Rectum D2cc Research Articles

Stability of Intracavitary Applicator Placement for HDR Brachytherapy of Cervix Cancer

Introduction/BackgroundCervical cancer is often treated with a combination of external beam radiation therapy and high-dose-rate intracavitary brachytherapy. An intrauterine ring and tandem applicator is used for intracavitary brachytherapy. The dose is prescribed to the high-risk clinical target volume. The goals of this study were to investigate the stability of intracavitary applicator placement during patient transfer and to evaluate the dosimetric impact of displacement. MethodsFourteen patients with cervical cancer were analyzed. Three sets of orthogonal fluoroscopic radiographs were obtained in the high-dose-rate suite after the insertion and before treatment: pre–computed tomography (CT) fluoroscopic radiograph with patient in the lithotomy position, pre-CT fluoroscopic radiograph with patient in the legs down position, and post-CT fluoroscopic radiograph with patient in the legs down position. Applicator position after CT was compared with the pre-CT radiographs to determine if the position changed during patient transfer. The displacement was measured in the anterior-posterior, medio-lateral, and superior-inferior directions, as well as the degree of pitch, roll, and yaw. To study the impact of applicator shifts on dose to organs at risk (OARs), the ring and tandem applicator was shifted virtually in the BrachyVision treatment planning system. The OARs studied included the small bowel, sigmoid colon, rectum, and bladder. Five millimeter shifts were made in the superior-inferior, medio-lateral, and anterior-posterior direction. Three degree rotations were made in the pitch, yaw, and roll directions. Applicator shifts were analyzed in only one direction at a time. The dosimetric impact on OARs was evaluated by comparing the original and shifted/rotated plans to dose-volume histogram–based criteria. ResultsThe average displacements were 1.9 ± 0.5 mm laterally, 3.0 ± 0.6 mm longitudinally, and 9.5 ± 1.5 mm anterior-posterior. The average applicator rotation on the posterior-anterior radiograph was 1.0 ± 0.2° and 2.6 ± 0.6° on the lateral radiograph. Five millimeter anterior-posterior shifts had the greatest effect on dose to OARs. On average, 5 mm anterior shifts had the greatest effect on the small bowel dose, where there was a 13.7% (79.6 cGy) increase in D2cc. Five millimeter anterior shifts also affected bladder dose, with a 36.5% (141.1 cGy) increase in D2cc. Five millimeter POST shifts increased the rectal D2cc by 28.6% (168.7 cGy). Other directional shifts had negligible effects on dose. The largest effect on OAR dose arising from rotations was to the sigmoid colon, when the applicator rotated in the POST pitch direction. As a result, the dose increased by 4.7% (7.6 cGy). All other rotations had minimal impact on OAR doses. ConclusionPatient transfer resulted in applicator shifts and rotations that had a measurable effect on dose to OARs. The displacements were the result of either a direct shift or rotation of the applicator. Additional tracking of these shifts and rotations may clarify the sources of these unwanted motions and suggest possible mitigation strategies.

Impact of bladder volume on treatment planning and clinical outcomes of radiotherapy for patients with cervical cancer.

ObjectiveThis study aimed to investigate the impact of bladder volume on treatment planning and clinical outcomes of radiotherapy for patients with cervical cancer.Materials and methodsOne hundred and sixty-six patients with locally advanced cervical cancer were selected in this retrospective study. The patients were divided into four groups according to their average bladder volume during radiotherapy (external beam radiation therapy and intracavitary brachytherapy): group A: V<100 mL, group B: 100 mL≤V≤150 mL, group C: 150 mL<V≤200 mL, group D: V>200 mL. The bladder volume and the cumulative dose to planning target (D90), bladder (D2cc), rectum (D2cc), and sigmoid (D2cc) were calculated using the treatment planning system. Treatment outcomes including late adverse events (the maximum grade of radiation-induced proctitis and cystitis), the objective response rate of tumor and lymph node, overall survival (OS), and progression-free survival (PFS) were collected. Additionally, the correlation between bladder volume and the irradiated dose of organs at risk and treatment outcomes was analyzed.ResultsThe median follow-up time was 28 months. The D90 and D2cc of the rectum in group A were the highest (P<0.05). The D2cc of the bladder in group D was the highest (P<0.05). There was no significant difference in the tumor and lymph node regression rate, OS, and PFS among the groups. The difference in the late radiation-induced proctitis and cystitis maximum grade among the four groups was statistically significant (P<0.001, P=0.022, respectively), with group A the most serious and group B the mildest.ConclusionFor patients with cervical cancer, the bladder volume significantly affected the delivered dose to target, rectum, and bladder. When the bladder volume range was 100–150 mL, the rate of late radiation-induced proctitis and cystitis was low and the degree of reaction was mild. This is thought to be the optimum bladder volume for patients with cervical cancer during radiotherapy.

Appropriate Methodology for EBRT and HDR Intracavitary/Interstitial Brachytherapy Dose Composite and Clinical Plan Evaluation for Patients With Cervical Cancer

PurposeThis study assessed the appropriateness of full parameter addition (FPA) methods with respect to the 3-dimensional deformable dose composite method for evaluating combined external beam radiation therapy (EBRT) and intracavitary brachytherapy (ICBT). Methods and MaterialsA total of 22 patients who received EBRT and high-dose-rate ICBT were retrospectively evaluated. Split-ring and tandem applicators were used for all patients. Additional interstitial needles were used for 5 patients to supplement the implant. Deformable image registrations were performed to deform the secondary EBRT and ICBT planning computed tomography (CT) images onto the reference CT from the third fraction of ICBT. The Dice similarity coefficient was used to evaluate the quality of deformable registration. Doses were transferred to the reference CT, scaled to the equivalent dose in 2-Gy fractions and combined to create the dose composite. Eight dose-accumulation methods were evaluated and compared. D2cc and D0.1cc for organs at risk were investigated. ResultsThe differences in D2cc for rectum, bladder, sigmoid, and bowel between the FPA method for whole-pelvis EBRT and ICBT, calculated using an old American Brachytherapy Society worksheet (FPA_Eh + I_old) and deformable composite for EBRT with boosts and ICBT (Def_E + B + I) were –2.19 ± 1.37 Gyα/β = 3, –0.64 ± 1.13 Gyα/β = 3, –2.06 ± 2.71 Gyα/β = 3, and –1.59 ± 0.89 Gyα/β = 3, respectively. The differences in D2cc for rectum, bladder, sigmoid, and bowel between the new ABS worksheet (FPA_Eh + B + I_abs) and the Def_E + B + I method were 1.21 ± 1.22 Gy α/β = 3, 1.93 ± 1.38 Gyα/β = 3, 0.72 ± 1.12 Gyα/β = 3, and 1.19 ± 1.46 Gyα/β = 3, respectively. Differences in dose-volume histogram parameter values among Def_E + B + I and other FPA methods were not statistically significant (P > .05). ConclusionsCompared with the FPA-based method, deformable registration–based dose composites demonstrated lower OAR D2cc and D0.1cc values; however, the differences were not statistically significant. The current ABS-recommended FPA-based sheet can serve as an acceptable plan evaluation tool for clinical purposes.

Evaluation of variation of interfraction doses to organs at risk during brachytherapy of cervical cancer

BackgroundTwo-dimensional treatment planning using radiographs or simulator films was the standard in planning brachytherapy for patients with cervical cancer. Three-dimensional (3D) treatment planning has improved treatment efficacy. This retrospective study compares conventional and 3D treatment planning of brachytherapy in patients with cervical cancer and interfraction dose variation to bladder and rectum (D2cc). MethodsThe mean doses to bladder and rectum (D2cc) were computed by computed tomography (CT)–based planning during 100 sessions of intracavitary brachytherapy for carcinoma cervix with the same source configuration as generated for conventional planning, and these estimates were compared with the doses at International Commission on Radiation Units and measurements (ICRU) rectal, bladder points and point A. Interfraction variation of doses to bladder and rectum during various sessions was also analysed. ResultThe mean ICRU bladder dose and D2cc of the bladder for all patients was 3.7 Gy and 7.4 Gy, respectively (p < 0.001). The mean ICRU rectal dose from conventional plan was 4.3Gy and with CT planning, 4.45 Gy (p = 0.04). Interfraction dose variations for D2cc of the bladder were min −5.3 Gy and max 4.8 Gy and those of the rectum were min −1.8 Gy and max 1.72Gy. ConclusionDosimetric evaluation of conventional and 3D CT-based treatment planning for the same brachytherapy sessions demonstrated underestimation of ICRU bladder dose points (p < 0.001) and the rectal ICRU point dose and D2cc (p=0.04). The doses to organs at risk did not show a statistically significant variation between the fractions. However, large variation was noted between the interfractional maximum and minimum doses to bladder and rectum.

Outcomes after Definitive Re-Irradiation with 3D Brachytherapy with or without External Beam Radiation Therapy for Vaginal Recurrence of Endometrial Cancer

Abstract Background Limited outcome data exists on salvage re-irradiation for vaginal relapse of previously-irradiated endometrial cancer. We report our 10-year experience with management of vaginal recurrence using definitive intent re-irradiation brachytherapy with or without EBRT. Methods A retrospective review was performed on 22 patients treated with definitive-intent re-irradiation brachytherapy ± EBRT for vaginal recurrence of endometrial cancer. The cumulative rectosigmoid and bladder D2cc (EQD2) were limited to Results Prior radiation therapy consisted of vaginal brachytherapy (54.5%), pelvic EBRT (22.7%), or combination pelvic EBRT and brachytherapy (22.7%). Median re-irradiation interval was 26.6 months. Salvage re-irradiation consisted of EBRT with brachytherapy in 50.0% and brachytherapy alone in 50.0%. Median HR-CTV D90 (EQD2) was 64.5 Gy (IQR: 49.6–75.8). Median cumulative D2cc for bladder, rectum, and sigmoid were 72.1 Gy (range: 30.3–81.8), 70.6 Gy (range: 32.0–80.5), and 52.7 Gy (range: 29.6–75.3), respectively. At a median follow-up of 27.6 months, 3-year local control, regional control, disease-free survival, and overall survival rates were 65.8%, 76.6%, 40.8%, and 68.1%, respectively. There were no grade ≥ 3 acute or late rectosigmoid or bladder toxicities. Conclusion Re-irradiation with 3D conformal brachytherapy for vaginal recurrence is feasible and safe as long as cumulative dose to surrounding normal organs is limited, and offers a chance to potentially salvage 40% of patients presenting with vaginal recurrence in the setting of prior pelvic radiation.

Analysis of Volumetric Dosimetry of Target Volumes and Organs at Risk on ICRU Point-Based Dose Planning in CT-Guided HDR Intracavitary Brachytherapy to Carcinoma Cervix

Intracavitary brachytherapy (ICBT) has been historically planned based on orthogonal X-rays with point A as prescription point and surrogate rectal and bladder points to determine the approximate dose to organs at risk. This was standardized based on ICRU report 38. However, with the availability of better imaging modalities (CT, MRI), it became obvious that those points were poor surrogates for the tumor or the organ at risk. The current study analyzes the volumetric dose distribution to tumor volume and risk organs, from CT image-guided point-based planning done for intracavitary high-dose-rate brachytherapy using Fletcher–Suit–Delclos applicator in locally advanced carcinoma cervix patients. Fifty-one patients with locally advanced carcinoma cervix who were treated with ICBT were included. Point A-based dose planning was done based on CT images, on Oncentra™ treatment planning software. The doses to bladder point and rectal point were determined and were used for the purpose of dose prescription and optimization. Relevant target volumes and risk organ volumes were determined over the same plans, and dose measurements are taken. They were then analyzed for correlation and linear regression model using IBM SPSS Statistics version 23. The point A-based prescription dose did not adequately cover the target volume. CTV 90 obtained only 53.23% (95% CI 49.21–57.25) of the prescribed dose. The bladder point dose correlated well with all sub-volumes, especially D2cc bladder dose (r = 0.525, p = < 0.001). It satisfied linear regression model with standardized beta of 0.665. On the contrary, the correlation with rectal point and D2cc rectal dose was not strong (r = 0.284, p = 0.055). The point-based dose underestimates bladder dose by 18.24 ± 7.77% and overestimates rectal dose by 5.46 ± 4.55%, both being statistically significant. CT image-guided point A-based dose planning, without any volume-based optimization, has poor target volume coverage. There is disproportionate overestimation of dose to rectum and rectal wall while calculating from rectal point dose. The bladder point dose has good mathematical prediction for dose to bladder. However, volumetrically, it underestimates the actual dose. While point A-based planning on tomographic imaging can be a stepping stone toward image-guided brachytherapy, volume-based planning is necessary for optimizing the dose to primary tumor and managing risk organ dose properly.

Late toxicity after single dose HDR prostate brachytherapy and EBRT for localized prostate cancer: Clinical and dosimetric predictors in a prospective cohort study

PurposeTo describe the genitourinary (GU) and gastrointestinal (GI) late toxicity profile and to analyse the clinical and dosimetry outcomes predictors of the combination of EBRT and high-dose-rate (HDR) prostate brachytherapy (BT) for localized prostate cancer. Materials and methodsBetween January 2012 and May 2017, 210 patients were included in a prospective protocol. Treatment consisted in HDR-BT (15 Gy single fraction) plus 3DCRT (37.5 Gy/15 fractions). Univariate and multivariate logistic regressions were used to analyse the impact of variables on late toxicity. ResultsMedian age was 71 (56–82), 12.4% of patients had low, 44.3% intermediate and 41% high-risk prostate cancer. Median prostate volume was 28.4 cc. Median V100, V150, V200 were 98.2%, 27% and 7.4% respectively. Median urethra Dmax, rectum D1cc and D2cc, were 113.5%, 62.2%% and 54.2% respectively.After a median follow-up of 41 months (5–75) late G2 GU and GI late toxicity was observed in 14.8% and 5.2% of patients respectively. Late G3 GU and GI toxicity occurred in 0% and 1% of patients respectively.There were no outcome correlations with late G ≥ 2 GU toxicity on univariate analysis. Previous cardiovascular comorbidity (p = 0.042), and dose to the rectum D2cc (p = 0.016) and D1cc (p = 0.017) were associated with G ≥ 2 GI toxicity.Multivariate analysis showed that rectum D1cc (HR11.56; 95%CI 1.4–92.1; p = 0.021) and prior history of cardiovascular disease (HR3.6; 95%CI 1–12.9; p = 0.045) remained independent predictors of G ≥ 2 GI toxicity. ConclusionsThere is a low incidence of late GU and GI morbidity using single fraction HDR-BT and hypofractionated EBRT. Previous cardiovascular disease and dose to the rectum were observed to correlate with GI toxicity.

Incorporating Routine Magnetic Resonance Imaging-based Planning for the Delivery of High-dose-rate Brachytherapy for Prostate Cancer: An Evaluation of Clinical Feasibility and Dosimetric Outcomes.

IntroductionTo evaluate the implementation and dosimetric outcomes of magnetic resonance imaging (MRI) planning for improved target and normal tissue definition for the treatment of prostate cancer with high-dose-rate brachytherapy (HDRBT).MethodsFrom August 2015 to October 2017, 137 unique patients with newly diagnosed localized prostate cancer underwent a total of 174 outpatient brachytherapy procedures using MRI-based treatment planning. Patients receiving brachytherapy as monotherapy underwent two separate procedures while those receiving brachytherapy as a boost after external beam radiation therapy underwent a single procedure. The target volume was defined as the prostate +/- seminal vesicles as clinically appropriate without any additional margin. Pre-treatment dose-volume histogram (DVH) goals to the target were: D90≥95%, V90≥95%, V100≥90%, V150≤30%, V200≤15%. DVH goals to organs-at-risk (OARs): urethra D.01cc ≤115%, bladder D1cc ≤75%, rectum D1cc ≤75%, neurovascular bundle D0.1cc ≤100%, penile bulb D1cc ≤100%. Procedure times were recorded at each step of the procedure, from catheter insertion to removal.ResultsThe median target volume was 45.9 cc, the median volume receiving the prescription dose was 53.0 cc, and the median selectivity index was 0.9. The median values for target dosimetry were as follows: D90=99.9%, V90=95.7%, V100=90.1%, V150=28.1%, V200=10.5%. The median values for OAR dosimetry were: urethra D.01cc=114.3%, bladder D1cc=68.3%, rectum D1cc=51.8%, left neurovascular bundle D0.1cc=86.8%, right neurovascular bundle D0.1cc=88.5%, penile bulb D1cc=31.7%. The median time from catheter insertion to end of HDRBT delivery was four hours 14 minutes (range 2:56-9:08); total treatment package time was five hours 32 minutes (range 3:31-9:45).ConclusionRoutine MRI-based treatment planning is feasible for the delivery of HDRBT for prostate cancer. We met stringent dosimetric criteria despite more objective target and normal tissue definition with MRI imaging. Treatment package time remains reasonable. We have adopted MRI as our standard imaging modality for HDRBT for prostate cancer.

Evaluation of Volumetric Doses of Organs at Risk in Carcinoma Cervix Patients with HDR Intracavitary Brachytherapy and Comparison of CT-based and Conventional Plans.

Background:Brachytherapy treatment planning in cervix carcinoma patients using two dimensional (2D) orthogonal images provides only point dose estimates while CT-based planning provides volumetric dose assessment helping in understanding the correlation between morbidity and the dose to organs at risk (OARs) and treatment volume. Objective: Aim of present study is to compare International Commission on Radiation Units and Measurements Report 38 (ICRU 38) reference point doses to OARs with volumetric doses using 2D images and CT images in patients with cervical cancer. Material and Methods: In this prospective study, 20 patients with cervical cancer stages (IIB-IIIB) were planned for a brachytherapy dose of 7Gy per fraction for three fractions using 2D image-based treatment plan and CT-based plan. ICRU 38 points for bladder and rectum were identified on both 2D image-based plan and CT-based plan and doses (DICRU) at these points were compared to the minimum dose to 2cc volume (D2cc) of bladder and rectum receiving the highest dose. Results:D2cc bladder dose was 1.60 (±0.67) times more than DICRUb bladder dose whereas D2cc rectum dose was 1.13±0.40 times DICRUr. Significant difference was found between DICRUb and D2cc dose for bladder (p=.0.016) while no significant difference was seen between DICRUr and D2cc dose for rectum (p=0.964). Conclusion:The study suggests that ICRU 38 point doses are not the true representation of maximum doses to OARs. CT-based treatment planning is more a reliable tool for OAR dose assessment than the conventional 2D radiograph-based plan.

Hyaluronic gel injection into the vesicovaginal septum for high-dose-rate brachytherapy of uterine cervical cancer: an effective approach for bladder dose reduction.

PurposeThe purpose of this study was to report our initial experience of hyaluronic acid gel injection (HGI) in the vesicovaginal septum (VVS) for bladder dose reduction in brachytherapy (BT) for uterine cervical carcinoma.Material and methodsBetween September 2016 and May 2018, 15 uterine cervical cancer patients received HGI in the VVS as a part of their definitive radiotherapy (RT) treatment consisting of external beam radiation therapy (EBRT) with additional BT. Of those, 9 patients received BT both with and without HGI, and remaining 6 patients were excluded because these 6 patients received HGI in the VVS for all BT fractions. All 9 patients received HGI in the rectovaginal septum. For these patients, the dosimetric parameters bladder D2cc, HR-CTV D90, and rectum D2cc were selected, and two groups were generated (BT with vs. without HGI in the VVS) for dosimetric comparison.ResultsThe median cumulative EQD2 for HR-CTV, rectum D2cc, and bladder D2cc for the 9 patients were 73.3, 52.8, and 67.1, respectively. While no statistical difference could be detected for rectal dose reduction, bladder dose was significantly less in the group with HGI in the VVS compared to that without (449 cGy [range, 416-566, 1SD = 66.1] vs. 569 cGy [range, 449-647, 1SD = 59.5], p = 0.033), with no compromising of target coverage. Although it did not reach statistically significance, there was a trend toward better HR-CTV D90 in the group with HGI compared to that without HGI in the VVS (713 cGy vs. 706 cGy, p = 0.085). No severe bleeding, hematuria, bladder wall injury, or urethral injury requiring hospitalization was experienced in association with HGI in the VVS.ConclusionsHGI in the VVS can be performed safely and can effectively reduce the bladder dose in BT for uterine cervical cancer patients.

Dosimetric comparison of graphical optimization and inverse planning simulated annealing for brachytherapy of cervical cancer.

PurposeGraphical optimization (GO) and inverse planning simulated annealing (IPSA) are the main treatment planning optimization techniques used in patients undergoing 3D brachytherapy treatment. This study aims to compare the dosimetric difference of plans optimized by GO and IPSA in cervical cancer brachytherapy.Material and methods21 cervical cancer patients data sets consisted of computed tomography (CT) and magnetic resonance imaging (MRI), acquired with the Fletcher applicator in situ were transferred to the Oncentra brachytherapy planning system. For each patient, the treatment plan was initially optimized with GO to reach a maximal D90 tumor dose (6 Gy/fraction, 5 fractions), while keeping the dose to organs at risk (OARs) as low as possible. A second plan was then optimized with IPSA on the same CT images and data set (i.e., contours, catheters, and location of dwell points). Targets and OARs dose volume histograms and irradiation time were compared; data were analyzed with paired t-test; p value < 0.05 was considered statistically significant.ResultsThe plans with both optimizations meet the clinical requirements. The mean D90 of the clinical target volume was comparable for GO and IPSA. Similar values (p > 0.05) of target V100, V150, V200, HI, and CI were registered for GO and IPSA optimizations. Bladder and rectum D1cc and D2cc obtained by GO resulted in larger values than those obtained by IPSA (p = 0.002). V75 for bladder and rectum were slightly higher for IPSA, but without statistical difference (p > 0.05). The irradiation time was comparable (p > 0.05).ConclusionsIn 3D brachytherapy of cervical cancer, GO and IPSA optimizations do not present a significant difference in target dose coverage; nevertheless, IPSA may reduce the maximum dose to normal tissue when compared with GO.

Dosimetric comparison of 60Co and 192Ir high dose rate source used in brachytherapy treatment of cervical cancer.

The study purpose included dosimetric comparison of cobalt 60 (60Co) and iridium 192 (192Ir) high dose rate (HDR) source used in brachytherapy treatment of cervical cancer. Computed tomography (CT) scans for 15 patients of carcinoma of uterine cervix using 3-mm slice thickness were considered for the study The contouring of high-risk clinical target volume (HRCTV), bladder, and rectum on CT images was done as per the GEC ESTRO guidelines with the help of magnetic resonance imaging images in the treatment planning system. All parameters were kept the same for 60Co (3.5 mm active length, 0.5 mm active dia, Bebig) and 192Ir (3.5 mm active length, 0.6 mm active dia, Bebig) HDR source with 2.5-mm step size and dose prescription to Point A. As per the International Commission on Radiation Unit (ICRU)-89 guidelines, the dose-volume parameters such as D50(Gy), D90(Gy), and D98(Gy) for HRCTV and D0.1cc (Gy), D1cc (Gy), D2cc (Gy), and D5cc (Gy) to the bladder and rectum were calculated for both the HDR sources. The difference in dose-volume histogram parameters such as D50,D90,and D98 of HRCTV was 3.19%, 1.13%, and 0.50%, respectively, for the two radioisotopes. The difference in dose values of D0.1cc, D1cc, D2cc, D5cc, and ICRU reference points of bladder was -0.58%, -0.67%, -0.99%, -0.94%, and -1.75%, respectively. On the other hand, dose difference for D0.1cc, D1cc, D2cc, D5cc, and ICRU reference points of rectum was 0.67%, 0.26%, 0.56%, 0.63%, and -0.33%, respectively. The present study results show that all the dose parameters of HRCTV, bladder, and rectum with 60Co were comparable with those of 192Ir HDR source. The isodose distribution is more bulge out for 60Co in cranial-caudal direction compared to that of 192Ir. However, these differences can be reduced by treatment planning optimization techniques. The clinical plan evaluation in each slice and plane is necessary to explore the logistic and financial benefits of miniaturized 60Co source over 192Ir HDR source.

Comparison of volume doses from conventional two-dimensional brachytherapy with corresponding doses from three-dimensional magnetic resonance imaging-based brachytherapy in carcinoma cervix.

The purpose of this study was to evaluate the doses delivered to the brachytherapy (BT) target volume and organs at risk from two-dimensional X-ray-based plans on magnetic resonance imaging (MRI) and to compare these doses with the corresponding doses from the image-based optimized plans. Twenty patients with cervical cancer treated with chemoradiation and BT were included in this study. All patients had two sets of treatment plans generated for the first fraction of BT. Volume doses resulting from MRI-based optimized plans were compared with the corresponding doses from standard "Point A" prescription plans. There was statistically significant difference between the two planning modalities for the mean high-risk clinical target volume (HRCTV) D90 doses (P = 0.0014) although mean D2cc of bladder (P = 0.1667) and rectum (P = 0.051) was not different. Standard plans with a prescription dose of 7 Gy to Point A delivered a mean HRCTV D90 of 10.07 Gy in patients with no gross residual disease at the time of BT, which was very similar to the mean dose from MR-based plans (MRI 10.02 Gy and standard 10.07 Gy). The only factor seen affecting dose distribution in this group was the applicator geometry. Standard plans failed to deliver HRCTV D90 doses of >8.5 Gy in all patients with gross residual disease. The doses were <7.00 Gy to the HRCTV in three patients who had maximum residual diseases at the time of BT. Conventional X-ray-based plans with moderate Point A doses deliver HRCTV D90 comparable to MRI-based plans in patients with no residual disease, and centrally placed residual disease, provided proper applicator placement and ideal geometry can be ensured. Soft-tissue image-based BT dose optimization ought to be considered in all patients with gross residual disease at the time of brachytherapy.

Influence of dwell time homogeneity error weight parameter on treatment plan quality in inverse optimized high-dose-rate cervix brachytherapy using SagiPlan.

PurposeRestricting the gradients of dwell times between adjacent dwell positions can potentially be beneficial in reducing the probability of unwanted hot/cold spots occurring, if the planned applicators/anatomy relative positions change before or during treatment. This constraint, however, may degrade plan quality. This study, for the first time, aims to quantify the impact of modulation restriction on plan quality indices in inverse optimization for cervix high-dose-rate (HDR) brachytherapy using the BEBIG SagiPlan treatment planning system.Material and methodsTen cervical cancer patient plans were optimized for treatment with a BEBIG SagiNova 60Co HDR afterloader using the min/max inverse planning method, with dwell time homogeneity error weight (DTHEW) parameter values of 0 to 10. Dwell time homogeneity and gradients as well as various plan quality indices were analyzed.ResultsFor DTHEW = 0, min/max-based optimization yielded higher HR-CTV D90 values than the variance-based option (p < 0.001) and was therefore selected for this study. Averaging over all patients, selecting non-zero DTHEWs resulted in a general increase in dwell time homogeneity and decrease in mean and maximum adjacent dwell time gradients, especially between DTHEWs of 0 and 1. For DTHEW > 1, an increase of this parameter did not always result in more homogeneous dwell times or reduced gradients in individual patients. There was a negative correlation between DTHEW and both HR-CTV D90 and V100 (p < 0.001, r = –0.91). Increasing DTHEW also negatively affected conformity index (p < 0.001, r = –0.99). Changes in rectum and sigmoid colon D2cc were insignificant. There was a strong positive relationship between bladder D2cc and DTHEW (p < 0.001, r = 0.99).ConclusionsAssuming a static geometry, statistically significant degradation of plan quality can result from restricting the dwell time homogeneity in min/max-based optimization of cervix HDR brachytherapy plans using SagiPlan. Therefore, setting DTHEW to zero is indicated for the type of patient plans considered in this study.

Dosimetric effects of the Smit sleeve on high-dose-rate brachytherapy tandem and ovoids plans for patients with locally advanced cervical cancer.

PurposeSmit sleeves are used to facilitate insertion of the intrauterine tandem during brachytherapy for cervical cancer. When a tandem and ovoids system is used the base of the Smit sleeve displaces the ovoids distally. The dosimetric impact of this displacement is not known. Herein we performed a dosimetric analysis to quantify this impact on the integral dose and dose delivered to the organs at risk (OARs).Material and methodsEleven high-dose-rate brachytherapy plans in which a Smit sleeve was used with a tandem and ovoids were reviewed. A second set of plans was generated modifying the position of the ovoids to simulate absence of the Smit sleeve. The high-risk clinical tumor volume (HR-CTV) dose coverage was maintained the same for both sets of plans by appropriately rescaling the dwell times of the simulated plan. The mean integral dose, D2cc to the OARs (bladder, bowel, sigmoid and rectum) and the ICRU rectum point dose were compared between the original and modified plans using a paired two-sample t-test.ResultsSimulating removal of the Smit sleeve was associated with an average reduction in the mean integral dose of 6.1% (p < 0.001) and an average reduction of 10.9% (p = 0.004) to the rectal D2cc. Doses to the remaining OARs decreased to a lesser magnitude with only that of the sigmoid being statistically significant.ConclusionsThe use of a Smit sleeve with a tandem and ovoids system could lead to the delivery of a higher mean integral dose to achieve similar HR-CTV coverage. In addition, it could increase the dose to surrounding OARs, primarily the rectum. The clinical significance of these findings is unknown, but the potential dosimetric impact of using a Smit sleeve should be taken into consideration during the planning when this device is used.

Outcomes after definitive re-irradiation with 3D brachytherapy with or without external beam radiation therapy for vaginal recurrence of endometrial cancer

BackgroundLimited outcome data exists on salvage re-irradiation for vaginal relapse of previously-irradiated endometrial cancer. We report our 10-year experience with management of vaginal recurrence using definitive intent re-irradiation brachytherapy with or without EBRT. MethodsA retrospective review was performed on 22 patients treated with definitive-intent re-irradiation brachytherapy ± EBRT for vaginal recurrence of endometrial cancer. The cumulative rectosigmoid and bladder D2cc (EQD2) were limited to <75 Gy and <90 Gy, respectively. Kaplan-Meier and Cox proportional hazards modeling were used to estimate survival. Severe (grade 3 or higher) radiation-related toxicities, defined according to CTCAE v4, were recorded. ResultsPrior radiation therapy consisted of vaginal brachytherapy (54.5%), pelvic EBRT (22.7%), or combination pelvic EBRT and brachytherapy (22.7%). Median re-irradiation interval was 26.6 months. Salvage re-irradiation consisted of EBRT with brachytherapy in 50.0% and brachytherapy alone in 50.0%. Median HR-CTV D90 (EQD2) was 64.5 Gy (IQR: 49.6–75.8). Median cumulative D2cc for bladder, rectum, and sigmoid were 72.1 Gy (range: 30.3–81.8), 70.6 Gy (range: 32.0–80.5), and 52.7 Gy (range: 29.6–75.3), respectively. At a median follow-up of 27.6 months, 3-year local control, regional control, disease-free survival, and overall survival rates were 65.8%, 76.6%, 40.8%, and 68.1%, respectively. There were no grade ≥ 3 acute or late rectosigmoid or bladder toxicities. ConclusionRe-irradiation with 3D conformal brachytherapy for vaginal recurrence is feasible and safe as long as cumulative dose to surrounding normal organs is limited, and offers a chance to potentially salvage 40% of patients presenting with vaginal recurrence in the setting of prior pelvic radiation.

MRI-guided adaptive brachytherapy for locally advanced cervix cancer: Treatment outcomes from a single institution in Hong Kong

BackgroundParadigm has shifted from 2D to image-guided adaptive brachytherapy (IGABT) for locally advanced cervix cancer (LACC). Increasing reports from pioneering institutions and large retrospective multicenter series have demonstrated improvements in outcome and reduction in toxicity with IGABT. However, there is scarcity of data on magnetic resonance (MR)-IGABT in Chinese patients. PurposeTo evaluate the clinical outcome of MR-IGABT for LACC in a single institution in Hong Kong. Material and MethodsPatients with FIGO stage IB-IVA LACC treated with definitive external beam radiotherapy +/− concurrent cisplatin followed by MR-IGABT from January 2015 to January 2018 were included. Brachytherapy planning and dose reporting followed the GEC-ESTRO recommendations. Dosimetric and clinical outcomes including local control (LC), pelvic control (PC), cancer-specific survival, overall survival (OS), and toxicity were analyzed. ResultsForty-two consecutive patients were included. 71% were FIGO stage IIB or above; 52% had pelvic node involvement. Median high-risk clinical target volume (HRCTV) was 34.7 cm3 (12.3–155.1 cm3). Median dose to HRCTV D90 was 88.5 Gy (63.4–113.4 Gy) (EQD210). Median doses to the D2cc of bladder, rectum, sigmoid, and small bowel were 83.1 Gy, 67.5 Gy, 69.0 Gy, and 68.9 Gy (EQD23), respectively. Median followup was 20.3 months (4.0–35.1 months). 24-month actuarial LC, PC, cancer-specific survival, and OS were 90%, 84%, 90%, and 90%, respectively. Stratification by clinical variables showed that FIGO stage had significant impact on LC and dose to HRCTV on both LC and PC. Treatment was well tolerated without any severe late toxicity. ConclusionsIntermediate-term results from systematic MR-IGABT for LACC demonstrate very promising outcomes with minimal toxicity. This fills the gap in evidence for MR-IGABT in Chinese patients.

Dosimetric comparison of vaginal vault brachytherapy vs applicator-guided stereotactic body radiotherapy with volumetric modulated arc therapy and helical tomotherapy for endometrium cancer patients

We performed this dosimetric study to compare a nonstandard volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) techniques with high-dose rate (HDR) brachytherapy (BRT) plan of vaginal vault in patients with postoperative endometrial cancer (EC). Twelve postoperative patients with early stage EC were included in this study. Three plans were performed for each patient; dosimetric and radiobiological comparisons were made using dose-volume histograms and equivalent dose for determining the planning target volume (PTV) coverages in brachytherapy and external beam radiotherapy, and organs-at-risk (OARs) doses between three different delivery techniques. All the plans achieved adequate dose coverage for PTV; however, the VMAT plan yielded better dose conformity, and the HT plan showed better homogeneity for target volume. With respect to the OARs, the bladder D2cc was significantly lower in the BRT plan than in the VMAT and HT plans, with the highest bladder D2cc value being observed in the HT plan. However, no difference was observed in the rectum D2cc of the three plans. Other major advantages of the BRT plan over the VMAT and HT plans were the relatively lower body integral doses and femoral head doses as well as the fact that the integral doses were significantly lower in the BRT plan than in the VMAT and HT plans. This is the first dosimetric comparison of vaginal vault treatment for EC with BRT, VMAT, and HT plans. Our analyses showed the feasibility of stereotactic body radiotherapy technique as an alternative to HDR-BRT for postoperative management of EC patients.

177. Feasibility of SBRT-VMAT as an alternative to HDR brachytherapy for vaginal cuff. A dosimetric study

PurposeWe evaluate the role of stereotactic body radiotherapy (SBRT) using VMAT technique as an alternative to high-dose rate brachytherapy (HDR-BRT) in the treatment of vaginal cuff in postoperative endometrial cancer. MethodsCT scans of 5 patients were used in this study. The CTV was defined as the 0.5 cm tissue around the applicator (then subtracting the applicator). Total dose was 30 Gy delivered in 5 fractions. In HDR-BRT, dose was prescribed at a distance of 0.5 cm from the surface applicator. For VMAT diation, a PTV was obtained from CTV by an expansion of 3 mm. Two VMAT plans were generated using a full arc rotation. The first plan was optimized with an anatomy-based optimization module (AB_VMAT) using a 1 mm MLC beam margin to enhance dose fallout. The second plan was generated with a full-inverse planning module (FI_VMAT). Conformity (CI100, CI50), gradient (GI), homogeneity (HI) indexes and equivalent uniform dose (EUD) were calculated. A Kruskal-Wallis ANOVA was performed. ResultsVMAT plans provided targets coverage comparable with HDR (p < 0.05). Dose distributions were more heterogeneous with HDR: Dmean were 144.2% for CTV in HDR and 118.0 and 109.1% for PTV in AB_VMAT and FI_VMAT, respectively. The mean values of EUD for CTV were: HDR 40.9 Gy; AB_VMAT 39.0 Gy; FI_VMAT 33.3 Gy. GI indexes were 2.81, 3.37 and 4.15 for HDR, AB_VMAT and FI_VMAT, respectively. Dmean and maximal doses to 2 cc for rectum and bladder were lower in HDR-BRT plans compared to AB_VMAT and FI:VMAT (rectum Dmean: 39.8% vs 47.4% and 53.0%; bladder Dmean: 35.4% vs 40.4% and 46.1%; rectum D2cc: 104.8% vs 108.0% and 116.2%; bladder D2cc: 86.64% vs 94.0% and 100.0%). ConclusionsHDR-BRT provided superior dose distribution with respect to VMAT. AB_VMAT plans tend to better mimic the HDR dose distribution, providing a fast, safe and reasonable alternative.

22 A decision tool for interstitial needles implants in uterovaginal pulsed dose rate brachytherapy

Introduction Implants of interstitial needles (IN) in uterovaginal brachytherapy treatments has proved its efficiency in case of parametrial invasion [1] , [2] . The aim of the present study is to analyze patient anatomy and to determine cases where interstitial needles implants could help to cover the high risk volume. Methods Fifteen patient plans with interstitial needles were considered. On MRI or CT images post implantation, following dimensions where reported: the smallest distance between uterine probe and the nearest organ at risk in the anterior direction (frequently the bladder), and secondly the biggest lateral dimension between uterine probe and the edge of high risk CTV. The ratio of these two values is called r. PDR dose plans were calculated and optimized on Oncentra® TPS using the same dosimetric method by a single operator, with and without needles activation. CTV coverage (D90 of CTVHR and CTVIR) and organ at risk near-maximum doses (D2cc for bladder, rectum and sigmoid) were reported and compared. Results Doses comparison of CTV coverage showed that r = 2 is a threshold. Wilcoxon test for paired samples reveals that below this value, IN implant did not significantly improve CTV coverage. But for cervix uteri for which r is higher than 2, IN implant was a great help to increase CTV doses (D90 of CTVHR increases by an average of 16 Gy, and D90 of CTVIR by an average of 9,2 Gy – p = 0.00195), without significant variation of doses received by OARs (p > 0,2). Conclusions Interstitial needles implants can improve target volumes coverage when the high risk volume presents a r ratio higher than 2, with no change on organ at risk near-maximum doses.