Clinical outcomes of adaptive intracavitary and interstitial brachytherapy technique in locally advanced cervical cancer: A real-world data.

PURPOSE: To evaluate clinical outcomes of CT-based adaptive intracavitary and interstitial brachytherapy (IC followed by IC-ISBT) in locally advanced cervical cancer (LACC) in resource-constrained settings. METHODS AND MATERIALS: LACC patients treated with adaptive brachytherapy techniques were analyzed to evaluate treatment characteristics and clinical outcomes. The Kaplan-Meier method was used for survival analysis, and the log-rank test for univariate analysis. RESULTS: Out of 141 eligible patients with LACC, 87 (61.7%) patients received external beam radiotherapy (EBRT) in referral hospitals, while 54 (38.3%) were treated at our center. We divided our cohort into two groups: poor EBRT responder group (n = 70 [49.6%]) where IC-ISBT was adapted to achieve optimum tumor doses and OAR optimization group 71 (50.4%) where IC-ISBT was performed to reduce OAR doses. Median HRCTV-D90 dose was 88 Gy (range 70-109 Gy) with median HRCTV volume 33cc (range 15-96). Median D2cc doses to OARs were 90 Gy (range 70-107), 71 Gy (range 55-105) and 70 Gy (range 47-90) to bladder, rectum and sigmoid, respectively. At median follow-up of 32 months, 3-year local control (LC), locoregional control (LRC), disease-free survival (DFS) and overall survival (OS) were 83%, 75%, 64% and 72%, respectively. Subgroup analysis revealed significantly better outcomes for OAR optimization compared to poor EBRT responders, with 3-year LC (95% vs. 70.1%, p < 0.001), LRC (87.3% vs. 62.7%, p < 0.001), DFS (79.2% vs. 49.4%, p < 0.001), and OS (86.2% vs. 57.4%, p < 0.001) CONCLUSION: In resource-constrained settings, implementation of Adaptive IC-ISBT is a viable alternative for optimizing OAR doses in LACC. However proactive approach employing IC-ISBT for tumor dose-escalation from first fraction of BT is warranted for improving LC in poor EBRT responders.

Reirradiation with advanced brachytherapy techniques in recurrent GYN cancers.

PURPOSE: To evaluate clinical outcomes of recurrent gynaecological cancers treated with reirradiation (reRT) using advanced brachytherapy (BT) technique. METHODS AND MATERIALS: Seventy-six women who underwent reRT with BT for gynaecological cancers at our institute between January 2000 and December 2019 were analysed to determine patient, disease and treatment characteristics and clinical outcomes. Descriptive analysis was used for demographics, and the Kaplan Meir method was used for survival analysis. RESULTS: Median age at recurrence was 55 years (Range: 35-73). Forty-three patients had recurrent cervical cancer with intact uterus, and 33 had recurrent vault/vaginal cancers post adjuvant RT. Eight patients received EBRT prior to BT (Range: 30-50Gy). Twenty-two patients (28.9%) received salvage chemotherapy before consideration of brachytherapy. Brachytherapy application was done using MUPIT in 38, Vienna applicator in 20, Syed Neblett in 8, central vaginal cylinder in 3, multicatheter intravaginal applicator in 2, tandem-ovoids in 4 and Houdek applicator in 1 patient. Median cumulative EQD2 for all courses of radiation was 108 Gy (IQR 92-123 Gy). At median follow up of 39 months, local control (LC), progression-free survival (PFS) and Overall survival (OS) at 2-years was 60%, 56.3%, and 72.9 respectively. Patients who had recurrences beyond 2 years had significantly better OS compared to early recurrences. Patients who received BT doses >40 Gy had a higher LC and PFS. Grade 3 to 4 late rectal toxicity was seen in 10 (13%), bladder toxicity in 6 (8%) and vaginal fibrosis in 24 (31%) patients. CONCLUSION: The use of advanced BT approach in reirradiation setting is a feasible and safe option in treatment of post-treatment recurrent cervical, endometrial, and vaginal cancers.

Clinical outcomes of patients treated with template-based high-dose-rate interstitial brachytherapy boost for post-operative recurrent gynecological malignancies: A retrospective analysis.

Purpose: To report the clinical outcomes in patients treated with Martinez universal perineal interstitial template (MUPIT)-based interstitial brachytherapy boost for primary and recurrent vault and vaginal cancers, and to perform a comparative analysis with our previously published series of similar patients. Material and methods: One hundred and seventeen patients treated between January, 2009 and December, 2015 were evaluated. Descriptive statistics for the patterns of relapse, local recurrence-free survival (LRFS), disease-free survival (DFS), overall survival (OS), and late toxicities were carried out. Kaplan-Meier curves were used for survival analysis. All variables with the potential to affect outcomes were tested using log-rank test for statistical significance. Results: At a median follow-up of 63 months, LRFS, DFS, and OS at 3/5 years were 77.1%/74.7%, 61%/52%, and 72.3%/63.1%, respectively. Overall treatment time (OTT) of 56 days did not affect outcomes. Bulky tumors and OTT > 63 days adversely affected LRFS. Overall treatment time also significantly impacted DFS and OS. Grade 3-4 late bladder toxicities were observed in 1.7% patients, and grade 3-4 late rectal toxicities in 5% patients. Compared to our previous series, the outcome in the current series is better in terms of severe late toxicities (5% improvement in rectal toxicity, and 2.7% improvement in bladder toxicity) and OS by 10%. This could be attributed to the increasing use of concurrent chemotherapy and relative optimization strategies for organs at risk. Conclusions: Patients with primary and recurrent vault and vaginal cancers treated with high-dose-rate interstitial brachytherapy boost using MUPIT resulted in modest clinical outcomes and acceptable late toxicities. OTT was the most important factor affecting the outcomes.

Implementation and Challenges of International Atomic Energy Agency/American Association of Physicists in Medicine TRS 483 Formalism for Field Output Factors and Involved Uncertainties Determination in Small Fields for TomoTherapy.

PURPOSE: International Atomic Energy Agency published TRS-483 to address the issues of small field dosimetry. Our study calculates the output factor in the small fields of TomoTherapy using different detectors and dosimetric conditions. Furthermore, it estimates the various components of uncertainty and presents challenges faced during implementation. MATERIALS AND METHODS: Beam quality TPR20,10(10) at the hypothetical field size of 10 cm × 10 cm was calculated from TPR20,10(S). Two ionization chambers based on the minimum field width required to satisfy the lateral charge particle equilibrium and one unshielded electron field diode (EFD) were selected. Output factor measurements were performed in various dosimetric conditions. RESULTS: Beam quality TPR20,10(10) has a mean value of 0.627 ± 0.001. The maximum variation of output factor between CC01 chamber and EFD diode at the smallest field size was 11.80%. In source to surface setup, the difference between water and virtual water was up to 9.68% and 8.13%, respectively, for the CC01 chamber and EFD diode. The total uncertainty in the ionization chamber was 2.43 times higher compared to the unshielded EFD diode at the smallest field size. CONCLUSIONS: Beam quality measurements, chamber selection procedure, and output factors were successfully carried out. A difference of up to 10% in output factor can occur if density scaling for electron density in virtual water is not considered. The uncertainty in output correction factors dominates, while positional and meter reading uncertainty makes a minor contribution to total uncertainty. An unshielded EFD diode is a preferred detector in small fields because of lower uncertainty in measurements compared to ionization chambers.

Modified Houdek vault applicator for high-dose-rate brachytherapy: a technical report and case series.

PURPOSE: Treatment of isolated post-surgical vault recurrence of cervical and endometrial cancers in previously unirradiated patients includes external beam radiotherapy (EBRT) ± concomitant chemotherapy, followed by brachytherapy (BT) boost. Supra-vaginal component of vault disease often requires interstitial BT for optimal dose coverage. We describe technical details and preliminary case series using modified Houdek vault applicator (MHVA) developed at our institution for limited intra-cavitary plus interstitial high-dose-rate (HDR) vault BT. MATERIAL AND METHODS: Nineteen patients with vaginal vault recurrences received BT boost with MHVA between October 2015 and May 2018. All underwent BT application and CT-based BT planning after completion of EBRT ± concomitant chemotherapy. RESULTS: Median EQD2 of BT dose in patients with carcinoma cervix recurrence (n = 15, α/ß = 10) was 18.8 Gy, and in those with endometrial cancer recurrence was 22.08 Gy (n = 4, α/ß = 4.5). Median total EQD2 was 68.8 Gy and 72.08 Gy, respectively. Mean 2 cc of bladder, rectum, and sigmoid EBRT + BT doses (EQD2, α/ß = 3) were 65.38 Gy (±7.76), 63.37 Gy (±5.52), and 57.04 Gy (±4.45), respectively. At 6-8 weeks, 17 patients showed complete response (CR). With median follow-up of 20.5 months, 2-year overall survival was 95% (95% CI: 85.2-100.0%), and 2-year progression-free survival was 79.4% (95% CI: 61.0-97.8%). Late toxicities seen were grade 2 proctitis in 1 patient, grade 1 proctitis in 5, grade 2 urethritis in 1, grade 3 cystitis in 1, and recto-vaginal fistula in 1 patient (with disease controlled). Recurrence rate was 6.7 times higher in patients with post-EBRT disease greater than 10 mm (p = 0.01). CONCLUSIONS: MHVA is a simple solution for intra-cavitary and interstitial HDR-BT boost in isolated vault cancers post-surgery, achieving acceptable dosimetric parameters. Preliminary clinical outcomes and late toxicities are satisfactory.

Measurement of the small field output factors for 10 MV photon beam using IAEA TRS-483 dosimetry protocol and implementation in Eclipse TPS commissioning.

Dosimetry of small fields (SF) is vital for the success of highly conformal techniques. IAEA along with AAPM recently published a code of practice TRS-483 for SF dosimetry. The scope of this paper is to investigate the performance of three different detectors with 10 MV with-flatting-filter (WFF) beam using TRS-483 for SF dosimetry and subsequent commissioning of the Eclipse treatment planning system (TPS version-13.6) for SF data. SF dosimetry data (beam-quality TPR20,10(10), cross-calibration, beam-profile, and field-output-factor(F.O.F)) measurements were performed for PTW31006-pinpoint, IBA-CC01 and IBA-EFD-3G diode detectors in nominal field size (F.S) range 0.5 × 0.5cm2to 10 × 10 cm2with water and solid water medium using Varian Truebeam linac. However, Eclipse-TPS commissioning data was acquired using IBA-EFD-3G diode, and absolute dose calibration was performed with FC-65G detector. The dosimetric performance of the Eclipse-TPS was validated using TLD-LiF chips, IBA-PFD, and IBA-EFD-3G diodes. Dosimetric performance of the PTW31006-pinpoint, IBA-CC01, and IBA-EFD-3G detectors was successfully tested for SF dosimetry. The F.O.Fs were generated and found in close agreement for all F.S except 0.5 × 0.5cm2. It is also found that TPR20,10(10) value can be derived within 0.5% accuracy from a non-reference field using Palmans equation. Cross-calibration can be performed in F.S 6 × 6 cm2with a maximum variation of 0.5% with respect to 10 × 10cm2. During profile measurement, the full-width half-maxima (FWHM) of F.S 0.5 × 0.5cm2was found maximum deviated from the geometric F.S. In addition, Eclipse-TPS was commissioned along with some limitations: F.O.F below F.S 1 × 1cm2was ignored by TPS, PDD and profiles were dropped from configuration below F.S 2 × 2 cm2, and F.O.F which does not satisfy the condition 0.7 < A/B < 1.4 (A and B are FWHM in cross-line and in-line direction) have higher uncertainty than specified in TRS-483. Validation tests for Eclipse-TPS generated plans were also performed. The measured dose was in close agreement (3%) with TPS calculated dose up to F.S 1.5 × 1.5cm2.

Measurement of Total Scatter Factor for Stereotactic Cones with Plastic Scintillation Detector.

Advanced radiotherapy modalities such as stereotactic radiosurgery (SRS) and image-guided radiotherapy may employ very small beam apertures for accurate localized high dose to target. Accurate measurement of small radiation fields is a well-known challenge for many dosimeters. The purpose of this study was to measure total scatter factors for stereotactic cones with plastic scintillation detector and its comparison against diode detector and theoretical estimates. Measurements were performed on Novalis Tx™ linear accelerator for 6MV SRS beam with stereotactic cones of diameter 6 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm. The advantage of plastic scintillator detector is in its energy dependence. The total scatter factor was measured in water at the depth of dose maximum. Total scatter factor with plastic scintillation detector was determined by normalizing the readings to field size of 10 cm × 10 cm. To overcome energy dependence of diode detector for the determination of scatter factor with diode detector, daisy chaining method was used. The plastic scintillator detector was calibrated against the ionization chamber, and the reproducibility in the measured doses was found to be within ± 1%. Total scatter factor measured with plastic scintillation detector was 0.728 ± 0.3, 0.783 ± 0.05, 0.866 ± 0.55, 0.885 ± 0.5, and 0.910 ± 0.06 for cone sizes of 6 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm, respectively. Total scatter factor measured with diode detector was 0.733 ± 0.03, 0.782 ± 0.02, 0.834 ± 0.07, 0.854 ± 0.02, and 0.872 ± 0.02 for cone sizes of 6 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm, respectively. The variation in the measurement of total scatter factor with published Monte Carlo data was found to be -1.3%, 1.9%, -0.4%, and 0.4% for cone sizes of 7.5 mm, 10 mm, 12.5 mm, and 15 mm, respectively. We conclude that total scatter factor measurements for stereotactic cones can be adequately carried out with a plastic scintillation detector. Our results show a high level of consistency within our data and compared well with published data.

Clinical outcome of high-dose-rate interstitial brachytherapy in vulvar cancer: A single institutional experience.

PURPOSE: With an aim to evaluate and report high dose date interstitial brachytherapy (HDR-ISBT) in vulvar cancers, we undertook this retrospective analysis. METHODS AND MATERIALS: Histologically proven vulvar cancers treated with HDR-ISBT between 2001 and 2016 were analyzed. Radiotherapy details, clinical outcome in terms of local control rates, survivals, and toxicities were evaluated. RESULTS: A total of 38 patients received HDR-ISBT, with definitive radiation in 29 (76.3%), adjuvant postoperative in six (15.8%) and salvage radiation in three (7.9%) patients. Of them, 29 patients received brachytherapy boost and nine patients ISBT alone. BT procedure included freehand plastic tube technique in 23 (single [n = 5] or multiple plane [n = 18]), 13 patients with template based and two patients combined approach. Patients with brachytherapy alone received median EQD2 of 38.4 Gy10 (35.5-46.7 Gy10), as boost received median 23.3 Gy10 (13-37.3 Gy10). At 3-month post-treatment response evaluation, 30 patients achieved clinically complete response, two patients partial response and six maintained postoperative status. With a median follow-up of 30 months, 29 (76.3%) were disease free, and 9 (23.7%) patients had relapsed disease with four patients expired due to disease and two died of other causes. The 5-year overall survival, disease free survival, and local control rates were 82%, 51%, and 77%, respectively. CONCLUSIONS: HDR-ISBT in vulvar cancer is a feasible and a viable option with acceptable and comparable outcomes.

Peripheral dose measurements with diode and thermoluminescence dosimeters for intensity modulated radiotherapy delivered with conventional and un-conventional linear accelerator.

The objective of this paper was to measure the peripheral dose (PD) with diode and thermoluminescence dosimeter (TLD) for intensity modulated radiotherapy (IMRT) with linear accelerator (conventional LINAC), and tomotherapy (novel LINAC). Ten patients each were selected from Trilogy dual-energy and from Hi-Art II tomotherapy. Two diodes were kept at 20 and 25 cm from treatment field edge. TLDs (LiF:MgTi) were also kept at same distance. TLDs were also kept at 5, 10, and 15 cm from field edge. The TLDs were read with REXON reader. The readings at the respective distance were recorded for both diode and TLD. The PD was estimated by taking the ratio of measured dose at the particular distance to the prescription dose. PD was then compared with diode and TLD for LINAC and tomotherapy. Mean PD for LINAC with TLD and diode was 2.52 cGy (SD 0.69), 2.07 cGy (SD 0.88) at 20 cm, respectively, while at 25 cm, it was 1.94 cGy (SD 0.58) and 1.5 cGy (SD 0.75), respectively. Mean PD for tomotherapy with TLD and diode was 1.681 cGy SD 0.53) and 1.58 (SD 0.44) at 20 cm, respectively. The PD was 1.24 cGy (SD 0.42) and 1.088 cGy (SD 0.35) at 25 cm, respectively, for tomotherapy. Overall, PD from tomotherapy was found lower than LINAC by the factor of 1.2-1.5. PD measurement is essential to find out the potential of secondary cancer. PD for both (conventional LINAC) and novel LINACs (tomotherapy) were measured and compared with each other. The comparison of the values for PD presented in this work and those published in the literature is difficult because of the different experimental conditions. The diode and TLD readings were reproducible and both the detector readings were comparable.

Dosimetric validation of new semiconductor diode dosimetry system for intensity modulated radiotherapy.

INTRODUCTION: The new diode Isorad was validated for intensity modulated radiotherapy (IMRT) and the observations during the validation are reported. MATERIALS AND METHODS: The validation includes intrinsic precision, post-irradiation stability, dose linearity, dose-rate effect, angular response, source to surface (SSD) dependence, field size dependence, and dose calibration. RESULTS: The intrinsic precision of the diode was more than 1% (1 σ). The linearity found in the whole range of dose analyzed was 1.93% (R² = 1). The minimum and maximum variation in the measured and calculated dose were found to be 0.78% (with 25 MU at ioscentre) and 4.8% (with 1000 MU at isocentre), respectively. The maximal variation in angular response with respect to arbitrary angle 0° found was 1.31%. The diode exhibited a 51.7% and 35% decrease in the response in the 35 cm and 20 cm SSD range, respectively. The minimum and the maximum variation in the measured dose from the diode and calculated dose were 0.82% (5 cm × 5 cm) and 3.75% (30 cm × 30 cm), respectively. At couch 270°, the response of the diode was found to vary maximum by 1.4% with ± 60 gantry angle. Mean variation between measured dose with diode and planned dose by TPS was found to be 1.3% (SD 0.75) for IMRT patient-specific quality assurance. CONCLUSION: For the evaluation of IMRT, use of cylindrical diode is strongly recommended.