.004.; Mariados NF, Orio PF et al. Hyaluronic acid spacer for hypofractionated prostate radiation therapy: a randomized clinical trial / / JAMA Oncol. - 2023. - Vol. 9, No. 4. - P. 511-518. DOI:10.1001 / jamaoncol.2022.7592]. In oncourology, a water-containing biopolymer with silver ions, for example, Bafflex, is used as a volume-forming agent (spacer) [Solodkiy V.A., Pavlov A.Yu., et al. Effect of polyacrylamide-based rectal gel spacers on dose distribution and rectal toxicity during high-intensity brachytherapy for prostate cancer / / Issues of oncology. - 2024. - V. 70, No. 2. - P. 299-307]. Sterile, highly viscous, homogeneous, gelatinous polymer, colorless or light yellow, odorless in a 5.0 ml disposable syringe [Instructions for use of the biodegradable spacer BUFFLEX / TU 32.50.50-001-52820385-2022. - 2022].Unlike urological oncology, where the use of spacers has found its application, it is not a standard practice in gynecological oncology due to the peculiarities of anatomy and treatment protocols. There are isolated reports on the possibility of using hydrogel in safely delivering whole pelvic radiation therapy without central shielding in computed tomography-based image-guided adaptive brachytherapy for uterine cervical cancer patients [Nagao A., Murakami N., et al. Role of the gel spacer in safely delivering whole pelvic radiation therapy without central shielding in computed tomography-based image-guided adaptive brachytherapy for uterine cervical cancer patients / / Brachytherapy. - 2024. - Vol. 23, No. 5. - P. 595-603. - DOI: 10.1016 / j.brachy.2024.05.007.; Damato AL, et al. Rectum and bladder spacing in cervical cancer brachytherapy using a novel injectable hydrogel compound / / Brachytherapy. - 2017. - Vol.16, No. 5. - P. 949-955. - DOI: 10.1016 / j. brachy.2017.04.236.- Epub Jun 12, 2017. - PMID: 28619385].

[0004] The technical result of the invention consists in using a spacer to reduce the radiation load during brachytherapy of cervical cancer patients while maintaining dosimetric parameters for the tumor.

[0005] This result is achieved by increasing the distance between the anterior rectal wall (1) and the posterior vaginal wall (2) to 10 mm or more. This is accomplished by inserting a spacer into the rectovaginal fat pad located between the rectal (1) and vaginal (2) walls, positioning the spencer needle at the projection point of the cervix (3) before brachytherapy begins.

[0006] The spacer dosage is determined based on the patient's anatomical and physiological parameters. If the thickness of the fatty tissue between the rectum and vaginal wall is 3 mm or less, a 10 ml spacer is inserted. If the thickness is greater than 3 mm, a 5 ml spacer is inserted.

[0007] This dosage is due to the need to ensure an optimal distance between the pelvic organs to reduce the radiation dose to the rectum during brachytherapy for maximum clinical effectiveness and safety of the procedure.

[0008] The claimed method is carried out as follows.

[0009] On the eve of the procedure, magnetic resonance imaging (MRI) of the pelvis is performed, residual tumor of the cervix is ​​assessed, the distance between the wall of the rectum (1) and the vagina (2) in the projection of the cervix (3) is measured.

[0010] The projection point of the cervix (3) is determined in the area of ​​intersection of the conditional parallel line corresponding to the plane of the rectum (1) and the perpendicular line - the plane of the cervix (3) (Fig. 1).

[0011] This method takes into account individual anatomical features and facilitates optimal placement of the spacer to effectively reduce radiation exposure to the rectum.

[0012] The procedure is performed under epidural anesthesia in order to reduce pain and increase patient comfort.

[0013] On the day of the examination, a cleansing enema is administered. The patient is then placed on a gynecological examination table, lying supine with her legs spread wide and slightly elevated, knees bent. A catheter is inserted, and the bladder is filled. An endorectal probe (5) is inserted into the rectum and secured to a stepper (6). The perineal skin is cleansed with an antiseptic solution.

[0014] Through the perineal skin under U3 control in the sagittal scanning plane, a guide needle (7) is introduced into the fatty tissue between the rectum (1) and the vagina (2) to the point of implantation of the spacer (4) (Fig. 2).

[0015] When the guide needle (7) reaches the planned insertion point (4), a spacer (8) is implanted to create a space between the anterior wall of the rectum and the posterior wall of the vagina. The needle is removed (Fig. 3).

[0016] An aseptic dressing is applied to the perineal skin. The patient is transferred to the ward for observation. The first brachytherapy session is performed the day after spacer implantation.

[0017] The method was tested in 17 clinical cases. It was found that by increasing the distance from the anterior rectal wall (1) to the cervix (3) to 10 mm or more, the radiation dose to the anterior rectal wall decreases by 30%-40% (Table 1).

[0018]

[0019] The method is illustrated by clinical examples.

[0020] Clinical example 1. Patient K., 35 years old. Clinical diagnosis: cervical cancer stage IIIC rT2bN1M0. PGI dated 04 / 09 / 2025: morphological picture of moderately differentiated adenocarcinoma of the cervix. Multidisciplinary oncology council dated 04 / 28 / 2025: chemoradiation therapy. From 05 / 05 / 2025 to 06 / 04 / 2025, conformal radiation therapy was performed on a linear accelerator using fixing devices and volumetric visualization of the target. Total dose (SD) = 46 Gy. Right external iliac lymph node boost (SD EQD2) - equivalent dose in 2 Gy fractions (bOGy) with weekly administration of Carboplatin, SD 937 mg. The next stage was brachytherapy. MRI topometry was performed using a ring applicator. Radiation target volume: GTV - visualized cervical tumor, HR - high-risk CTV - the entire cervix without safety margins, IR-intermediate-risk CTV - safety margins of 10 mm.

[0021] A preliminary calculation of the dosimetry plan before inserting the spacer was performed using the BrachyVision™ treatment planning system. The calculated data showed a high dose load on the rectal wall: the D2cc value (dose delivered to 2 cm 3 rectum) was EQD2 α / β=3Gy = 74.8 Gy, which is quite close to the recommended limit for this indicator, which is 75 Gy.

[0022] The distance between the rectal wall and the posterior vaginal wall of this patient, measured during preparation for the procedure, was 2.7 mm. In order to reduce the radiation dose to the rectal wall, 10 ml of a biodegradable spacer was introduced into the rectovaginal fat tissue between the posterior vaginal wall and the anterior rectal wall in the projection of the implantation point before brachytherapy. The introduction of the spacer allowed us to reduce the calculated value of D2cc α / β=3 = 50.4 Gy. The dosimetric benefit from using the spacer (1) relative to the load on the rectum (2) was 33%, which made it possible to deliver the SD to the residual cervical tumor (3) from the full course of radiation therapy of 93.5 Gy (Fig. 4).

[0023] Clinical example 2. Patient D., 29 years old. Clinical diagnosis: Cervical cancer stage IIBr T2bN0M0. PGI from 03 / 12 / 2025 moderately differentiated non-keratinizing squamous cell carcinoma.

[0024] Multidisciplinary oncology council from March 31, 2025, chemoradiation therapy. From March 31, 2025 to May 1, 2025, conformal radiation therapy was performed on a linear accelerator using fixing devices, volumetric visualization of the target SD = 46 Gy, against the background of weekly administration of Carboplatin, SD 964 mg. The next stage was brachytherapy. MRI topometry was performed using a ring applicator. Irradiation target volume: GTV, HR-CTV, IR-CTV. Preliminary calculation of the dosimetry plan before spacer insertion was performed on the Brachy Vision™ treatment planning system. The calculated data showed a high dose load exceeding the tolerance of the rectal wall: the D2cc value was EQD2 α / β=3Gy = 79 Gy.

[0025] The distance between the rectal wall and the posterior vaginal wall was 3.5 mm. To reduce the radiation dose to the rectal wall, a 5 ml spacer (8) was inserted before brachytherapy. The insertion of the spacer allowed us to reduce the calculated value to D2cc α / β=3 50.8 Gy, while bringing the SD to the residual cervical tumor from the full course of radiation therapy to 85.6 Gy (Fig. 5). The dosimetric benefit from using the spacer relative to the load on the rectum was 36%.

[0026] Description of the figures.

[0027] Fig. 1. Determining the spacer implantation point.

[0028] Fig. 2. Insertion of a spacer under ultrasound control into the fatty tissue between the rectum and vagina.

[0029] Fig. 3. Insertion of spacer.

[0030] Fig. 4. Patient K., 35 years old. A spacer was inserted into the fatty tissue between the walls of the rectum and vagina.

[0031] Fig. 5. Patient D., 29 years old. A spacer is inserted into the fatty tissue between the walls of the rectum and vagina.

[0032] 1 - rectal wall

[0033] 2 - posterior vaginal wall

[0034] 3 - conditional plane of the cervix

[0035] 4 - projection point of the cervix

[0036] 5 - endorectal sensor

[0037] 6 - stepper

[0038] 7 - guide needle

[0039] 8 - spacer implanted

Claims

1. A method for reducing the radiation dose to the rectum during brachytherapy of patients with cervical cancer, which includes preliminary preparation of the patient, performing magnetic resonance imaging of the pelvis, assessing the residual tumor of the cervix, characterized in that the projection point of the cervix is ​​determined in the area of ​​​​the intersection of an imaginary parallel line corresponding to the plane of the rectum and a perpendicular line to the plane of the cervix, measuring the distance between the wall of the rectum and the vagina at this point; the spacer dose is calculated taking into account the thickness of the fatty tissue between the rectum and the vaginal wall: if the thickness is 3 mm or less, 10 ml of the spacer is introduced, if more than 3 mm, 5 ml of the spacer is introduced.

2. The method according to paragraph 1, characterized in that the spacer guide needle is inserted under ultrasound control into the fatty tissue between the rectum and the vagina in such a way that the needle reaches the projection point of the cervix, after which the spacer is inserted.

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