High-dose-rate Intracavitary Brachytherapy Research Articles

A Comparative Study of Clinical Outcomes in Locally Advanced Cervical Cancer: External Beam Radiotherapy (EBRT) and Sequential High Dose Rate Intracavitary Brachytherapy (HDRICBT) with or without Concurrent Cisplatin on the Day of ICBT Insertion - A Tertiary Care Center Randomized Controlled Trial in India.

The current study aimed to delve into the comparative clinical outcomes between external beam radiation therapy (EBRT) and sequential High Dose Rate Intracavitary Brachytherapy (HDRICBT) with or without concurrent cisplatin administration on the day of intracavitary brachytherapy (ICBT) insertion in women with locally advanced cervical cancer. In this study, conducted between January 2017 and July 2018 at a leading institute in India, diagnosed and untreated patients of locally advanced carcinoma cervix were randomized into two groups. Arm 1 received concurrent cisplatin before each course of brachytherapy, while Arm 2 underwent brachytherapy alone. The outcomes were compared in terms of acute and late toxicities, treatment response, and follow-up. Data analysis was performed using SPSS 16, with statistical significance set at p < 0.05. Both study arms showed similar complete response (CR) rates of 73.3%, with no significant advantage of concurrent cisplatin before brachytherapy. However, a noteworthy trend emerged during follow-up. In the concurrent cisplatin group, the CR rate increased from 73.3% post 1 month of brachytherapy to 86.7% at 3 months and 83.3% at 6 months. Contrastingly, the control group showed CR rates of 73.3% post 1 month, 80% at 3 months, and 76.6% at 6 months. While not statistically significant, this observation suggests a possible enhancement in response rates with concurrent cisplatin and ICBT. Future studies focusing on the optimal drug, dosage, scheduling, and combining cisplatin with other agents are recommended to further explore the potential benefits observed in this study.

A comparative study between two different dose fractionation schedules of cobalt-60-based HDR intracavitary brachytherapy in carcinoma cervix stages IIB-IIIC1.

High dose rate (HDR) intracavitary brachytherapy (ICBT) is an integral element in the treatment of carcinoma uterine cervix. The main objective of brachytherapy in carcinoma cervix is to deliver a lethal dose to tumor cells without inducing unacceptable damage to the surrounding normal tissue. Because the absorbed dose falls off rapidly, higher doses can be safely delivered to the targeted tissue over a short time. The quest for optimum dose and fractionation schedule in HDR ICBT is still ongoing, and there is no uniform consensus. This study aimed to assess the acute dose-related toxicities of HDR brachytherapy schedule of 7 Gy x 3 fractions over 6 Gy x 4 fractions in the treatment of cervical cancer. The aim of this study was to study the acute treatment-related gastrointestinal (GI) and genitourinary (GU) toxicities between two HDR brachytherapy regimens. This is a prospective institutional study carried out from May 2018 to September 2018. In this time period, 66 patients of cervical cancers fulfilling our inclusion criteria were treated with concurrent chemoradiation (CCRT) following brachytherapy. During treatment, patients were randomized to arm A-7 Gy per fraction for three fractions and arm B-6 Gy per fraction for four fractions. Acute GI and GU toxicities were assessed using Common Terminology Criteria for Adverse Events (CTCAE) Version 4.03. All patients were kept for follow-up for 3 months in this study. There is no statistically significant difference between the two arms for acute GI and GU toxicities, and the results were comparable. Considering the increased hospital burden of locally advanced cervical cancer patients in the Indian context, the HDR brachytherapy schedule of 7 Gy per fraction is preferable to 6 Gy per fraction for a lesser fractionation schedule.

Compare Two Different Fractionated Regimes of HDR Intracavitary Brachytherapy after Concomitant Chemoradiation in Carcinoma Cervix: A Prospective Study

Background: Cervical cancer is the common cancer cause of death among women in developing countries. High Dose Rate (HDR) intracavitary brachytherapy that is given with or sequential after EBRT, is an integral component in the treatment of carcinoma of the cervix. In recent years, High Dose Rate (HDR) brachytherapy in combination with External Beam Radiotherapy (EBRT) has been popular in the management of carcinoma of the cervix. Objectives: To evaluate treatment response post 3 and 6 months after treatment completion and treatment-related toxicities during treatment in weekly v/s biweekly HDR intracavitary brachytherapy after concomitant chemoradiation in squamous cell carcinoma cervix patients. Methods: A total of 60 cervical cancer patients fulfilling the inclusion criteria were selected. Patients were randomly assigned to the weekly and Biweekly HDR ICBT using the chit-box method with replacement. Arm A (Study arm): 30 patients with concurrent EBRT (50 Gy/25 fractions with 2 Gy per fraction) with weekly cisplatin (35 mg/m2) followed by HDR-ICBT 5 Gy * 5 fractions biweekly after completion of EBRT. Arm B (Control arm): 30 patients with concurrent EBRT (50 Gy/25 fractions with 2 Gy per fraction) with weekly cisplatin (35 mg/ m2) followed by HDR - ICBT 7.5 Gy * 3 fractions weekly after completion of EBRT. Results: Patients were assessed at 3 and 6 months to determine the local disease response and the incidence of any toxicities assessed during the treatment. All responses were graded as either CR (complete response), PR (partial response), SD (stable disease), or PD (progressive disease). 30 patients were assessed for therapy response using the WHO criteria. At 3 months arm A showed 86% CR and arm B showed 90% CR. 2 patients in arm A and 1 patient in arm B had PR. In both arms 2 patients had progressive disease. At 6 months 1 patient in both arms who had progressive disease converted into partial response after taking post RT chemotherapy. Conclusions: To sum up, brachytherapy is a vital aspect of the process of treating cervical cancer. Several centers have experimented with various doses and fractionation regimes. Patients in the current trial reported no safety concerns or intolerability issues across any treatment protocol. Arm A had treatment completion before arm B with comparable disease response and toxicities. Therefore, the choice of treatment plan depends on the individual patient’s circumstances and the institution’s demands. nonetheless, longer follow-ups and a bigger patient sample are needed for a solid evaluation of disease response and toxicity.

Factors affecting the dosimetry of high-dose rate intracavitary brachytherapy in cervical cancer

Abstract Background: Intracavitary brachytherapy (ICBT) is essential in managing locally advanced cervical cancer. Brachytherapy as a modality has the advantage of a higher dose to the tumour with a dose fall off at the periphery as per the inverse square law. The dose per fraction is much higher than external beam radiotherapy. So proper application and dosimetry are of paramount importance to reduce late toxicity. Methods: A retrospective analysis of 69 patients who underwent three ICBT applications of 7 Gray in each fraction was done. The factors under consideration were the type of pain management (spinal anaesthesia (SA) versus conscious sedation (CS)), the initial size of the disease (bulky and non-bulky) and subsequent fractions (first fraction versus third fraction). The dosimetric parameters analysed were the doses received by points A, B and P and that of the critical organs (bladder, rectum and sigmoid colon). Results: The dose received by critical organs was comparable concerning all the factors under consideration. The dose to point P on the left side was significantly lower in the CS group than in the SA group (p-value = 0·031). Also, the dose to point P on the right side was significantly lower in the third fraction compared with the first fraction (p-value = 0·016). Conclusions: ICBT under spinal anaesthesia resulted in a higher dose to the pelvic wall. The initial size of the tumour or the subsequent fractions does not significantly affect the dose received by critical organs.

Image-guided high-dose-rate brachytherapy as the method of choice in medically inoperable early-stage endometrial cancer patients

PurposeAbout 3–9% of patients with endometrial cancer are unable to undergo surgery due to medical comorbidities, including morbid obesity, or age-related frailty syndrome. An alternative curative option is irradiation. The aim of this prospective study was to evaluate clinical outcomes of high-dose-rate intracavitary brachytherapy (HDR-ICBT) treatment in such patients. Materials and methodsSeventy-eight patients with FIGO stage I-II endometrial cancer disqualified from surgery were treated with HDR-ICBT with 45–52,5 Gy prescribed to high-risk clinical target volume (HR-CTV) in 5–9 fractions given once a week. All fractions were planned using computed tomography (CT) scans. ResultsThe median follow-up time was 67 months. Median age was 79 years (range: 42–93 years). Median body mass index (BMI) was 39,1 kg/m2 (range: 24,2–68 kg/m2). We observed no statistically significant impact of BMI ≥ 40 on overall survival (OS) or prgression free survival (PFS). The 3- and 5-year OS for the whole population were 69% and 55%, respectively. The impact of high risk features (FIGO II, grade 3 or type 2 cancer) on OS was significant (p = 0,049). The 5-year cumulative incidence of local failure, distant metastases and non-cancer death were 12,9% [95% CI: 5,4%–20,5%], 6,4% [95% CI: 0,9%–11,9%], 33,1% [95% CI: 22,3%–43,9%], respectively. The 5-year risk of cancer and non-cancer death were 9% (95% CI: 3%–16%) and 36% (95% CI: 25%–47%), respectively. We observed G1 vaginal apex stenosis only. ConclusionsCT-guided HDR-ICBT is a feasible and safe management of FIGO stage I endometrial cancer in obese and elderly patients. The survival outcome of the treated group is influenced more by associated comorbidities than by the progression of endometrial cancer.

Online Adaptive Magnetic Resonance-guided Radiation Therapy for Gynaecological Cancers: Preliminary Results of Feasibility and Outcome

AimsTo present the preliminary results on the clinical utilisation of an online daily adaptive magnetic resonance-guided radiation therapy (MRgRT) for various gynaecological cancers. Materials and methodsTwelve patients treated between September 2018 and June 2022 were included. Six patients (50%) were treated with pelvic radiation therapy followed by MRgRT boost as brachytherapy boost was ineligible or unavailable, three patients (25%) were treated with pelvic MRgRT followed by high dose rate brachytherapy, two patients (16.7%) were treated with only MRgRT, one patient (8.3%) was treated with linear accelerator-based radiation therapy followed by MRgRT boost for bulky iliac lymph nodes. ResultsThe median age was 56.5 years (range 31–86 years). Eight patients (66.7%) had a complete response, three patients (25%) had a partial response and one patient (8.3%) died due to acute renal failure. The mean follow-up time was 11.2 months (range 3.1–42.6 months). The estimated 1-year overall survival was 88.9%. The median treatment time was 47 days (range 10–87 days). During external beam radiation therapy, 10 (83.3%) patients had concomitant chemoradiotherapy. Pelvic external beam radiation therapy doses for all cohorts were 45–50.4 Gy with a fraction dose of 1.8 Gy. The median magnetic resonance-guided boost dose was 32 Gy (range 20–50 Gy) and fraction doses ranged between 4 and 10 Gy. Three patients were treated with intracavitary high dose rate brachytherapy (26–28 Gy in four to five fractions). None of the patients had grade >3 late genitourinary toxicities. ConclusionMRgRT is reliable and clinically feasible for treating patients with gynaecological cancers alone or in combination with brachytherapy with an acceptable toxicity and outcome. MRgRT boost could be an option when brachytherapy is not available or ineligible.

Vaginal Dose Reduction by Changing the Ovoid Loading Pattern in Image Guided Intracavitary Brachytherapy of Cervix.

Locally advanced cervical cancer is frequently treated using a combination of external beam radiotherapy and brachytherapy. Radiotherapy often leads to vaginal morbidity, which poses a significant problem. This study aims to analyze the impact of reducing ovoid loading on dosimetry. We analyzed forty-five CT-based intracavitary brachytherapy plans from fifteen patients. Three plan sets were created for the 45 applications: a standard loading plan (A), a plan with reduced ovoid loading (B), and a tandem-only loading plan (C). We generated Dose-Volume Histograms and recorded dose volume parameters for the three plan sets. The D90 for the Clinical Target Volume (CTV) did not show significant differences among the three plan sets (p = 0.20). The average D90 values for plans A, B, and C were 8.15Gy, 8.16Gy, and 7.4Gy, respectively. No statistically significant differences were observed in D2cc bladder (p = 0.09) (average values: 6.8Gy, 6.5Gy, and 5.9Gy for plans A, B, and C, respectively) and D2cc sigmoid (p = 0.43) (average values: 2.8Gy, 2.6Gy, and 2.4Gy, respectively) among the three plan sets. However, there was a statistically significant difference in D2cc rectum (p < 0.001) (average values: 4Gy, 3.3Gy, and 1.8Gy, respectively), as well as in vaginal dose points (p < 0.001). Reducing ovoid loading significantly decreased the doses to vaginal dose points and the rectum without compromising the dose to the Clinical Target Volume (CTV). Therefore, in carefully selected cases, the adoption of tandem-only loading or reduced ovoid loading could be considered to minimize vaginal morbidity following high dose rate intracavitary brachytherapy.

Dosimetric Investigation of Interstitial Versus Combined Interstitial with Intracavitary High Dose Rate Brachytherapy for Cervical Cancer

The purpose of the study was to evaluate clinical target (HR-CTV) coverage and OAR doses of ISBT and IS-ICBT brachytherapy techniques for cervix cancer. As this is a retrospective study, 11 patients treated from 2018 to 2022 were identified, ISBT (n=4) and IC-ISBT (n=7). Dose-volume histogram (DVH) from Oncentra Treatment Planning System and dosimetric parameters were analyzed and evaluated.The results showed the mean EQD2 of HR-CTV for both techniques were 89.1 ± 11.71 Gy while the mean EQD2 of D2cc for bladder, rectum and sigmoid were 88.9 ± 16.71 Gy, 81.2 ± 12.63 Gy, and 70.1 ± 15.95 Gy, respectively. For IC-ISBT technique, the mean EQD2 of HR-CTV was 91.5 ± 8.4 Gy which was slightly exceeds the dose constraints of 80 to 90 Gy based on ABS recommendation. HR-CTV volume that ranged from 34.93 - 168.33 cm3. The mean of CI was 0.90 and the mean of DHI for this technique was 0.36 ± 0.06. Meanwhile for ISBT technique, the mean HR-CTV volume range from 26.95 - 82.82 cm3. The mean EQD2 of HR-CTV was at 85.1 ± 16.75. The mean CI and DHI were at 0.85 ± 0.16 and 0.37 ± 0.1, respectively. As a conclusion, the mean EQD2 doses to the rectum (81.2 Gy) in both techniques slightly exceeded the limit from ABS recommendation. The mean DHI value was not quite significant different in both techniques. However, the IS-ICBT technique was more superior in conforming dose to HR-CTV based on higher CI value compared to ISBT alone.

Clinical outcome after high dose rate intracavitary brachytherapy with traditional point 'A' dose prescription in locally advanced carcinoma of uterine cervix: dosimetric analysis from the perspective of computed tomography imaging-based 3-dimensional treatment planning.

To analyze tumour response and toxicity with respect to cumulative radiotherapy dose to target and organs at risk (OARs) with computed tomography (CT)-based image guided adaptive brachytherapy planning for locally advanced carcinoma cervix. Patients were treated with two-dimensional concurrent chemoradiotherapy to whole pelvis followed by intracavitary brachytherapy (ICBT) with dose prescription to point 'A'. CT image-based delineation of high-risk clinical target volume (HR-CTV), urinary bladder, rectum and sigmoid colon was done with generation of dose-volume histogram (DVH) data and optimization of doses to target and OARs. Follow up assessments were done for response of disease and toxicity with generation of data for statistical analysis. One hundred thirty-six patients were enrolled in the study. Delineated volume of HR-CTV ranged from 20.9 to 37.1 mL, with median value of 30.2 mL. The equivalent dose in 2 Gy per fraction (EQD2) for point 'A' ranged from 71.31 to 79.75 Gy with median value of 75.1 Gy and EQD2 HR-CTV D90 ranged from 71.9 to 89.7 Gy with median value of 85.1 Gy. 69.2% of patients showed complete response and after median follow-up of 25 months, 50 patients remained disease free, of whom, 74.0% had received ≥85 Gy to HR-CTV D90 versus 26.0% receiving <85 Gy to HR-CTV D90. s Amidst the unavailability of magnetic resonance imaging facilities in low middle income countries, incorporation of CT-image based treatment planning into routine practice for ICBT provides the scope to delineate volumes of target and OARs and to generate DVH data, which can prove to be a better surrogate for disease response and toxicity.

External Beam Radiotherapy Interdigitated with High Dose Rate(HDR) Intracavitary Brachytherapy versus External Beam Radiotherapy followed by Sequential HDR Intracavitary Brachytherapy for Locally Advanced Carcinoma Cervix-Randomized Control Study.

In cervical cancer treatment, overall treatment time (OTT) is an important prognostic factor. This study compares the clinical outcomes when High-Dose-Rate Intracavitary-Brachytherapy(HDR-ICRT) is interdigitated with external beam radiotherapy(EBRT) versus sequential HDR-ICRT after EBRT in the treatment of locally advanced carcinoma cervix. Histologically confirmed carcinoma cervix patients [FIGO Stage IIB-IVA (except IIIC-2)] were included and randomized into two groups. The study group received EBRT 50Gy in 25 fractions with interdigitated HDR-ICRT 7Gy per fraction weekly for three fractions starting after completion of 3 weeks of EBRT or as soon as cervical os became negotiable thereafter. Patients in the control group received EBRT 50Gy in 25 fractions with sequential HDR-ICRT 7Gy per fraction weekly for three fractions starting one week after completion of EBRT. All patients were regularly followed up during and after radiotherapy for local toxicity and disease control. This study enrolled 102 patients; 51 in each arm. Median OTT in study and control arm were 46 and 60 days, respectively. Median follow-up duration was 24 months (two years). Loco-regional control after two years of follow-up was 84.31 % and 72.54% of patients in study arm control arm respectively (p-value 0.148). Two (3.92%) patients from study arm and eight (15.68%) from control arm had residual disease. Two patients in study arm and one from control arm had local recurrence. Two patients from study arm three patients from control arm developed distant metastases. RTOG mucosal grade III acute mucosal toxicity in either arm. Cervical-os negotiability was limiting factor for interdigitated HDR-ICRT. Interdigitated HDR-ICRT with EBRT may give local control with manageable toxicities as compared to sequential HDR-ICRT, with the advantage of significant reduction in OTT.<br />.

Prophylactic Para-Aortic Extended Field Irradiation with Concurrent Chemotherapy for FIGO Stage IIIC1 Cervical Cancer Using Intensity Modulated Radiotherapy Technique: Acute Toxicity and Dosimetric Assessment

To evaluate the efficacy of P - PART with concurrent chemotherapy in LACC with the use of intensity modulated radiotherapy technique (IMRT). Our Primary endpoint was to assess acute toxicities and secondary endpoint was to assess loco-regional control (LRC), disease free-survival (DFS), para-aortic recurrence free survival (PA-RFS). A total of 30 patients of squamous cell carcinoma of cervix with stage IIIC1 (FIGO-2018) were recruited in this prospective, single arm interventional phase II study between January 2021 to September 2022. 18FDG-PET CT was performed and those with positive PALN were excluded. IMRT was used to deliver a dose of 50 Gy in 25 fractions to whole pelvis and PALN chain below renal hilum till aortic bifurcation received 45 Gy in 25 fractions. Concurrent cisplatin was administered weekly at 40 mg/m2 during radiation. On completion of external beam radiotherapy, high dose rate intracavitary brachytherapy was given at 7 Gy per fraction in 3 fractions prescribed to HR-CTV. Acute toxicities were assessed using CTCAE version 5.0. Median age was 50 years (37-66 years). All patients had completed treatment as per protocol. All patients had positive pelvic nodes with the maximum nodal short axis dimension of 14 mm (10-18 mm). All patients had positive internal iliac group of LNs, only 2(6.6%) patients had positive common iliac group of Ln. Median number of concurrent cisplatin cycles given were 5 (3-5 cycle). Median overall treatment time was 56 days (52-63 days) and median follow up was 15 months (3-22 month). Median cumulative dose to HR-CTV was 84.3Gy (Range:79.2-86.9Gy). Cumulative median EQD2 to 2cc of bladder and rectum were 69.11Gy (Range:59.17 - 80.07 Gy) and 64.6 Gy (Range: 60.1-66.3Gy) respectively. 7(23.3%) patients having grade 3 diarrhea and 2(6.67%) patients had grade 3 anemia while no significant genitourinary or other toxicities were noted. Patient characteristics, dosimetric data are described in Table-1. All patients underwent clinical and radiological assessment at the time of last follow up with one (3.33%) patient experiencing local failure at 9 months of follow up, hence crude LRC rate is 96.6%, DFS is 13.5 months (5-22 months) and PA-RFS is 16 months (8-23 months) till last date of follow up. Prophylactic EFRT with concurrent chemotherapy using IMRT technique yielded excellent short term clinical outcomes with acceptable toxicity profiles. Longer follow up will elucidate late toxicity and long-term clinical outcomes.

Dosimetric Difference of Urinary Bladder and Rectum in Patients Undergoing Intracavitary Brachytherapy for Cervical Cancer under Procedural Sedation and General Anesthesia: A Survey at Bugando Cancer Center and Ocean Road Cancer Institute

Background: High-Dose-Rate Intracavitary Brachytherapy (HDR-ICBT) is a commonly employed treatment modality for cervical cancer, delivering a high dose of radiation directly to the tumor site while minimizing exposure to surrounding healthy tissues. Anaesthesia administration during HDR-ICBT varies, with some centres using Sedation (CS) and others employing General Anaesthesia (GA). Despite the widespread use of these anaesthesia techniques, their potential impact on dosimetric outcomes, particularly in the urinary bladder and rectum, remains an area of interest and investigation. Objective: This study aimed to determine the dosimetric difference in the urinary bladder and rectum doses among cervical cancer patients undergoing HDR-ICBT under CS and GA. The study was conducted at Bugando Cancer Centre (BCC) and Ocean Road Cancer Institute (ORCI) to compare the dosimetric outcomes between the two anaesthesia techniques. Methods: A total of 273 patients who underwent HDR-ICBT for cervical cancer were included in the study. Patients were divided into two groups based on the anaesthesia technique used during the procedure: 143 patients received GA, and 130 patients received CS. Dosimetric parameters of the urinary bladder and rectum doses were collected and analysed using descriptive statistics and the independent samples t-test. Results: The findings demonstrated a statistically significant dosimetric difference in the mean urinary bladder dose between patients treated under GA and CS (p &lt; 0.001). Patients under GA received a significantly lower mean urinary bladder dose compared to those under CS. However, no statistically significant difference was observed in the mean rectum dose between the two anaesthesia groups (p = 0.689). Conclusion: The study reveals that the choice of anesthesia technique significantly impacts the urinary bladder dose during HDR-ICBT for cervical cancer. Patients receiving GA had a lower mean urinary bladder dose compared to those under CS. However, no significant dosimetric difference was observed in the mean rectum dose between the two anesthesia groups. These findings emphasize the importance of considering anesthesia techniques during treatment planning to optimize dosimetric outcomes and patient safety in HDR-ICBT. Further investigation and long-term follow-up are warranted to validate and expand upon these results. Collaboration between radiation oncologists and anesthesia teams is crucial to enhance treatment efficacy and minimize potential complications during HDR-ICBT for cervical cancer

Dose and secondary cancer-risk estimation of patients undergoing high dose rate intracavitary gynaecological brachytherapy

Dose and secondary cancer risk of the breast and thyroid during high dose rate (HDR) brachytherapy for 100 gynaecological cancer patients have been estimated. The organ doses were measured using LiF thermoluminescence dosimeters LiF (TLD-100). Patient demographic data (i.e. age and body mass index (BMI)) were also collected and analyzed. Statistical significance (p-value = 0.04; 0.01; 0.01) was observed for the correlation between age and breast dose; body mass index (BMI) and breast dose as well as BMI and thyroid dose. The average breast dose for cervical, vaginal and endometrial cancers were 7.44, 8.03 and 10.72 mGy, respectively. The average thyroid dose for cervical, vaginal and endometrial cancers were 2.32, 2.95 and 3.02 mGy, respectively. Excess absolute risk of the breast increased with attainable age and excess relative risk of the thyroid decreased with age at exposure. It is recommended to intensify post-treatment follow-ups and optimize the doses to the breast and thyroid.

Comparison of two high dose rate intracavitary brachytherapy regimens in treatment of cervical cancer: a preliminary report

BackgroundTo assess and compare the local control and toxicities between HDR Intracavitary Brachytherapy with 7.5 Gy and 9 Gy per fraction after EBRT in treatment of carcinoma cervix.MethodologyA total of 180 patients were randomly assigned to 2 arms. Arm A received HDR intracavitary brachytherapy with a dose of 7.5 Gy per fraction, 1 fraction per week for 3 fractions and Arm B received 9 Gy per fraction, 1 fraction per week for 2 fractions. Patients were evaluated on follow up for assessment of local control and toxicities.ResultsThe median follow up was 12 months (6–18 months). In arm A 89% of the patient had complete response and 11% had recurrence or metastasis. In arm B 93% of the patient had complete response and 7% had recurrence or metastasis. Grade 2/3 diarrhoea was seen in 4.4% of patients in Arm A and in 7.7% in Arm B. Grade 2/3 proctitis was seen in 3.3% of patients in 7.5 Gy arm and in 6.6% in 9 Gy arm. One patient in each arm had grade 1 haematuria. The overall duration of treatment was significant lower in Arm B compared to Arm A (59 days vs 68 days, p = 0.01).ConclusionThe result of this clinical study shows that Intracavitary brachytherapy with a dose of 9 Gy per fraction is non inferior to other schedules in term of local control and does not result in increased toxicity.

Interfraction variations in doses at OARs during three-dimensional high dose rate brachytherapy planning of cervix cancer.

The American Brachytherapy (BT) Society recommends that BT must be included as a component of the definitive radiation therapy for cervical carcinoma because recurrences and complications are decreased when BT is used in addition to external beam radiotherapy. The aim of this study is to quantify the interfraction dose variations (VARacts) during high dose rate (HDR) BT, the effect of variation in dose in terms of excess "unrecognized" dose to OAR and to conclude the reason of the variation in reference of applicator position/geometry versus deformation of the organ at risk (OAR) concerned. Total 30 patients of carcinoma cervix, biopsy proven, between June 2018 and May 2019, were taken for the study. All patients were treated with external beam radiation therapy to a dose of 50 Gy in 25 fractions over 5 weeks, followed by three fractions of HDR intracavitary brachytherapy (ICBT) (7.5 Gy to point A in each fraction) by two-dimensional (2D) X-ray-based planning. Before treatment in the first and last fraction of BT, computed tomography (CT) scan was done for every patient. Then, a 3D-based planning was performed with CT images on our HDR Plus software with image sequence option. VARact was calculated. Rigid image registration of consecutive fraction images was used for quantification of the hypothetical variation in dose (VARhypo) arising exclusively due to changes in applicator placement and geometry. The mean contoured rectal volumes for the first and third fractions were 41.49 cc and 44.72 cc, respectively, while the respective volumes for bladder were 9.33 cc and 9.35 cc cm. These differences were statistically insignificant (P value: 0.263 and 0.919 for rectum and bladder, respectively). The mean equivalent dose in 2 Gy fraction (EQD2) bladder D2cc was 5.68 Gy and 5.79 Gy in the first and third fraction ICBT, respectively. The mean EQD2 for the rectal D2cc was 11.63 Gy and 12.85 Gy in the first and third fraction ICBT, respectively. None of the patients had an actual cumulative EQD2 more than 90 Gy for bladder, but 36.66% of the patients had a rectal dose exceeding the tolerance (75 Gy). Regression plots showed that VARhypo alone could predict about 42.2% of the VARact in the rectum and 19.2% of the VARact in the bladder. Thus, the remaining variation was due to the organ deformation-related dose variations between the two fractions. There were no statistically significant variations in the volumes or doses of OAR between the two fractions. However, a significant proportion of patients may have a higher dose to the OAR in the third fraction in the absence of individualized planning. This increase is likely to be more detrimental where higher doses per fraction are used. Variations in OAR doses may be caused by organ deformation and/or changes in applicator placement/geometry.

Dosimetric evaluation of the feasibility of utilizing a reduced number of interstitial needles in combined intracavitary and interstitial brachytherapy for cervical cancer.

To evaluate the ability of the Venezia advanced multichannel tandem and ring applicator to consistently produce dosimetrically comparable plans utilizing a reduced number of needle channels, to reduce the risk of secondary complications when boosting cervical cancer treatments with high dose rate (HDR) brachytherapy. We evaluated 26 fractions from 13 patients who were treated with HDR brachytherapy using the Venezia (Elekta) applicator. The original plans included a full load of 12-16 needles, including both parallel and 30-degree oblique needles. We replanned each original to nine new configurations, with a reduced number of two, three, four, or six needles. Comparisons included differences in percentage dose coverage to 90% of the high-risk clinical target volume, and percentage dose to 2cm3 of the bladder, rectum, sigmoid, and bowel. We considered new plans "passing" if they remained within our standards (D90>100%; D2cm3 <85% bladder, <65% rectum, sigmoid, bowel) or did not perform worse than original. Removing only the two most anterior or the two most posterior needles from both sides showed 80.8% and 61.5% overall passing rate. Removal of the most anterior and posterior four needles together showed 65.4% overall passing rate. Removing all oblique needles showed 19.2% overall passing rate. Removing only left-sided or only right-sided oblique needles showed 46.2% and 23.1% overall passing, respectively. Removing only right-sided or only left-sided parallel needles separately showed 19.2% and 34.6% overall passing, respectively. Removing all parallel needles showed 11.5% overall passing rate. As only two replans required a full needle load to maintain dosimetric quality and 40 (76.9%), 36 (34.6%), 18 (69.2%), and 10 (19.2%) replans passed with 2, 3, 4, and 6 needles removed respectively, this indicates the potential for using a lesser number of interstitial needles during combined intracavitary and interstitial HDR brachytherapy while maintaining dosimetric quality.

Influence of Bladder Volume on the Dose to the Target and Organs at Risk in High Dose Rate Intracavitary Brachytherapy of Cervix

Influence of Bladder Volume on the Dose to the Target and Organs at Risk in High Dose Rate Intracavitary Brachytherapy of Cervix

PO30 Presentation Time: 10:30 AM: Intracavitary Brachytherapy Using a Shielded Cylinder, Clinical Use and Patient Toxicity

<h3>Purpose</h3> The utility of shielded cylinder intracavitary brachytherapy applicators in clinical practice has not been reported. We evaluated patients treated using this applicator to report its use in clinical practice and toxicity following treatment. <h3>Materials and Methods</h3> This single institution retrospective study included all patients who received high-dose rate (HDR) intracavitary brachytherapy using a shielded cylinder applicator (#GM11003380, Varian Systems, Palo Alto, CA) as a component of treatment between July 2013-November 2021. Treatment parameters, dosimetry; tumor and treatment characteristics were abstracted from the medical record. Patient toxicities were collected prospectively through an institutional radiation toxicity database. <h3>Results</h3> A total of 48 patients received 188 HDR intracavitary brachytherapy treatments, with 157 using a shielded cylinder. The majority (90%) also received external beam radiation (EBRT) to a median dose of 4500cGy in 25 fractions (interquartile range, IQR, 4500-5625cGy). Common fractionations (fx) for brachytherapy included 2000cGy/4fx with EBRT for patients with recurrent uterine cancer, 2000-2800cGy/4fx with EBRT or 3000cGy/5fx without EBRT for patients with primary vaginal or vulvar cancer, and 500cGy/1fx with EBRT for rectal cancer patients. The median total EBRT + brachytherapy EQD2 was 6930cGy (IQR 6930-7900cGy). In the treatments delivered with a shielded cylinder, shielding was used to reduce dose to rectum (51%), uninvolved vagina (34%), and bladder/urethra (8%). The most common shielding pattern was 180° (78%) and 90° (20%), with a minority of treatments using 270° shielding (2%). In cases where shielding was used to reduce rectal dose, the D2cc[Gy] rectal dose in delivered plans was 1.18Gy (range 0.53 - 3.92Gy). In patients who had both unshielded and shielded treatment plans, the D2cc[Gy] rectal dose was reduced from 4.07Gy to 1.69Gy, respectively. The median total EQD2 rectal dose in patients who received EBRT in 25 fractions in addition to brachytherapy was 38.9Gy (range 14.8 - 47.8Gy). Acute grade 2-3 toxicities included dermatitis (9), cystitis (4), proctitis (3), fatigue (2), nausea (2), pain (2), and anemia (1). In patients who received brachytherapy alone there were no grade 2+ toxicities reported. Late grade 2-3 toxicities reported 6+ months after radiation therapy included vaginal stricture (4), vaginal dryness (1), fatigue (1), lower GI hemorrhage (1), lymphedema (1), urinary frequency (1), and urinary incontinence (1). One patient had a grade 3 vaginal fistula noted at 6-months. There was one grade 2 sacral insufficiency fracture noted at 4-months. There were no acute or late grade 4-5 toxicities. Median follow-up was 35 months (IQR 11-55 months). Fifteen patients died, 6 from cancer progression and 9 from non-cancer causes. Fifteen patients had cancer progression at a median of 28 months from completion of brachytherapy. Five patients had local-only failures, 9 patients had distant-only failures, and 1 patient had pelvic nodal failure. There was no difference in total EQD2 delivered to tumor between those patients who had local failure versus local control, with a median EQD2 of 69.3Gy and 69.5Gy, respectively. The location of local failure was in the unshielded area in three patients and involved the shielded area in two patients. <h3>Conclusions</h3> Shielded cylinder applicators can be utilized successfully in the treatment of well selected patients with primary and recurrent gynecologic cancers and rectal cancers, enabling dose reduction to non-target structures with low treatment-related toxicity.

Clinical Outcomes Following Definitive 3D Image-Guided HDR Intracavitary Brachytherapy for Medically Inoperable Endometrial Cancer

<h3>Purpose/Objective(s)</h3> Endometrial cancer (EC) is the most common gynecologic malignancy in the U.S. Brachytherapy alone or in combination with external beam radiation therapy (EBRT) is considered an alternative definitive treatment for women who are not surgical candidates, though limited data exists for outcomes with modern 3D image-guided brachytherapy. As the U.S. population ages and rates of obesity and other comorbidities rise, more women may require definitive radiation therapy. In this study, we report outcomes for a large cohort of patients treated with intrauterine brachytherapy with 3D CT-guided planning. <h3>Materials/Methods</h3> Retrospective review identified 59 women with EC who received high dose rate (HDR) intrauterine brachytherapy with dual or triple tandem applicators with definitive intent, alone or in combination with EBRT, between 2009-2020. All patients underwent endometrial biopsy and 92% had pretreatment diagnostic CT and/or MRI imaging. 3D CT-guided brachytherapy planning was done using planning software. Local failure-free survival (LFFS), disease-free (DFS), and overall survival (OS) estimates were calculated by Kaplan-Meier method. Median follow-up was 44 months (interquartile range [IQR], 17-88). <h3>Results</h3> Median patient age was 68 years (range, 37-87). Patients had atypical complex hyperplasia (15%), or clinical stage I (76%), II (5%), or III (3%) EC. Patients were ineligible for surgery due to medical comorbidities, including obesity (97% of patients), pulmonary disease (36%), cardiovascular disease (41%), renal disease (9%), or complicated prior surgical history (9%). Median BMI was 45.7 kg/m² (range, 17.2-79.7), and 64% of patients met criteria for severe obesity (≥40 kg/m²). Brachytherapy dose delivered ranged from 8.5Gy in 1 fraction to 36.5Gy in 5 fractions. Among patients receiving brachytherapy alone, 83% were treated with 34Gy in 4 fractions. 20% of patients underwent EBRT immediately prior to or following brachytherapy and received lower doses of brachytherapy. Median coverage of the uterus CTV V100 = 92% (range, 65%-99%). 5-year LFFS, DFS, and OS rates were 91%, 82%, and 75%, respectively. Median time to any failure was 15 months (IQR, 10-26). Among 59 patients, 4 failed locally, 3 failed in the peritoneum, and 2 failed both locoregionally and distally. Two of 4 patients who failed locally were successfully salvaged with surgery. Five patients died of EC. Ten patients (17%) had perforation of the uterus with applicator placement. Antibiotics were not given prophylactically and no patients developed bacterial peritonitis or other infectious complication. There was no correlation between perforation of the uterus at the time of brachytherapy and peritoneal spread of EC. <h3>Conclusion</h3> Outcomes following definitive 3D image-guided brachytherapy were excellent, with 5-year LFFS of 91% and 5-year DFS of 82%. Patients rarely died of EC. Our data supports the use of 3D brachytherapy as definitive therapy for patients who are not candidates for surgery.

14P A prospective study of comparision of two HDR brachytherapy regimens in treatment of cervical cancer

Cervical cancer is the 4th most common cancer in women in the world, and the 9th overall. External beam radiotherapy (EBRT) with concurrent cisplatin followed by brachytherapy forms the standard of care for advanced cervical carcinoma. High dose-rate (HDR) intracavitary brachytherapy (ICBT) for cervical cancer is now well established because of its numerous advantages. This study aimed to assess and compare the local control and toxicities between HDR ICBT with 7.5 Gy per fraction in three fractions (Control Arm) and 9 Gy per fraction in two fractions (Study Arm) after EBRT in treatment of carcinoma cervix.