Dose at posterior-inferior border of symphysis point: A predictor for vaginal stricture in cervical cancer.

PURPOSE: To study the effect of various dose-volume parameters on the severity of vaginal stricture (VS) and the correlation of the latter with the posterior-inferior border of symphysis (PIBS) points in locally advanced cervical cancer patients treated with concurrent chemoradiation and brachytherapy. METHODS AND MATERIALS: A prospective study was done on 45 histologically proven locally advanced cervical cancer patients between January 2020 and March 2021. All of them were treated with concurrent chemoradiation with 6 MV photon linear accelerator to a dose of 45 Gy/25 fractions in 5 weeks. Twenty-three patients were treated with intracavitary brachytherapy with a dose of 7 Gy/fraction/week for three fractions. Twenty-two patients were treated with interstitial brachytherapy, with 6 Gy/fraction for four fractions, each fraction 6 h apart. Grading of VS was done as per Common Terminology Criteria for Adverse Events version 5. RESULTS: The median followup was 21.5 months. About 37.8% of patients had VS with a median duration of 8.0 months (4.0-12 months). About 22.2% had Grade 1, 6.7% had Grade 2, and 8.9% had Grade 3 toxicity. Doses at PIBS and PIBS-2 points had no correlation with vaginal toxicity, however, the dose at PIBS+2 was significantly associated with VS (p = 0.004). The treated length of the vagina at the time of brachytherapy (p = 0.001), initial tumor volume (p = 0.009), and vaginal involvement after completion of external beam radiotherapy (EBRT) (p = 0.01) were also statistically significant with the development of VS of Grade 2 or more. CONCLUSIONS: Dose at PIBS + 2, treated length of the vagina with brachytherapy, initial tumor volume, and post-EBRT vaginal involvement are strong predictors for the severity of VS.

Percutaneous high-dose-rate interstitial brachytherapy for non-resectable, chemo resistant malignant lesion of lung and liver.

PURPOSE: To explore the feasibility and efficacy of interstitial brachytherapy application for nonresectable and chemo-resistant malignant liver and lung lesions. MATERIALS AND METHODS: Percutaneous high-dose-rate interstitial brachytherapy (HDR ISBT) was applied in nine lesions of seven middle-aged patients with advanced carcinoma (five patients with liver lesion and two patients with lung lesion). All patients were surgically ineligible. All patients had already received systemic chemotherapy. Under computed tomography (CT) guidance (for lung lesion) or ultrasonography (USG) guidance (for liver lesion), a single stainless steel brachytherapy needle was inserted percutaneously in patients with lesion size ≤4 centimeter (cm) and multiple needles were inserted in patients of lesion size >4cm. A single dose of 15 Gy to 20 Gy with HDR ISBT was prescribed at the periphery of the lesion. The needles were removed just after treatment. Patients were kept under observation for 24 h after treatment. RESULTS: The median size of the lesion was 6.5 cm. In all the cases of liver lesion, more than 75% shrinkage of tumor volume in follow-up at 6 mo was observed. It was more than 50% for lung lesion. None of the patients had developed significant complications as on the median follow up period of 15 mo (ranges 3-27 mo). CONCLUSIONS: Percutaneous CT-guided high-dose-rate interstitial brachytherapy is a minimally invasive, safe, and feasible treatment option with minimal complication for inoperable, chemo resistant, advanced cancers with encouraging treatment outcomes.

A mathematical model to predict the different isodose volumes using TRAK value in HDR intracavitary brachytherapy for revised Manchester and ICRU-89 based Point A plans using computer tomography images.

Purpose: To find out the simple relationship between Total Reference Air Kerma (TRAK) and various isodose volumes. Calculated isodose volumes were compared with experimental data for revised Manchester and International Commission on Radiation Units and measurements (ICRU)-89 Point A-based treatment plans. The accuracy of the formula was compared with the results of other relationships available in the literature. Materials and Methods: Dosimetric data from 62 intracavitary brachytherapy (ICBT) treatment plans of 31 patients with cervical cancer were studied. Each patient had treatment plans normalized to revised Manchester and ICRU-89 Points A (Aflange and Aicru89). For each treatment plan, TRAK values, V350, V700, V1050, and V1400 were obtained. The modeling curve was plotted between Isodose volume (Vd) and the ratio of d/TRAK obtained from Aflange plans to get a mathematical relation. The results of this formula were compared with the experimental data and outcomes of other formulas available in the literature. A paired-sample t-test was performed to assess the statistical significance. Results: In the case of revised Manchester-based Aflange normalization plans, the mean isodose volume of V350, V700, V1050, and V1400 were 285.98 ± 32.3 cm3, 101.96 ± 10.63 cm3, 52.71 ± 4.72 cm3, and 31.44 ± 2.33 cm3 respectively. Likewise, for ICRU-89 based Aicru89 normalization plans, the mean isodose volumes of V350, V700, V1050, and V1400 were 304.11 ± 26.17 cm3, 108.88 ± 8.29 cm3, 56.62 ± 3.69 cm3 and 34 ± 2.23 cm3 respectively. The mean difference was significant. The Mathematical relationship developed was [INLINE:1]. No correlation was found between TRAK and D0.1cm3,D2cm3 for organs at risk. Conclusions: The developed formula calculated isodose volumes within the accuracy of ± 3% in ICBT plans.

Feasibility of using polytetrafluoroethylene flexible implant tube for interstitial brachytherapy patients.

PURPOSE: To design the different Polytetrafluoroethylene (PTFE) based flexible implant tubes using an in-house developed device and to evaluate them for High dose rate (HDR) interstitial brachytherapy using computer tomography images. METHODS AND MATERIALS: PTFE hollow tube having a 2 mm (6 French) outer diameter (OD) and 1.4 mm inner diameter (ID) was used to design in-house single and/or double leader flexible catheters for interstitial brachytherapy implant. An in-house Plastic Wire Drawing Plate (PWDP) machine was developed. Customization of PTFE hollow flexible implant tube (FIT) was done through PWDP. Different percentages of BaSO4 (5%, 10%, & 15%) were added to Nylon 6 to make radiopaque button. Various quality assurance tests were performed with the PTFE tubes implanted in the brinjal (phantom) before using them on the patients. That is, coupling of brachytherapy machine transfer tube with flexible PTFE Tubes, CT scan artifacts, tube kinks, breast template, and free-hand compatibility. RESULTS: With the help of the PWDP machine, plastic wires of different lengths were made for single leader and double leader tubes. The different plastic leader ends of 1 cm to 50 cm lengths having 1 mm diameter were created. The radiopaque button of Nylon 6 in circular shape having 1 cm diameter and 0.5 cm thick was created. Developed radiopaque buttons were visible on CT scan images as well as on radiograph images. CONCLUSIONS: PTFE tubes of the desired length can be made depending upon the size of the brachytherapy implant and are inexpensive than commercially available flexible implant tubes.

Development and validation of an indigenous, radiobiological model-based tumor control probability and normal tissue complication probability estimation software for routine plan evaluation in clinics.

Purpose: Development and validation of a simple and convenient computational program in MATLAB environment for estimating the tumor control probability (TCP) and the normal tissue complication probability (NTCP), as a decision support system for routine plan evaluation. Materials and Methods: We developed an in-house software using MATLAB 2016b (Mathworks) for estimating TCP and NTCP named as RBMODELV1. The program contains Niemierko free equivalent uniform dose (EUD) program code provided in authors research article. For rest of radiobiological (RB) models in the software separate coding is performed. The program accepts cumulative dose-volume histogram file in (.txt) format containing two columns dose and volume. A set of two RB parameters were prepared, default and user-dependent in excel sheet named as RBDATA. We cross-validated results of RBMODELV1 software with BioSuite software for Poisson's TCP model and Lyman-Kutcher-Burman (LKB) model. A set of total 20 patient's data of head and neck site took under study and respective TCP and NTCP calculated by all the RB models and compared. Results: This is the first study in which we tried to establish correlation between the mean doses (EUD) received by parallel structure (parotid gland and oral cavity) and predicted percentage of NTCP values. It is found that mean dose in the range of 35-40 Gy for parotid gland can result in more than 50% NTCP predicted by all four RB models. Similarly oral cavity receiving mean dose in the range of 53-58 Gy can results in more than 35% NTCP predicted by all the four models. There is <3% variation observed between TCP calculated by BioSuite and RBMODELV1 software and <4% variation observed between predicted NTCP for parotid gland and oral cavity OAR from LKB model by both the software. Conclusion: We created simple software RBMODELV1 which can be used as a research tool as well as decision support system.

A prospective randomized comparison of simultaneous integrated boost with sequential boost intensity-modulated radiotherapy in locally advanced head and neck cancer.

Purpose: A comparison of simultaneous integrated boost (SIB) with sequential boost (SEQ) using intensity-modulated radiotherapy along with concurrent cisplatin in locally advanced head and neck cancer (HNC) was made with regard to their survival outcomes and toxicity profile. Materials and Methods: A total of 34 patients were enrolled between October 2016 and March 2019. They were randomized into two arms, SIB and SEQB. All patients were treated with 6 MV photon beam on Linear Accelerator with weekly concurrent cisplatin at 35 mg/m2. Overall survival (OS) and disease-free survival (DFS) were the primary end points and acute and late toxicities were the secondary end points. Results: The median follow-up period was 40.6 and 37.3 months for SIB and SEQB, respectively. At the end of 5 years, the median OS was 40.6 and 37.3 months (P = 0.947) and the median DFS was 35.1 and 37.3 months in the SIB and SEQB arms, respectively (P = 0.991). Complete response at 3 months was 64.7% and 76.5% and partial response was 23.5% and 17.6%, whereas progressive disease was 11.8% and 5.9% in SIB and SEQB arms, respectively. Acute dermatitis, mucositis, dysphagia, and salivary gland toxicities were higher in the SIB arm compared to the SEQB arm. Conclusion: SIB and SEQ arms were comparable in terms of OS and DFS. However, the acute toxicities were higher in the SIB arm, although the difference was not significant, compared to the SEQB arm.

Evolution of Brachytherapy Applicators for the Treatment of Cervical Cancer.

Brachytherapy applicators have come a long way since Danlos developed early intracavitary applicators to treat cervical cancer patients. Therefore, this review will help in the neoteric designs of intracavitary applicators. A detailed literature survey of the gynecological brachytherapy applicators from the era of preloading to conceptual intensity-modulated brachytherapy applicators has been carried out. Depending on the extent of the disease and patient anatomy, the selection of brachytherapy applicators plays a pivotal role in the treatment of cervical cancer. Furthermore, the selection of the applicators is also based on the imaging modalities to be used for applicator reconstruction and treatment planning. Dose acceleration in the target and reduction in nearby organs at risk can be optimized using an applicator having the capabilities of intensity-modulated brachytherapy. Now, three-dimensional printed applicators are used for patient-specific tailor-made treatment and they are fast replacing the old conventional applicators. Newer advancements in technology have greatly influenced the neoteric designs of intracavitary brachytherapy applicators.

A comparison between revised Manchester Point A and ICRU-89-recommended Point A definition absorbed-dose reporting using CT images in intracavitary brachytherapy for patients with cervical carcinoma.

PURPOSE: This study is a comparison between revised Manchester Point A and International Commission on Radiation Units and measurements (ICRU) 89 report-recommended Point A absorbed-dose reporting in intracavitary brachytherapy for patients with cervical carcinoma. METHODS AND MATERIALS: The retrospective dosimetric study is based on the data of 32 patients with cervical carcinoma treated with high-dose-rate brachytherapy. Patients received 21 Gy in three fractions (7.0 Gy X three fractions) to Point A (Aflange, revised Manchester definition). All the patients were replanned with a new Point A (Aicru89) defined on CT images as per the American Brachytherapy Society/ICRU-89. The data collected were compared with the data obtained from Point A (Aflange). RESULTS: When using the Aflange plan normalization method, the mean dose of 0.1 cc, 1 cc, and 2 cc bladder volumes was 820.79 ± 207.47 cGy, 654.66 ± 152.69 cGy, and 588.91 ± 136.35 cGy, respectively. Likewise, when using the ICRU-89 Point Aicru89 normalization method, the mean dose of 0.1 cc, 1 cc, and 2 cc bladder volumes was 869.30 ± 224.67 cGy, 693.24 ± 166.20 cGy, and 616.61 ± 150.32 cGy, respectively. For the rectum, Point Aflange normalization plans, the mean dose of 0.1 cc, 1 cc, and 2 cc volumes was 589.37 ± 163.26 cGy, 487.51 ± 126.03 cGy, and 442.70 ± 111.43 cGy, respectively. Likewise, using the Aicru89 plan, the mean 0.1 cc, 1 cc, and 2 cc rectum volume was 625.07 ± 171.31 cGy, 517.50 ± 131.05 cGy, 464.94 ± 121.81 cGy, respectively. The statistical mean difference of Total Reference Air Kerma rate, V100 (cc), bladder, rectum and sigmoid, was found significant. CONCLUSIONS: It has been found that the position of revised Manchester (Aflange) and ICRU-89 Point A does not match on CT images/radiograph, which resulted in variation in doses to the tumor, V100 (cc), organ at risk, and Total Reference Air Kerma.

Comparison of two hypofractionated radiotherapy schedules in locally advanced postmastectomy breast cancer patients.

INTRODUCTION: The role of hypofractionated radiotherapy (HFRT) in postmastectomy breast cancer patients is not well established. This study was done to establish the role of two different HFRT schedules in the treatment of chest wall and regional lymph nodes after mastectomy. MATERIALS AND METHODS: Between 2012 and 2016, consecutively registered patients of locally advanced breast cancer patients having undergone mastectomy and adjuvant radiotherapy (RT) at a tertiary cancer center were analyzed. Locoregional recurrence (LRR) was the primary endpoint, whereas overall survival (OS), disease-free survival (DFS), and both acute and late adverse events were secondary endpoints. RESULTS: A total of 34 patients who were treated with 39 Gy in 13 fractions over 2½ weeks and 35 patients who were treated with 40 Gy in 15 fractions over 3 weeks were identified. The median follow-up period was 47 months and 63.5 months in the 39 Gy and 40 Gy arms, respectively. LRR was seen in 11.8% and 8.6% of patients in the 39 Gy and 40 Gy arms, respectively. OS at 4 years was 66% and 71.5% in the 39 Gy and 40 Gy arms, respectively. The mean DFS for 39 Gy and 40 Gy arms was 43.6 months and 66.4 months, respectively (P = 0.822). Acute skin toxicity was similar in the two groups. Arm edema was significantly more in the 40 Gy arm. CONCLUSION: The two HFRT schedules are equivalent to each other in terms of survival outcomes. Arm edema is higher with 40 Gy arm as compared to 39 Gy arm.

Small field depth dose profile of 6 MV photon beam in a simple air-water heterogeneity combination: A comparison between anisotropic analytical algorithm dose estimation with thermoluminescent dosimeter dose measurement.

AIM OF STUDY: To establish trends of estimation error of dose calculation by anisotropic analytical algorithm (AAA) with respect to dose measured by thermoluminescent dosimeters (TLDs) in air-water heterogeneity for small field size photon. MATERIALS AND METHODS: TLDs were irradiated along the central axis of the photon beam in four different solid water phantom geometries using three small field size single beams. The depth dose profiles were estimated using AAA calculation model for each field sizes. The estimated and measured depth dose profiles were compared. RESULTS: The over estimation (OE) within air cavity were dependent on field size (f) and distance (x) from solid water-air interface and formulated as OE = - (0.63 f + 9.40) x2+ (-2.73 f + 58.11) x + (0.06 f2 - 1.42 f + 15.67). In postcavity adjacent point and distal points from the interface have dependence on field size (f) and equations are OE = 0.42 f2 - 8.17 f + 71.63, OE = 0.84 f2 - 1.56 f + 17.57, respectively. CONCLUSION: The trend of estimation error of AAA dose calculation algorithm with respect to measured value have been formulated throughout the radiation path length along the central axis of 6 MV photon beam in air-water heterogeneity combination for small field size photon beam generated from a 6 MV linear accelerator.