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Image Based Brachytherapy in Carcinoma Cervix Using Single Pre-Brachy MRI - A Single Institution Experience
Abstracts / Brachytherapy 14 (2015) S11eS106 optimized; they were normalized to point A. The purpose of this approach was to investigate if the shielding of the applicator results in a different protection rate using the optimized plans and plans normalized to point A. Results: The degradation of the CTV coverage was not noticed when the shielded applicator was used; the average change of the D90 was 0.19 % and 0.60 % for the optimized and point A normalized plans. The most affected organ with shielding in place was the rectum with an average decrease of D2 dose of 4.77 % for the optimized plans and 5.44 % for the plans normalized at point A. The effect of the shielding for one patient was noticeably low due to the unfavorable anatomy in respect to the position of the shields. When this patient was excluded from the analysis, the average decrease of D2 for the rectum was 7.45 % and 8.57 % in the first and second approach, respectively. The same level of protection was noticed for rectum D0.1 and D5, i.e. 7.21 % and 6.29 % for the optimized plan, and 9.31 % and 7.19 % for the point A normalized plans. The average alternation of the D2 for the bladder, sigmoid and bowel was not significant for the optimized plans. It was 0.36 %, 0.27 % and 0.51 % respectively. The similar values were noticed for the point A normalized plans, i.e. 0.18 %, 0.03 % and 1.19 %. Conclusion: The shielded applicators did not decrease the coverage of the CTVs. The D2 dose to the rectum was lower up to 8.4 % for the optimized plans and up to 9 % for the plans normalized to point A. It was noticed that the dose to the other OARs (bladder, sigmoid and bowel) was not significantly altered when the shielded applicators were used. However, the effect of the ovoids shielding was more pronounced in the plans normalized to point A rather than in the optimized plans. Since the level of the OARs protection is dependent on the patients’ anatomy when the shielded applicators were used in the planning, it is required to extend the study with a larger patients’ cohort for any additional conclusions.
GSOR16 Presentation Time: 11:45 AM Image Based Brachytherapy in Carcinoma Cervix Using Single Pre-Brachy MRI - A Single Institution Experience Biju Azariah, MBBS, DNB1, Susan Mathews, MBBS, DMRT, MD, DNB1, Raghu Kumar, PhD2, P.G. Jayaprakash, MBBS, DRM, MD, FICRO1. 1 Radiation Oncology, Regional Cancer Centre, Trivandrum, India; 2 Radiation Physics, Regional Cancer Centre, Trivandrum, India. Background: : Routine implementation of Protocol Image Guided Adaptive BT is not always feasible, especially in developing countries because of its labor intensiveness, time consumption and financial constraints. This study, which is conducted in centre with high turnover and limited resources, explores the feasibility of utilizing the tumor morphology data, from a pre Brachy MRI and incorporating it in the subsequent CT based brachytherapy treatment. Purpose: 1.To explore the feasibility of implementing image based BT for carcinoma cervix by contouring on CT images using 3D target measurements from Pre Brachy MRI and to study its dosemetric and clinical benefits. Materials and Methods: Data of 20 patients with locally advanced carcinoma cervix, registered between May - June 2011, who were treated with radical chemo RT followed by the 3D image based BT were analysed. All patients had Pre Brachy MRI pelvis taken (on a day prior to the 1 st BT sitting) with MR specifications, that will assist in contouring the HR CTV on CT images acquired on the day of BT with the applicator in situ. The topographic details of cervix with residual tumour (if present) were obtained from Pre Brachy MRI with respect to the central canal and external OS. On the day of Brachytherapy, after placement of applicator, CT images were taken. The position of the external OS (where the flange lies) and the position of the cervical canal (where the IU applicator lies) can now be identified in the simulation CT image. Now, the details of the dimensions of the cervix and the residual tumour which were obtained from the pre BT MRI is used to contour the HR CTV in the simulation CT (using the central canal and the external OS as the landmark). Contouring for OAR were done for rectum, sigmoid and bladder. Then optimization was done aiming to cover the HRCTV adequately with 100% isodose curve and to reduce the dose to OAR. We recorded the volumetric doses of both optimized and unoptimised standard plans of the
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HRCTV and OAR, and compared them to find out the dosimetric benefit obtained out of optimization. For each sitting, CT simulation and planning process was repeated. The same HR CTV measurements from Pre Brachy MRI were used to contour the HR CTV for all the three sittings, respecting anatomical barriers. Tumor progression was ruled out by clinical examination during subsequent brachytherapy sittings. We followed our patients for two years to report on the local control, morbidity and survival. Results: We observed that, using ‘3D tumor morphology from the Pre Brachy MRI’ to contour the HRCTV in the CT images, and thereby delivering an optimized 3D brachytherapy treatment, is practically feasible, especially in a centre with high patient load and technological constrains. In patients with gross residual disease after EBRT, optimization significantly increased the HRCTV dose, meaning that these patients would have had inadequate coverage of target, if treatment was delivered with unoptimised standard plans. Significant reduction in bladder and rectal dose were obtained with optimization. Local control rates at 2 years were 100%.None of the patients had grade 3 or 4 bladder and rectal toxicities. Actuarial cancer specific survival and overall survival for all tumor stage and tumor size at 2y was 100%. Conclusion: This technique of delivering 3D BT with dose optimization could help in ensuring adequate target coverage and significantly reduce the OAR dose. This dosimetric benefit could translate into local control benefits and reduction in morbidity on longer follow up.
GSOR17 Presentation Time: 11:49 AM Is Three Dimensional Planning at Every Vaginal Cuff Brachytherapy Fraction Necessary? Dominique Martin, MSc, Audrey Roux, MD, Bernard Fortin, MD, MSc, Laurie Archambault, MSc, Michael Ayles, MSc, Caroline Duchesne, MSc, Laurent Tant^ot, MSc, Eve-Lyne Marchand, MD, PhD. Departement de Radio-Oncologie, H^opital Maisonneuve-Rosemont, Montreal, QC, Canada. Purpose: Three-dimensional (3D) computed tomography (CT) based planning for vaginal cuff high dose rate (HDR) brachytherapy(BT) allows to decrease dose to OARs without compromising target volume coverage. 3D-CTplan optimization at every fraction of vaginal cuff BT is however time and resource intensive compared to 2D-planning and therefore not easily feasiblefor all centers. The aim of this study was to evaluate if there was adosimetric advantage of 3D-CT plan optimization at every vaginal cuff HDR BT fraction. Materials and Methods: Ten patients with endometrial cancer treated with a combination of external beam radiation therapy (EBRT) and vaginal cuff HDRBT were randomly selected between December 2013 and July 2014. All patients had a planning CT scan prior to each BT fraction for 3D plan optimization. For every fraction, bladder was empty with indwelling catheter in place, the applicator size was constant with reproducible immobilization as well as leg positioning. Vaginal cuff HDR BT doses ranged from 11 Gy to 21 Gy in 2 to 3 fractions at 5mm depth. Dosimetry from 3D-CT plan optimization at each HDR BT fraction (optimized BT fractions) was compared to retrospectively generated dosimetry from importing fraction 1 HDR BT loading to the CT scans of subsequent BT fractions (non-optimized fractions). Dosimetric variations evaluated included CTV coverage (D90 and V100) and doses to OARs (D2cc). Results: CTV coverage goal of D90 ˃100% was respected for all plans and there was no significant difference in CTV coverage between the optimized and non-optimized HDR BT fractions. The range of variation observed between optimized and non-optimized fractions was 0 to 7.2% and 0 to 4.6% for D90 and V100respectively with an average D90 of 107.2% and V100 of 96.6% for optimized HDR BT fractions. Similarly there was no significant difference in the doses to the OARs between the optimized and non-optimized HDR BT fractions. For the optimized and non-optimized HDR BT fractions respectively, the average D2ccwere as followed: rectum 4.67Gy and 4.68Gy, bladder 4.46Gy and 4.49Gy, bowel 3.46Gyand 3.56Gy. Conclusions: While3D-CT plan optimization offers a dosimetric advantage compared to 2D-planning, our results suggest that for the majority of patients treated with a combination of EBRT and vaginal cuff HDR BT,
GSOR16 Presentation Time: 11:45 AM Image Based Brachytherapy in Carcinoma Cervix Using Single Pre-Brachy MRI - A Single Institution Experience Biju Azariah, MBBS, DNB1, Susan Mathews, MBBS, DMRT, MD, DNB1, Raghu Kumar, PhD2, P.G. Jayaprakash, MBBS, DRM, MD, FICRO1. 1 Radiation Oncology, Regional Cancer Centre, Trivandrum, India; 2 Radiation Physics, Regional Cancer Centre, Trivandrum, India. Background: : Routine implementation of Protocol Image Guided Adaptive BT is not always feasible, especially in developing countries because of its labor intensiveness, time consumption and financial constraints. This study, which is conducted in centre with high turnover and limited resources, explores the feasibility of utilizing the tumor morphology data, from a pre Brachy MRI and incorporating it in the subsequent CT based brachytherapy treatment. Purpose: 1.To explore the feasibility of implementing image based BT for carcinoma cervix by contouring on CT images using 3D target measurements from Pre Brachy MRI and to study its dosemetric and clinical benefits. Materials and Methods: Data of 20 patients with locally advanced carcinoma cervix, registered between May - June 2011, who were treated with radical chemo RT followed by the 3D image based BT were analysed. All patients had Pre Brachy MRI pelvis taken (on a day prior to the 1 st BT sitting) with MR specifications, that will assist in contouring the HR CTV on CT images acquired on the day of BT with the applicator in situ. The topographic details of cervix with residual tumour (if present) were obtained from Pre Brachy MRI with respect to the central canal and external OS. On the day of Brachytherapy, after placement of applicator, CT images were taken. The position of the external OS (where the flange lies) and the position of the cervical canal (where the IU applicator lies) can now be identified in the simulation CT image. Now, the details of the dimensions of the cervix and the residual tumour which were obtained from the pre BT MRI is used to contour the HR CTV in the simulation CT (using the central canal and the external OS as the landmark). Contouring for OAR were done for rectum, sigmoid and bladder. Then optimization was done aiming to cover the HRCTV adequately with 100% isodose curve and to reduce the dose to OAR. We recorded the volumetric doses of both optimized and unoptimised standard plans of the
S63
HRCTV and OAR, and compared them to find out the dosimetric benefit obtained out of optimization. For each sitting, CT simulation and planning process was repeated. The same HR CTV measurements from Pre Brachy MRI were used to contour the HR CTV for all the three sittings, respecting anatomical barriers. Tumor progression was ruled out by clinical examination during subsequent brachytherapy sittings. We followed our patients for two years to report on the local control, morbidity and survival. Results: We observed that, using ‘3D tumor morphology from the Pre Brachy MRI’ to contour the HRCTV in the CT images, and thereby delivering an optimized 3D brachytherapy treatment, is practically feasible, especially in a centre with high patient load and technological constrains. In patients with gross residual disease after EBRT, optimization significantly increased the HRCTV dose, meaning that these patients would have had inadequate coverage of target, if treatment was delivered with unoptimised standard plans. Significant reduction in bladder and rectal dose were obtained with optimization. Local control rates at 2 years were 100%.None of the patients had grade 3 or 4 bladder and rectal toxicities. Actuarial cancer specific survival and overall survival for all tumor stage and tumor size at 2y was 100%. Conclusion: This technique of delivering 3D BT with dose optimization could help in ensuring adequate target coverage and significantly reduce the OAR dose. This dosimetric benefit could translate into local control benefits and reduction in morbidity on longer follow up.
GSOR17 Presentation Time: 11:49 AM Is Three Dimensional Planning at Every Vaginal Cuff Brachytherapy Fraction Necessary? Dominique Martin, MSc, Audrey Roux, MD, Bernard Fortin, MD, MSc, Laurie Archambault, MSc, Michael Ayles, MSc, Caroline Duchesne, MSc, Laurent Tant^ot, MSc, Eve-Lyne Marchand, MD, PhD. Departement de Radio-Oncologie, H^opital Maisonneuve-Rosemont, Montreal, QC, Canada. Purpose: Three-dimensional (3D) computed tomography (CT) based planning for vaginal cuff high dose rate (HDR) brachytherapy(BT) allows to decrease dose to OARs without compromising target volume coverage. 3D-CTplan optimization at every fraction of vaginal cuff BT is however time and resource intensive compared to 2D-planning and therefore not easily feasiblefor all centers. The aim of this study was to evaluate if there was adosimetric advantage of 3D-CT plan optimization at every vaginal cuff HDR BT fraction. Materials and Methods: Ten patients with endometrial cancer treated with a combination of external beam radiation therapy (EBRT) and vaginal cuff HDRBT were randomly selected between December 2013 and July 2014. All patients had a planning CT scan prior to each BT fraction for 3D plan optimization. For every fraction, bladder was empty with indwelling catheter in place, the applicator size was constant with reproducible immobilization as well as leg positioning. Vaginal cuff HDR BT doses ranged from 11 Gy to 21 Gy in 2 to 3 fractions at 5mm depth. Dosimetry from 3D-CT plan optimization at each HDR BT fraction (optimized BT fractions) was compared to retrospectively generated dosimetry from importing fraction 1 HDR BT loading to the CT scans of subsequent BT fractions (non-optimized fractions). Dosimetric variations evaluated included CTV coverage (D90 and V100) and doses to OARs (D2cc). Results: CTV coverage goal of D90 ˃100% was respected for all plans and there was no significant difference in CTV coverage between the optimized and non-optimized HDR BT fractions. The range of variation observed between optimized and non-optimized fractions was 0 to 7.2% and 0 to 4.6% for D90 and V100respectively with an average D90 of 107.2% and V100 of 96.6% for optimized HDR BT fractions. Similarly there was no significant difference in the doses to the OARs between the optimized and non-optimized HDR BT fractions. For the optimized and non-optimized HDR BT fractions respectively, the average D2ccwere as followed: rectum 4.67Gy and 4.68Gy, bladder 4.46Gy and 4.49Gy, bowel 3.46Gyand 3.56Gy. Conclusions: While3D-CT plan optimization offers a dosimetric advantage compared to 2D-planning, our results suggest that for the majority of patients treated with a combination of EBRT and vaginal cuff HDR BT,