Trans-rectal ultrasound-guided hybrid intra-cavitary and interstitial brachytherapy in carcinoma cervix: A feasibility study from a tertiary cancer center in India.

Purpose: To report the feasibility of performing hybrid intra-cavitary and interstitial (IC/IS) brachytherapy in patients with carcinoma cervix under trans-rectal ultrasound (TRUS) guidance. Material and methods: All patients who received an external beam radiotherapy (EBRT) dose of 50 Gy in 25 fractions with weekly chemotherapy, followed by a brachytherapy boost (21 Gy in 3 fractions) were prospectively included for analysis. IC/IS brachytherapy was performed using Fletcher style tandem and ovoid applicator with interstitial component under TRUS guidance. Parameters of implant quality analyzed included ability to insert tandem, ratio of needles loaded to the number of needles inserted, and incidence of uterine or organ at risk (OARs) perforation. Dosimetric parameters evaluated were dose to point A*, TRAK, D90 high-risk clinical target volume (HR-CTV), and D2cc to OARs (bladder, rectum, and sigmoid). Width and thickness of the target was compared between TRUS (TRUSw and TRUSt) and MRI (MRIw and MRIt). Results: Twenty carcinoma cervix patients treated with IC/IS brachytherapy were included for analysis. The mean HR-CTV volume was 36 cc. The median number of needles used were 6 (range, 2-10 needles). None of the patients had uterine perforation. Two patients had bowel and bladder perforation. The mean D90 HR-CTV and D98 HR-CTV were 87.3 Gy and 82 Gy EQD2, respectively. The mean D2cc to the bladder, rectum, and sigmoid were 80 Gy, 70 Gy, and 64 Gy EQD2, respectively. The mean dose to point A* was 70.4 Gy EQD2. The mean TRAK was 0.40. The mean TRUSw (±SD) and MRIw (±SD) were 4.58 cm (±0.44) and 4.49 cm (±0.50), respectively. The mean TRUSt (±SD) and MRIt (±SD) were 2.7 cm (±0.59) and 2.62 cm (±0.59), respectively. On statistical analysis, there was a significant correlation between TRUSw and MRIw (r = 0.93), and TRUSt and MRIt (r = 0.98). Conclusions: TRUS-guided IC/IS brachytherapy is feasible and provides adequate coverage of the target, with acceptable doses to OARs.

Dosimetric Impact of Air Pockets in the Vaginal Cuff Brachytherapy Using Model-based Dose Calculation Algorithm.

Background: Endometrial cancer is the most common disease of the female reproductive system. Vaginal cuff brachytherapy (VCB) has intrinsic advantages compared to external beam therapy when treated with radiation. A single-channel cylinder is a standard applicator in VCB. The present study aims to estimate a change in the dose to vaginal mucosa due to air pockets between the cylinder and vaginal mucosa by calculating with the Acuros BV algorithm and comparing it to the Task Group 43 (TG-43) algorithm. Materials and Methods: Patients who presented with air packets were included retrospectively. For each patient, three plans were created: the first plan used TG-43, the second plan used dose recalculation with Acuros BV, and the third plan was generated by re-optimization by Acuros BV. On the same axial computed tomography image, the point doses at the cylinder's surface and the displaced mucosa were recorded and the ratios were then estimated. Results: The average volume of air pockets was 0.08 cc (range of 0.01-0.3 cc), and 84% of air pockets displaced the vaginal mucosa by ≥0.2 cm. The average ratios of dose were 0.77 ± 0.09 (1 standard deviation [SD]) and 0.78 ± 0.09 (1 SD) for TG-43 and Acuros BV algorithms, respectively. Due to the air pocket, mucosa received a reduced dose by an average of 22.72% and an average of 23.29% for TG-43 and Acuros BV, respectively. The maximum displacement of mucosa and the ratio of doses were negatively correlated for both. In the Optimized Acuros BV plan, total dwell time increased by 1.8% but no considerable change in the dose ratios. Conclusion: The calculated dose of mucous membrane forced out of the cylinder surface by air pockets by the Acuros BV algorithm was nonsignificantly different from TG-43. Therefore, even in the presence of air pockets, the TG-43 algorithm for calculating the VCB dose is appropriate.

Comparison of dose delivered to vagina using two different intracavitary brachytherapy applicators for carcinoma cervix.

PURPOSE: The aim of the study was to compare the dose to vaginal points between two intracavitary applicators used for HDR brachytherapy in Carcinoma Cervix METHODS AND MATERIALS: Patients reporting to our center for Carcinoma cervix intracavitary brachytherapy were randomly allocated to treatment with either Manchester or Fletcher Suit Delclos (FSD) applicator. All patients received an EBRT dose of 50 Gy in 25 fractions along with weekly Cisplatin (40 mg/m2). Brachytherapy was administered using CT based planning. All patients received a dose of 7 Gy to Point A one week apart for a total of three fractions. For vaginal dose reporting, the PIBS points (PIBS, PIBS+1, PIBS+2, PIBS-1, PIBS-2) and dose to vagina at the level of ovoids was compared between the two applicators RESULTS: A total of 30 Carcinoma cervix patients were randomly allocated to receive intracavitary brachytherapy with either Manchester or FSD applicator. The mean vaginal reference length for patients treated with Manchester applicator was 4.3 and for patients treated with FSD applicator was 4.4. On analyzing dose to different vaginal points, patients treated with Manchester applicator received significantly higher mean and median doses to all PIBS points (except PIBS-2 cm) as compared to FSD applicator. On analyzing dose to the upper vagina at the level of the ovoids, the Manchester applicator delivered higher antero-posterior doses as compared to FSD applicator. CONCLUSIONS: Manchester applicator gives higher dose to the vagina as compared to FSD applicator for intracavitary brachytherapy in Carcinoma Cervix. The choice of using a particular applicator depends on the residual disease at the time of brachytherapy and patient anatomy.

Development of an indigenous low-cost multichannel cylinder applicator for vaginal tumors.

PURPOSE: The purpose of this study was to report our experience regarding the development of a low-cost multichannel vaginal cylinder applicator for superficial and recurrent vaginal tumors. METHODS AND MATERIALS: The applicator mold was created by applying heated wax sheets in layers around a plastic tube. Interstitial stainless-steel needles were placed at equal distance around the mold surface to create multiple channels for treatment. Two plans were created using CT images for a patient with a recurrent tumor over the posterior vaginal wall for comparing single-channel and multichannel cylinder dosimetry. The doses received by the target (high risk clinical target volume) and organs at risk (OARs) were computed using dose-volume histograms. RESULTS: There was no significant difference in terms of the prescribed dose delivered to high risk clinical target volume between the two plans. The volume of the target receiving 150 and 200 percent (V150 and V200) dose was higher in the multichannel cylinder plan than the single-channel cylinder plan. In terms of doses to the OARs, there was no significant difference between the rectum doses (D2cc rectum). There was a significant reduction in the dose to the bladder (D2cc bladder), urethra (D0.1cc urethra), and uninvolved vagina (D2cc uninvolved vagina). CONCLUSIONS: Multichannel vaginal cylinders reduce doses to the OARs as compared with the single-channel vaginal cylinder in superficial vaginal lesions limited to the wall of the vagina. Their use is limited by the cost of the applicator. Our low-cost multichannel vaginal cylinder can be used as a reliable alternative in such situations.

A Dosimetric Analysis of the Rectal Doses in Intracavitary Brachytherapy of Carcinoma Cervix: A Prospective Study from a Single Institute.

INTRODUCTION: Carcinoma cervix is a common gynecologic malignancy in India and is treated with radical chemoradiation where intracavitary brachytherapy (ICR) is an integral part. In ICR of cervix, the two-dimensional (2D) point-based dosimetry cervix is the most common method used in high-volume centers with rectal dose calculation at modified ICRU rectal point with rectal wire placement. The rectal dose measurement using this method underestimates the dose to the rectum, and rectal dose also varies with the type of applicator used. The aim of our study is to compare the rectal dose calculated by ICRU 38 method versus rectal dose calculated by the rectal wire method using Henschke applicator. MATERIALS AND METHODS: This is a single-institute, dosimetric comparison study done prospectively. Fifty patients were planned for ICR after 2D orthogonal radiograph-based, computer planning by iridium 192 high-dose rate remote afterloading technique after placing the appropriate Henschke applicator. The vaginal packing was done using sterile gauze with contrast material for defining the ICRU 38 rectal point, and a rectal wire was placed for the modified ICRU rectal point. Rectal doses were calculated by both the methods and compared. RESULTS: The modified ICRU rectal point recorded a lower rectal dose (mean of 25%) compared to ICRU 38 rectal point in the study patients. There were ten patients (20%) with either too much or too little contrast material which made the visualization of the rectal point and radiation planning difficult. P value by paired t-test method was 0.0001, which was statistically significant. CONCLUSION: The modified ICRU rectal point is easier to visualize than ICRU 38 method (100% vs. 80%) for dosimetry, but it underestimates the rectal doses when compared to ICRU 38 rectal point. There needs to be a correction factor applied (25% in our study for Henschke applicator) when evaluating the rectal doses calculated by rectal wire method, to reduce the rectal toxicity.

Study of positional dependence of dose to bladder, pelvic wall and rectal points in High-Dose-Rate Brachytherapy in cervical cancer patients.

The objective of the study is to examine the variation in doses to, Bladder, pelvic wall and Rectal Points when a patient is simulated in Supine (S Position) and Lithotomy M shaped positions (LM Position), respectively as part of Intracavitary Brachytherapy in Cervical Cancer patients. Patients (n = 19) were simulated and orthogonal images were taken in S Position and LM Positions on a physical simulator. Digital orthogonal X-ray images were transferred to Brachyvision Treatment Planning System via Dicom to generate treatment plans. Radio opaque dye of 7 ml was injected into the Foley bulb for identification and digitization of International Commission on Radiological Units and Measurements (ICRU) Bladder point. Pelvic side wall points were marked in accordance with ICRU 38 recommendations. A Rectal tube containing dummy source marker wire was used to identify Rectal Point. Students't-test was used to analyze the results. Doses in LM Position were lower and statistically significant when compared to S Position for ICRU Bladder Point, pelvic walls and Rectal Point. It was observed that movement of applicator could be the reason for the variations in doses between the two positions. Bladder, pelvic wall and rectal points systematically registered lower doses in LM Position as compared to S Position.