RESUMO
PURPOSE: To investigate the isodose surface volumes (ISVs) for 85, 75 and 60â¯Gy EQD2 for locally advanced cervix cancer patients. MATERIALS AND METHODS: 1201 patients accrued in the EMBRACE I study were analysed. External beam radiotherapy (EBRT) with concomitant chemotherapy was followed by MR based image-guided adaptive brachytherapy (MR-IGABT). ISVs were calculated using a predictive model based on Total Reference Air Kerma and compared to Point A-standard loading systems. Influence of fractionation schemes and dose rates was evaluated through comparison of ISVs for α/ß 10â¯Gy and 3â¯Gy. RESULTS: Median V85â¯Gy, V75â¯Gy and V60â¯Gy EQD210 were 72â¯cm3, 100â¯cm3 and 233â¯cm3, respectively. Median V85â¯Gy EQD210 was 23% smaller than in standard 85â¯Gy prescription to Point A. For small (<25â¯cm3), intermediate (25-35â¯cm3) and large (>35â¯cm3) CTVHR volumes, the V85â¯Gy was 57â¯cm3, 70â¯cm3 and 89â¯cm3, respectively. In 38% of EMBRACE patients the V85â¯Gy was similar to standard plans with 75-85â¯Gy to Point A. 41% of patients had V85â¯Gy smaller than standard plans receiving 75â¯Gy at Point A, while 21% of patients had V85â¯Gy larger than standard plans receiving 85â¯Gy at Point A. CONCLUSIONS: MR-IGABT and individualized dose prescription during EMBRACE I resulted in improved target dose coverage and decreased ISVs compared to standard plans used with classical Point A based brachytherapy. The ISVs depended strongly on CTVHR volume which demonstrates that dose adaptation was performed per individual tumour size and response during EBRT.
Assuntos
Braquiterapia/métodos , Imagem por Ressonância Magnética Intervencionista/métodos , Radioterapia Guiada por Imagem/métodos , Neoplasias do Colo do Útero/radioterapia , Adulto , Idoso , Feminino , Humanos , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Dosagem Radioterapêutica , Neoplasias do Colo do Útero/patologiaRESUMO
PURPOSE: To demonstrate that V60 Gy, V75 Gy, and V85 Gy isodose surface volumes can be accurately estimated from total reference air kerma (TRAK) in cervix cancer MRI-guided brachytherapy (BT). METHODS AND MATERIALS: 60 Gy, 75 Gy, and 85 Gy isodose surface volumes levels were obtained from treatment planning systems (VTPS) for 239 EMBRACE study patients from five institutions treated with various dose rates, fractionation schedules and applicators. An equation for estimating VTPS from TRAK was derived. Furthermore, a surrogate Point A dose (Point A*) was proposed and tested for correlation with V75 Gy. RESULTS: Predicted volumes Vpred = 4965 (TRAK/dref) 3/2 + 170 (TRAK/dref) - 1.5 gave the best fit to VTPS. The difference between VTPS and predicted volumes was 0.0% ± 2.3%. All volumes were predicted within 10%. The prediction was valid for (1) high-dose rate and pulsed dose rate, (2) intracavitary vs. intracavitary/interstitial applicators, and (3) tandem-ring, tandem-ovoid, and mold. Point A* = 14 TRAK was converted to total EQD2 and showed high correlation with V75 Gy. CONCLUSIONS: TRAK derived Isodose surface volumes may become a tool for assessment of treatment intensity. Furthermore, surrogate Point A∗ doses can be applied for both intracavitary and intracavitary/interstitial BT and can be used to compare treatments across fractionation schedules.
Assuntos
Braquiterapia/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Neoplasias do Colo do Útero/radioterapia , Fracionamento da Dose de Radiação , Feminino , Humanos , Imageamento por Ressonância Magnética , Neoplasias do Colo do Útero/diagnóstico por imagemRESUMO
PURPOSE: Upfront quality assurance (QA) is considered essential when starting a multicenter clinical trial in radiotherapy. Despite the long experience gained for external beam radiotherapy (EBRT) trials, there are only limited audit QA methods for brachytherapy (BT) and none include the specific aspects of image guided adaptive brachytherapy (IGABT). METHODS AND MATERIALS: EMBRACE is a prospective multicenter trial aiming to assess the impact of (MRI)-based IGABT in locally advanced cervical cancer. An EMBRACE dummy run was designed to identify sources and magnitude of uncertainties and errors considered important for the evaluation of clinical, and dosimetric parameters and their relation to outcome. Contouring, treatment planning and dose reporting was evaluated and scored with a categorical scale of 1-10. Active feedback to centers was provided to improve protocol compliance and reporting. A second dummy run was required in case of major deviations (score <7) for any item. RESULTS: Overall 27/30 centers passed the dummy run. 16 centers had to repeat the dummy run in order to clarify major inconsistencies to the protocol. The most pronounced variations were related to contouring for both EBRT and BT. Centers with experience in IGABT (>30 cases) had better performance as compared to centers with limited experience. CONCLUSION: The comprehensive dummy run designed for the EMBRACE trial has been a feasible tool for QA in IGABT of cervix cancer. It should be considered for future IGABT trials and could serve as the basis for continuous quality checks for brachytherapy centers.
Assuntos
Braquiterapia/normas , Imageamento por Ressonância Magnética , Garantia da Qualidade dos Cuidados de Saúde , Radioterapia Guiada por Imagem/normas , Neoplasias do Colo do Útero/radioterapia , Fracionamento da Dose de Radiação , Feminino , Humanos , Estudos Prospectivos , Carga Tumoral , Neoplasias do Colo do Útero/patologiaRESUMO
PURPOSE: To validate the feasibility and use of dose points to characterize the bladder wall dose distribution and investigate potential impact of the applicator position in cervical cancer brachytherapy. METHODS AND MATERIALS: One hundred twenty-eight optimized MRI plans were evaluated. The International Commission of Radiation Units and Measurements (ICRU-38) point doses (B(ICRU)), surrogate for bladder base doses, were compared with D(2cc). Vaginal source to superior-anterior border of the symphysis distances were measured and compared within two groups, namely Group 1-B(ICRU)/D(2cc) ≥1 and Group 2-B(ICRU)/D(2cc) <1. Additionally, points at 1.5 and 2 cm cranial to the B(ICRU), parallel to the tandem and the body axis were analyzed. RESULTS: Thirty-seven percent of the patients had the ratio B(ICRU)/D(2cc) of 1 or higher, with the 2cc subvolume at the bladder base (Group 1). In 63%, BICRU/D2cc ratio was lower than 1 and the 2cc, cranial to the bladder base (Group 2). Median vaginal source-to-superior-anterior border of the symphysis line distance was -2 cm (range, -3.7 to +1.2 cm) in Group 1 and +1.8 cm (range, -2 to +4.8 cm) in Group 2 (+ cranial/- caudal direction). There was a high correlation between vaginal sources near the symphysis and the 2cc subvolume at the bladder base. The additional points provided no added value. CONCLUSIONS: Location of the 2cc subvolume varies in cervical cancer brachytherapy. Maximum doses are at the bladder base if vaginal sources are also in the vicinity of the bladder base indicated by B(ICRU)/D(2cc) ratio of 1 or higher. Such variation should be considered in dose-effect analyses and intercomparisons, as the same D(2cc) at different bladder locations may correlate with different morbidity profiles and severity Reporting D(2cc) and B(ICRU) doses together therefore remains essential.
Assuntos
Braquiterapia/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Bexiga Urinária/efeitos da radiação , Neoplasias do Colo do Útero/radioterapia , Relação Dose-Resposta à Radiação , Feminino , Humanos , Imageamento Tridimensional , Imageamento por Ressonância Magnética , Bexiga Urinária/patologia , Neoplasias do Colo do Útero/diagnósticoRESUMO
PURPOSE: Three-dimensional evaluation and comparison of target and organs at risk (OARs) doses from two traditional standard source loading patterns in the frame of MRI-guided cervical cancer brachytherapy for various clinical scenarios based on patient data collected in a multicenter trial setting. METHODS AND MATERIALS: Two nonoptimized three-dimensional MRI-based treatment plans, Plan 1 (tandem and vaginal loading) and Plan 2 (tandem loading only), were generated for 134 patients from seven centers participating in the EMBRACE study. Both plans were normalized to point A (Pt. A). Target and OAR doses were evaluated in terms of minimum dose to 90% of the high-risk clinical target volume (HRCTV D90) grouped by tumor stage and minimum dose to the most exposed 2cm³ of the OARs volume. RESULTS: An HRCTV D90 ≥ Pt. A was achieved in 82% and 44% of the patients with Plans 1 and 2, respectively. Median HRCTV D90 with Plans 1 and 2 was 120% and 90% of Pt. A dose, respectively. Both plans had optimal dose coverage in 88% of Stage IB tumors; however, the tandem-only plan resulted in about 50% of dose reduction to the vagina and rectum. For Stages IIB and IIIB, Plan 1 had on average 35% better target coverage but with significant doses to OARs. CONCLUSIONS: Standard tandem loading alone results in good target coverage in most Stage IB tumors without violating OAR dose constraints. For Stage IIB tumors, standard vaginal loading improves the therapeutic window, however needs optimization to fulfill the dose prescription for target and OAR. In Stage IIIB, even optimized vaginal loading often does not fulfill the needs for dose prescription. The significant dose variation across various clinical scenarios for both target and OARs indicates the need for image-guided brachytherapy for optimal dose adaptation both for limited and advanced diseases.
Assuntos
Braquiterapia/métodos , Neoplasias do Colo do Útero/radioterapia , Braquiterapia/efeitos adversos , Feminino , Humanos , Imagem por Ressonância Magnética Intervencionista , Estudos Multicêntricos como Assunto , Estadiamento de Neoplasias , Órgãos em Risco , Estudos Prospectivos , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador , Ensaios Clínicos Controlados Aleatórios como Assunto , Neoplasias do Colo do Útero/patologia , Vagina/patologiaRESUMO
BACKGROUND AND PURPOSE: This study evaluates the impact of MRI guided adaptive brachytherapy (BT) on uterine corpus dose. MATERIAL AND METHODS: 84 patients with median follow-up of 18 months were analysed. MRI based BT was done according to GEC-ESTRO guidelines. Non-involved uterine corpus at the time of BT was contoured and the uterine corpus dose (D90 and D98) was evaluated for (1) standard loading pattern with source loading to the tip of the tandem and (2) optimised dose plan. Tandem lengths and heights of the 85 Gy isodose were recorded. RESULTS: Dose optimisation resulted in a reduction of active tandem length of 0.4±0.4 cm leading to lowering the D90 to the non-involved uterine corpus from 63.8±9.5 Gy to 56.7±7.5 Gy EQD2 (p<0.0001). Mean active tandem length was 5.0±1.0 cm, and the height of the 85 Gy isodose was 5.7±1.0 cm in optimised plans. CONCLUSIONS: MRI guided dose optimisation lowered the dose to the uterine corpus. However, a total EBRT+BT dose larger than 50 Gy was obtained in 99% of patients. Assuming that 45-50 Gy is sufficient to eradicate microscopic disease, the lowering of uterus corpus dose is not expected to induce additional uterine corpus recurrences in the setting of MRI guided adaptive BT. This hypothesis should be tested in a larger number of patients as e.g. the EMBRACE study.