American Brachytherapy Society Recommendations Research Articles

Interfraction variations in doses at OARs during three-dimensional high dose rate brachytherapy planning of cervix cancer.

The American Brachytherapy (BT) Society recommends that BT must be included as a component of the definitive radiation therapy for cervical carcinoma because recurrences and complications are decreased when BT is used in addition to external beam radiotherapy. The aim of this study is to quantify the interfraction dose variations (VARacts) during high dose rate (HDR) BT, the effect of variation in dose in terms of excess "unrecognized" dose to OAR and to conclude the reason of the variation in reference of applicator position/geometry versus deformation of the organ at risk (OAR) concerned. Total 30 patients of carcinoma cervix, biopsy proven, between June 2018 and May 2019, were taken for the study. All patients were treated with external beam radiation therapy to a dose of 50 Gy in 25 fractions over 5 weeks, followed by three fractions of HDR intracavitary brachytherapy (ICBT) (7.5 Gy to point A in each fraction) by two-dimensional (2D) X-ray-based planning. Before treatment in the first and last fraction of BT, computed tomography (CT) scan was done for every patient. Then, a 3D-based planning was performed with CT images on our HDR Plus software with image sequence option. VARact was calculated. Rigid image registration of consecutive fraction images was used for quantification of the hypothetical variation in dose (VARhypo) arising exclusively due to changes in applicator placement and geometry. The mean contoured rectal volumes for the first and third fractions were 41.49 cc and 44.72 cc, respectively, while the respective volumes for bladder were 9.33 cc and 9.35 cc cm. These differences were statistically insignificant (P value: 0.263 and 0.919 for rectum and bladder, respectively). The mean equivalent dose in 2 Gy fraction (EQD2) bladder D2cc was 5.68 Gy and 5.79 Gy in the first and third fraction ICBT, respectively. The mean EQD2 for the rectal D2cc was 11.63 Gy and 12.85 Gy in the first and third fraction ICBT, respectively. None of the patients had an actual cumulative EQD2 more than 90 Gy for bladder, but 36.66% of the patients had a rectal dose exceeding the tolerance (75 Gy). Regression plots showed that VARhypo alone could predict about 42.2% of the VARact in the rectum and 19.2% of the VARact in the bladder. Thus, the remaining variation was due to the organ deformation-related dose variations between the two fractions. There were no statistically significant variations in the volumes or doses of OAR between the two fractions. However, a significant proportion of patients may have a higher dose to the OAR in the third fraction in the absence of individualized planning. This increase is likely to be more detrimental where higher doses per fraction are used. Variations in OAR doses may be caused by organ deformation and/or changes in applicator placement/geometry.

Optimizing Toxicity and Local Control in Adjuvant Vaginal Cuff HDR brachytherapy: Stand vs. Suspender Immobilization and One vs. Two-centimeter Active Length Prescriptions

Vaginal cuff recurrence is common following hysterectomy for endometrial and cervical cancer. The American Brachytherapy Society recommends prescribing to an active length (AL) of 3-5 cm (AL) with vaginal cuff brachytherapy (VCB) following hysterectomy. Treatment toxicity is associated with length of vagina irradiation. The most common fractional and fixed length prescriptions in endometrial cancer are the proximal half of the vagina or 4 cm, respectively. The purpose of this study is to evaluate the local control and toxicity of VCB using AL prescriptions of 1 or 2 cm with a traditional stand or patient-mounted straps for immobilization. Between March 2005 and January 2019, 251 patients with gynecologic cancer were treated with high dose-rate VCB. AL was 1 (52%) or 2 (48%) cm prescribed to a depth of 0.25 (10%) or 0.5 cm (90%) using a traditional stand (47%) or custom in-house patient-mounted straps (53%) for immobilization. A majority of patients immobilized with straps were treated to an AL of 2 cm (90%). Mean follow-up was 39 months (range, 3-111 months). Forty-one percent of patients were stage IA; IB, 29%; II, 6%; III, 22%; IV, 2%. Pathology included: adenocarcinoma, 73%; papillary serous/clear cell carcinoma, 18%; and other, 9%. Associated grades included: I, 14%; II, 33%; and III, 42%. VCB was most commonly prescribed as a single modality to 21 Gy in 3 fractions (37%), with a mean BED2 of 32 Gy (9.3-61 Gy). Using a dose of 45-56.2 Gy, 52% of patients received external beam radiation (XRT). VCB boost was most commonly prescribed to 11 Gy in 2 fractions (70%), with a mean total BED2 to the vaginal cuff of 62 Gy (54-83 Gy). Vaginal cuff recurrence-free survival (VcRFS) at 5 years was 99% and 89% (p = .13) using AL prescriptions of 2 vs 1 cm, respectively. VcRFS at 5 years was 100% and 88% (p = .013) using strap vs stand immobilization, respectively. In the VCB only group: 15.5%, 11.8%, and 7.5% of patients experienced grade 1-2 vaginal, bladder, rectal toxicities, respectively. Grade 1-2 toxicities in the VCB only group were: 7.2%, 17%, and 8.5% at 1 cm AL compared to 22%, 4.1%, and 2% at 2 cm AL (each to vagina, bladder, and rectum, respectively). One patient treated to an AL of 2 cm had a grade 3 toxicity (rectal). In the XRT+VCB group: 22%, 36%, and 60% of patients experienced grade 1-2 vaginal, bladder, and rectal toxicities, respectively. Four patients had a grade 3 toxicity (1 bladder and 3 rectal). Limiting the AL prescription to 2 cm results in minimal toxicity and excellent local control. Though not significantly different, our results suggest exercising caution when considering a 1 cm AL. Patients immobilized with straps had improved 100% 5-year VcRFS. Prospective trials comparing immobilization techniques and prescription length are needed.

Adjuvant Vaginal Cuff HDR Brachytherapy Prescribed to an Active Length of Two Centimeters Using Suspender Immobilization: A Baylor Scott & White Experience

Following hysterectomy for endometrial and cervical cancer, recurrence is common in the vaginal cuff. The American Brachytherapy Society recommends prescribing to an active length (AL) of 3-5 cm (AL) with vaginal cuff brachytherapy (VCB) following hysterectomy (Gaffney D, et al. Brachytherapy 2012). The most common fixed and fractional length prescriptions in endometrial cancer are 4 cm or the proximal half of the vagina, respectively (Small W Jr, et al. Brachytherapy 2016). Length of vagina irradiation is associated with toxicity (Smeds AC et al. Int J Radiat Oncol BIol Phys 1990). The purpose of this study is to evaluate the efficacy in terms of local control and toxicity using 2 cm AL prescription during VCB following hysterectomy using patient mounted straps for immobilization. Between September 2015 and January 2019, 66 patients with endometrial (n=60) or cervical (n=6) cancer were treated with high dose-rate VCB to an AL of 2 cm prescribed to 0.5 cm depth using custom in-house patient-mounted straps for immobilization. Mean follow-up was 27 months (6-79 months). Twenty-eight percent of endometrial cancer patients were stage IA; IB, 33%; II, 13%; III, 22%; IV, 3%. Cervical cancer was mostly stage IB. Endometrial pathology included: adenocarcinoma, 57%; papillary serous/clear cell carcinoma, 28%, sarcoma, 15%. Associated grades included: I, 7%, II, 27%, and III, 67%. Cervical pathology was mostly squamous and grade III. The patients received different fractionation schedules and total doses, which were converted to BED2 using the L/Q model. VCB was typically prescribed as a single modality to 2100 cGy at 700 cGy per fraction (n=18) with a mean BED2 of 30 Gy (range, 30-31 Gy). Forty-one (68%) endometrial and 6 (100%) of cervical cancer patients received external beam to the pelvis (XRT) using a dose of 4500-5040 cGy. VCB boost was typically prescribed to 1100 cGy at 550 cGy per fraction (n=33) with a mean total BED2 to the vaginal cuff of 54 Gy (range, 54-69 Gy). There were no vaginal cuff failures. One patient experienced likely dropped metastasis at the vaginal introitus 10 months after completion of brachytherapy. Vaginal cuff recurrence-free survival (VcRFS) and vaginal recurrence-free survival (VRFS) at 3 years were 100% and 98%, respectively. With regards to vaginal toxicity, in the XRT+VCB group: one patient (2%) developed acute grade ≥2 toxicity and two patients (4%) developed chronic grade 1 toxicity. In the VCB only group, no patients experienced grade ≥2 toxicities. Three (16%) and 1 (5%) patients experienced acute and chronic grade 1 toxicity, respectively. Limiting the AL to 2 cm while using custom in-house patient mounted straps for immobilization results in minimal toxicity and excellent local control.

Analysis in organs at risk for gynecological radiotherapy by High Dose Rate Brachytherapy using Manchester point A, ICRU 38 Report and American Braquitherapy Society recomendation

The gynecological treatment with High Dose Rate (HDR) Brachytherapy imply deliver dose to the tumor and spare the dose in organs at risk. In this work we apply the recommendations for prescribing dose given by the International Commission of Radiation Units (ICRU) reports 38, 89 and the American Brachytherapy Society (ABS). With both schemes of optimization, recommendation of ICRU 38 or ABS with vaginal point from ICRU 89. Were analyze the dose received by the organs at risk, in this case rectum and bladder and also the irradiated volume for patients that receive HDR brachytherapy treatment. An afterloading technique is applying with a Eckert & Ziegler MultiSource ® equipment using a Co-60 source, 30 patients with 4 applications with cervical cancer are planning with HDR brachytherapy. This work analyze 120 single applications with orthogonal images using the treatment planning system (TPS) HDRplus version 3.0.4 through “Auto dwell time determination” optimization method, using the recommendation for optimization dose from the ABS and vaginal point from ICRU 89 . The volume of the isodose curve of prescription is 15% less using ABS recommendation than ICRU 38. The bladder dose is 11% and rectum dose is 21% less using ABS recommendation than ICRU 38. The analysis of dose prescription using ICRU 38 and ABS recommendations in the patients analyzed shows less irradiated volume at the dose prescribed and also less mean dose in rectum and bladder of applications using ABS in contrast with ICRU 38 recommendations.

High-Dose-Rate Orthogonal Intracavitary Brachytherapy with 9Gy/Fraction in Locally Advanced Cervical Cancer: Is it Feasible??

Though high dose rate (HDR) intracavitary brachytherapy (ICBT) is now an integral part in the treatment of cervical cancer, the quest for optimum dose and fractionation schedule is still ongoing. While the American Brachytherapy Society recommends individual fraction size of <7.5Gy, there are few studies where the authors obtained similar results with higher dose per fraction. To compare and analyse two high-dose-rate intracavitary brachytherapy schedules-7Gy per fraction for three fractions with 9Gy per fraction for two fractions. This is a prospective institutional study in Southern India carried on from 1 June 2012 to 31 March 2013. In this period, 124 patients of cervical cancer satisfying our inclusion criteria were treated with concurrent chemo-radiation, following which patients were randomized to one of the treatment arms, with 62 patients in each arm. The ICBT dose in Control Arm A was 7Gy per fraction in three fractions, 1week apart. While in Study Arm B, the ICBT dose was 9Gy per fraction in two fractions, again 1week apart. One patient in Arm A and three patients in Arm B discontinued the treatment even after repeated counselling and hence were excluded from the study analysis. The median follow-up period in the study was 25.2months. In the Control Arm A, the 2-year actuarial local control rate, disease-free survival and overall survival were 88.5, 86.9 and 92.6%, respectively, while in the Study Arm B, the 2-year actuarial local control rate, disease-free survival and overall survival were 91.5, 88.1 and 86.4%, respectively. In our experience, HDR brachytherapy with 9Gy per fraction in two fractions is an effective dose fractionation when compared to 7Gy per fraction in three fractions.

Vaginal brachytherapy for postoperative endometrial cancer: 2014 Survey of the American Brachytherapy Society.

Report current practice patterns for postoperative endometrial cancer emphasizing vaginal brachytherapy (VBT). A 38-item survey was e-mailed to 1,598 American Brachytherapy Society (ABS) members and 4,329 US radiation oncologists in 2014 totaling 5,710 recipients. Responses of practitioners who had delivered VBT in the previous 12months were included in the analysis. Responses were tabulated to determine relative frequency distributions. χ(2) analysis was used to compare current results with those from the 2003 ABS survey. A total of 331 respondents initiated the VBT survey, of whom 289 (87.3%) administered VBT in the prior 12months. Lymph node dissection and number of nodes removed influenced treatment decisions for 90.5% and 69.8%, respectively. High-dose-rate was used by 96.2%. The most common vaginal length treated was 4cm (31.0%). Three-dimensional planning was used by 83.2% with 73.4% of those for the first fraction only. Doses to normal tissues were reported by 79.8%. About half optimized to the location of dose specification and/or normal tissues. As monotherapy, the most common prescriptions were 7Gy for three fractions to 0.5-cm depth and 6Gy for five fractions to the surface. As a boost, the most common prescriptions were 5Gy for three fractions to 0.5-cm depth and 6Gy for three fractions to the vaginal surface. Optimization points were placed at the apex and lateral vagina by 73.1%. Secondary quality assurance checks were performed by 98.9%. VBT is a common adjuvant therapy for endometrial cancer patients, most commonly with HDR. Fractionation and planning processes are variable but generally align with ABS recommendations.

American Brachytherapy Society consensus guidelines for thoracic brachytherapy for lung cancer.

To update brachytherapy recommendations for pretreatment evaluation, treatment, and dosimetric issues for thoracic brachytherapy for lung cancer. Members of the American Brachytherapy Society with expertise in thoracic brachytherapy updated recommendations for thoracic brachytherapy based on literature review and clinical experience. The American Brachytherapy Society consensus guidelines recommend the use of endobronchial brachytherapy for disease palliation in patients with central obstructing lesions, particularly in patients who have previously received external beam radiotherapy. The use of interstitial implants after incomplete resection may improve outcomes and provide enhanced palliation. Early reports support the use of CT-guided intratumoral volume implants within clinical studies. The use of brachytherapy routinely after sublobar resection is not generally recommended, unless within the confines of a clinical trial or a registry. American Brachytherapy Society recommendations for thoracic brachytherapy are provided. Practitioners are encouraged to follow these guidelines and to develop further clinical trials to examine this treatment modality to increase the evidence base for its use.

High Dose Rate Brachytherapy in Two 9 Gy Fractions in the Treatment of Locally Advanced Cervical Cancer - a South Indian Institutional Experience.

Although 3D image based brachytherapy is currently the standard of treatment in cervical cancer, most of the centres in developing countries still practice orthogonal intracavitary brachytherapy due to financial constraints. The quest for optimum dose and fractionation schedule in high dose rate (HDR) intracavitary brachytherapy (ICBT) is still ongoing. While the American Brachytherapy Society recommends four to eight fractions of each less than 7.5 Gy, there are some studies demonstrating similar efficacy and comparable toxicity with higher doses per fraction. To assess the treatment efficacy and late complications of HDR ICBT with 9 Gy per fraction in two fractions. This is a prospective institutional study in Southern India carried on from 1st June 2012 to 31st July 2014. In this period, 76 patients of cervical cancer satisfying our inclusion criteria were treated with concurrent chemo-radiation following ICBT with 9 Gy per fraction in two fractions, five to seven days apart. The median follow-up period in the study was 24 months (range 10.6 - 31.2 months). The 2 year actuarial local control rate, disease-free survival and overall survival were 88.1%, 84.2% and 81.8% respectively. Although 38.2% patients suffered from late toxicity, only 3 patients had grade III late toxicity. In our experience, HDR brachytherapy with 9 Gy per fraction in two fractions is an effective dose fractionation for the treatment of cervical cancer with acceptable toxicity.

Nationwide Japanese Prostate Cancer Outcome Study of Permanent Iodine-125 Seed Implantation (J-POPS)

To evaluate the safety and efficacy of brachytherapy with permanent iodine-125 seed implantation (PI) for prostate cancer. The nationwide Japanese Prostate Cancer Outcome Study of Permanent Iodine-125 Seed Implantation (J-POPS) has continued since July 2005. This manuscript presents the rationale, J-POPS study design, and the characteristics of initial participants enrolled in this study from July 2005 to June 2007. All participants were treated with PI in accordance with the American Brachytherapy Society recommendations. The primary outcome measure was biochemical progression-free survival. Progression-free survival, overall survival, cause-specific survival, longitudinal changes in health-related quality of life, disease-specific quality of life, the International Prostate Symptom Score, and the incidence of adverse events were also investigated as secondary outcome measurements. Overall, 6,927 patients were enrolled by the end of 2010, that is approximately 40 % of all cases treated around the country. During the first 2 years, 2,354 participants were enrolled and 2,339 were actually treated with PI. The age range of participants was 45 to 89 years (median 69 years) and their risk classifications were 1,037 (44.3 %) at low risk, 1,126 (48.1 %) at intermediate risk, and 134 (5.7 %) at high risk, in addition to 16 participants whose classification was unknown. Of all patients, 76.6 % were treated with PI without external beam radiation therapy and 49.3 % received neoadjuvant hormone therapy. The J-POPS, a nationwide prospective cohort study that enrolled approximately 40 % of all PI cases in Japan, will provide highly reliable evidence, including outcomes and quality of life, after long-term follow-up.

Dose estimation for different skin models in interstitial breast brachytherapy.

PurposeSkin is a major organ at risk in breast-conserving therapy (BCT). The American Brachytherapy Society (ABS) recommendations require monitoring of maximum dose received, however, there is no unambiguous way of skin contouring provided. The purpose of this study was to compare the doses received by the skin in different models.Material and methodsStandard treatment plans of 20 patients who underwent interstitial breast brachytherapy were analyzed. Every patient had a new treatment plan prepared according to Paris system and had skin contoured in three different ways. The first model, Skin 2 mm, corresponds to the dermatological breast skin thickness and is reaching 2 mm into an external patient contour. It was rejected in a further analysis, because of distinct discontinuities in contouring. The second model, Skin 4 mm, replaced Skin 2 mm, and is reaching 2 mm inside and 2 mm outside of the External contour. The third model, Skin EXT, is created on the External contour and it expands 4 mm outside. Doses received by the most exposed 0.1 cc, 1 cc, 2 cc, and the maximum doses for Skin 4 mm and Skin EXT were compared.ResultsMean, median, maximum, and standard deviation of percentage dose difference between Skin EXT and Skin 4 mm for the most exposed 0.1 cc (D0.1cc) of skin were 18.01%, 17.20%, 27.84%, and 4.01%, respectively. All differences were statistically significant (p < 0.05).ConclusionsMonitoring of doses received by skin is necessary to avoid complications and obtain a satisfactory cosmetic effect. It is difficult to assess the compatibility of treatment plans with recommendations, while there is no unambiguous way of skin contouring. Especially, if a mean difference of doses between two models of skin contouring is 18% for the most exposed 0.1 cc and can reach almost 28% in some cases. Differences of this magnitude can result in skin complications during BCT.

SU-E-T-517: Characterization of Relative Doses and Source Strengths for Various Plaque Sizes and Tumor Dimensions in the Treatment of Uveal Melanoma.

To characterize the relative doses and source strengths for various eye plaque sizes and tumor dimensions in the treatment of uveal melanoma. Several tumors with basal diameters ranging from 6-16mm and apical height of 5-10mm were planned using the Pinnacle3 treatment planning system following the American Brachytherapy Society's recommendations. The data is based on 5-day implant to deliver 85Gy with a dose rate of 70.9cGy/hr. Choice of plaque size is based on a 2-3 mm margin on either side of the tumor. Doses to the fixed locations: sclera, center of the eye and opposite sclera were obtained. From our results we see larger source strengths needed for smaller plaques due to smaller number of sources used. The exception is with 14mm and 16mm plaques containing the same number of sources where the 16mm plaque has slightly higher source strengths. For both the inner and outer sclera, the relative dose increases with increasing height. For a 12mm plaque, the relative dose of the outer sclera increases from 4-10 times that of the Rx dose at the apex of the tumor. For a 20mm eye plaque, the relative dose of the outer sclera increases from 2-5 times that of the prescription dose at the apex of the tumor. As apical height increases, the relative dose at the center of the eye increases to about 75% of the Rx dose at 10cm depth for all plaque sizes. At the inner sclera surface opposite the center of the tumor base the relative dose is 20-22% of the Rx dose for all plaque sizes. The data provided will be a helpful tool in evaluating and predicting complications in the retina and sclera based on the tumor dimensions and selected plaque size.

American Brachytherapy Society consensus guidelines for adjuvant vaginal cuff brachytherapy after hysterectomy

To develop recommendations for the use of adjuvant vaginal cuff brachytherapy after hysterectomy and update previous American Brachytherapy Society (ABS) guidelines. A panel of members of the ABS performed a literature review, supplemented their clinical experience, and formulated recommendations for adjuvant vaginal cuff brachytherapy. The ABS endorses the National Comprehensive Cancer Network guidelines for indications for radiation therapy for patients with endometrial cancer and cervical cancer and the guidelines on quality assurance of the American Association on Physicists in Medicine. The ABS made specific recommendations for applicator selection, insertion techniques, target volume definition, dose fractionation, and specifications for postoperative adjuvant vaginal cuff therapy. The ABS recommends that applicator selection should be based on patient anatomy, target volume geometry, and physician judgment. The dose prescription point should be clearly specified. Suggested doses were tabulated for treatment with brachytherapy alone, and in combination with external beam radiation therapy, when applicable. A properly fitted brachytherapy applicator should be selected that conforms to the vaginal apex and achieves mucosal contact with optimal tumor and normal tissue dosimetry. Dose prescription points may be individually selected but doses should be reported at the vaginal surface and at 0.5-cm depth. Recommendations are made for adjuvant vaginal cuff brachytherapy. Practitioners and cooperative groups are encouraged to use these recommendations to formulate their treatment and dose reporting policies. These recommendations will permit meaningful comparisons of reports from different institutions and lead to better and more appropriate use of vaginal brachytherapy.

Factors Influencing Urinary Symptoms 10 Years After Permanent Prostate Seed Implantation

We investigated the factors that influenced urinary symptoms in the first 10 years after prostate brachytherapy. A total of 1,932 men were treated with prostate brachytherapy alone or with external beam irradiation and followed a mean of 6.8 years. The influence of pretreatment American Urological Association symptom score (7 or less, 8 to 19, 20 or greater), external beam radiotherapy, (125)I or (103)Pd, biological effective dose, age, prostate size and hormone therapy on the change in American Urological Association symptom score (11,491) was compared. The mean change from initial score (7.4) was 11.4, 5.5, 3.3, 2.7, 1.5, 1.2, 1, 1, 1, 1, 1.3 and 1.4 points at 3, 6 months and 1 to 10 years, respectively (p <0.001). Factors that resulted in a greater increase in urinary symptoms at year 1 were low pretreatment score (p <0.001), no hormonal therapy (p <0.001), younger age (p = 0.046) and higher biological effective dose (p = 0.025). At 10 years patients with an initial score of 20 or greater had an average decrease of 11 points compared to a decrease of 0.9 for an initial score of 8 to 19 and an increase of 2.7 for an initial score of 7 or less (p <0.001). On linear regression the scores at 1 year were influenced by initial score (p <0.001), biological effective dose (p = 0.022), prostate size (p <0.001) and hormonal therapy (p = 0.009). At 10 years only the pretreatment score remained significant (p <0.001). There is minimal change in mean American Urological Association symptom score (1.4 points) 10 years after prostate brachytherapy. Patients presenting with high initial scores have the greatest improvement from baseline. Biological effective dose, external beam radiotherapy, hormonal therapy, isotope, patient age and prostate size do not appear to influence long-term urinary symptoms.

Optimization of high–dose-rate intracavitary brachytherapy schedule in the treatment of carcinoma of the cervix

Purpose At our institute, we use high–dose-rate (HDR) intracavitary brachytherapy (ICBT) schedule of 9 Gy per fraction for two fractions after external beam radiotherapy (EBRT) in patients with advanced carcinoma of the cervix. But American Brachytherapy Society recommends that individual fraction size should be less than 7 Gy per fraction in such patients. We present the results of comparison of our institution standard schedule with biologically equivalent dose of 6.8 Gy per fraction for three fractions in terms of local control, disease-free survival, and late toxicity. Methods and Materials Between October 2003 and August 2007, 104 patients with carcinoma of the uterine cervix (Stages IIB and IIIB) were treated with EBRT and HDR ICBT. After EBRT, patients were randomized to one of the treatment arms. ICBT dose in Control Arm A ( n = 52) was 9 Gy per fraction in two fractions, 1 week apart, and in Study Arm B ( n = 52), it was 6.8 Gy per fraction in 3 fractions, 1 week apart. Results The median followup was 31.48 months. The 3-year actuarial local control was 81.35% in Arm A and 65.18% in Arm B ( p = 0.0423), and the 3-year actuarial disease-free survival was 64.97% in Arm A and 49.47% in Arm B ( p = 0.0393). The 3-year actuarial risk of developing any Grade 3 or worse late toxicity was 7.47% in Arm A and 3.57% in Arm B ( p = 0.2907). Conclusion In our setup, HDR brachytherapy at 9 Gy per fraction in two fractions is safe and effective with good local control, survival, and manageable normal tissue toxicity.

Variation of Rectal, Bladder, Vaginal, and Parametrial Doses using the American Brachytherapy Society HDR Optimization Guidelines of Intracavitary Brachytherapy for Cervical Cancer: A Summary of the Most Possible Clinical Scenarios

Purpose: HDR brachytherapy for cervical cancer is gaining popularity. Dose prescription has evolved from the milligram Radium hour system to 3-D image based treatment-planning passing through ICRU point “A” in LDR and American Brachytherapy Society (ABS) point “H” in HDR. The ABS recommendations are still widely adopted in HDR planning since the clinical outcomes of GEC-ESTRO guidelines are still in the maturation phase. The purpose of this study is to evaluate the variation in rectal, bladder, vaginal,and parametrial doses using ABS guidelines in various case scenarios using different tandem lengths, tandem angles, and ovoid sizes. Materials and Methods: Seven hundred cGy was prescribed to point H, and was optimized using current ABS guidelines. Varian Eclipse software was used in this project. We performed several simulations on a model CT scan of a previously treated patient. We used tandem lengths of 4, 6 and 8 cm; angle of the tandem to the central axis of the patient of 0, 15 and, 30 degrees; and mini (1.6 cm), small (2 cm), medium (2.5 cm) and large (3 cm) ovoid sizes. We performed DVH analysis and recorded D0.1cc, D1 cc, D 2 cc each for the rectum, sigmoid, and bladder. In addition we reported point doses of the bladder, rectum, bilateral vaginal points, and bilateral point B. Results: We performed 36 simulations utilizing the various above mentioned criteria. Our reference case used a 6cm tandem with an angle of 0 degree and medium ovoids (6.0, medium). Doses recorded were as follows: vagina, 1224 cGy; point B, 251 cGy; bladder, 506 cGy and rectum, 493 cGy. The D2cc of the rectum, sigmoid, and bladder were 370 cGy, 265 cGy, and 405 cGy, respectively. The highest (H) and lowest (L) doses of each organ/point with the corresponding parameters is listed in the table below: Table 1OrganDose in cGy (% of Point H Dose)Tandem Length (cm)Tandem Angle (Degree)ovoid sizeVagina H1500 (214%)40miniVagina L1081 (154%)830largePoint B H371 (53%)830largePoint B L151 (22%)40miniBladder H637 (91%)430largeBladder L393 (56%)40miniRectum H597 (85%)60largeRectum L323 (46%)40miniBladder D2cc H560 (80%)430largeBladder D2cc L315 (45%)40miniRectum D2cc H470 (67%)430largeRectum D2cc L245 (35%)40miniSigmoid D2cc H285 (41%)80mediumSigmoid D2cc L180 (26%)430mini Open table in a new tab Conclusions: When using the ABS guidelines, the tandem length is directly related to point B and sigmoid doses. The ovoid size is directly proportional to rectal and bladder doses while inversely proportional to vaginal dose. The tandem angle is directly related to ipsilateral point B and ipsilateral vaginal doses. These numbers are for reference only. Caution should be adopted when using less than optimal parameters, as it would reflect into higher doses to critical structure that may lead to serious complications.

Factors Predicting Prostatic Biopsy Gleason Sum Under Grading

We determined clinical factors affecting the under grading of biopsy Gleason sum compared with prostatectomy pathology and developed a model predicting the probability of under grading. We analyzed a cohort of 1,701 patients treated for prostate cancer at our institution between 1988 and 2007 with complete biopsy and pathological data available. Patients with a biopsy Gleason sum of 7 or less were included in our analysis. Cases were categorized as under graded or not under graded by comparing biopsy and radical prostatectomy Gleason sums. Logistic regression was used to determine the predictors of under grading based on clinical variables (race, age at diagnosis, body mass index, prostate weight, diagnostic prostate specific antigen, biopsy positive-to-total core ratio, maximal cancer percent in positive cores and time from diagnosis to surgery). A nomogram was developed to calculate the probability of under grading. Results were validated using bootstrapping. Under grading occurred in 46.6% of our cohort. Significant variables predicting under grading were age at diagnosis, biopsy Gleason sum, diagnostic prostate specific antigen, prostate weight, biopsy positive-to-total core ratio and maximal percent of cancer in cores (p <0.05). Nomogram predictive accuracy was 72.4%. The risk of Gleason sum under grading can be predicted to a satisfactory level using our nomogram. Predicting under grading would improve patient consulting and identify those who should consider repeat biopsy, ultimately enhancing the accuracy of prostate cancer diagnosis.

Point A or Point H in Prescribing High-Dose-Rate (HDR) Intracavitary Brachytherapy for Cervical Carcinoma?

The Manchester system is the most common system used in intracavitary brachytherapy for cervical carcinoma. Although some variations exist, it defines typically point A dose as the dose at 2 cm above the external cervical os (flange) and 2 cm lateral to midline (tandem) along the plane of the tandem. Because point A occurs in a high-gradient region of the isodose distribution, minor differences in application may lead to major differences in dose received. Therefore, the American Brachytherapy Society (ABS) recommends prescribing the dose to a new point H such that it falls sufficiently superior to the ovoids where the isodose distribution runs parallel to the tandem (1).

American Brachytherapy Society recommends no change for prostate permanent implant dose prescriptions using iodine-125 or palladium-103

Purpose In 2004, the American Association of Physicists in Medicine (AAPM) issued a report outlining recommended 125I and 103Pd datasets for consistency in calculating brachytherapy dose distributions. In 2005, to aid evaluating the clinical impact of implementing these datasets, the AAPM assessed the historical dependence of how prescribed doses differed from administered doses for 125I and 103Pd for permanent implantation of the prostate. Consequently, the American Brachytherapy Society (ABS) considered the nature of these changes towards issuing recommended dose prescriptions for 125I and 103Pd interstitial brachytherapy implants for monotherapy and standard boosts. Methods and materials An investigation was performed of the 2005 AAPM analysis to determine changes in administered dose while affixing prescribed dose using 2004 AAPM 125I and 103Pd brachytherapy dosimetry datasets for prostate implants. For 125I and 103Pd, administered dose would change by +1.4% and +4.2%, respectively. The biological and societal impact of changing prescribed dose was considered. Results Based on the need for clinical constancy and in recognition of overall uncertainties, the ABS recommends immediate implementation of the 2004 AAPM consensus brachytherapy dosimetry datasets and no changes to 125I and 103Pd dose prescriptions at this time. Conclusions Radiation oncologists should continue to prescribe monotherapy doses of 145 Gy and 125 Gy for 125I and 103Pd, respectively, and standard boost doses of 100-110 Gy and 90-100 Gy for 125I and 103Pd, respectively.

Prostate Cancers Scored as Gleason 6 on Prostate Biopsy are Frequently Gleason 7 Tumors at Radical Prostatectomy: Implication on Outcome

Differentiation between Gleason score 6 and 7 in prostate biopsy is important for treatment decision making. Nevertheless, under grading errors compared with the actual pathological grade at radical prostatectomy are common. We compared the characteristics and outcomes of tumors that were scored 6 on prostate biopsy but were 7 on subsequent radical prostatectomy pathological evaluation to those in tumors with a consistent rating of Gleason score 6 or 7 at biopsy and surgery. We performed a retrospective database analysis from our referral center (1989 to 2004). We compared pre-prostatectomy characteristics, radical prostatectomy pathological features and the post-radical prostatectomy prostate specific antigen failure rate, defined as any 2 consecutive detectable prostate specific antigen measurements, in 3 subgroups of patients, including 156 with matched Gleason score 6 in the prostate biopsy and radical prostatectomy, 205 with upgraded Gleason score 6/7, that is prostate biopsy Gleason score 6 and radical prostatectomy Gleason score 7, and 412 with matched Gleason score 7 in the prostate biopsy and radical prostatectomy. Radical prostatectomy Gleason score matched the prostate biopsy score in 38.2% of biopsy Gleason score 6 and 81.4% of biopsy Gleason score 7 cases. Higher prostate specific antigen was associated and an increased percent of cancer in the prostate biopsy was predictive of discordance between the prostate biopsy and radical prostatectomy Gleason scores (p <0.001). Margin (p = 0.0075) or seminal vesicle involvement (p = 0.0002), cancer volume (p <0.001) and the prostate specific antigen failures rate (p = 0.014) were significantly higher in under graded Gleason score 7 cancer compared to those in matched Gleason score 6 cases. However, they were comparable to those with a matched Gleason score 7 tumor grade (p = 0.66). Almost half of tumors graded Gleason score 6 at biopsy are Gleason score 7 at surgery. Upgraded Gleason score 6 to 7 tumors have outcomes similar to those of genuine Gleason score 7 cancer. For prostate biopsy Gleason score 6 tumors clinicians should consider the overall likelihood of tumor upgrading as well as specific patient characteristics, such as prostate specific antigen and the percent of tumor in the prostate biopsy, when contemplating treatments that are optimized for low grade tumors, including watchful waiting or brachytherapy.

SU-FF-T-50: Reduction of Computed Tomography Metal Artifacts Due to I-125 Seeds for Post Implant Analysis in Prostate Permanent Brachytherapy

Purpose: Postimplant analysis in I‐125 permanent brachytherapy for prostate cancer plays important role in improving the techniques of implant. Although American Brachytherapy Society recommends CT based postimplant analysis, the identification of prostate bundle is quite difficult. In addition, metal artifacts from the I‐125 seeds implanted make it more difficult to identify the prostate. Thus accuracy of the dosimetric parameters associated with volume of prostate such as D90 and V100 may be unclear. The purpose of this study is to mitigate CT metal artifacts due to I‐125 seeds to provide more accurate postimplant analysis. Method and Materials: The prostate phantom that was implanted 3 to 10 seeds per a plane was scanned using 16‐detector raw CT. The sinogram was modified by our algorithm that is similar to projection‐interpolation method to CTimages containing artifacts from I‐125 seeds. The regions of projection data existing I‐125 seeds were identified by observing differences of X‐ray intensity between the phantom and the seeds. Then the regions were interpolated to remove the metal artifacts. The new images were reconstructed with the corrected sinogram. We compared these with the CTimages that are corrected by commercially available metal artifact reduction method. Results: The metal artifacts caused by a small number of I‐125 seeds were completely eliminated by our correcting method. On the other hand, the magnitude of the artifact with the commercially available method was insufficient. With regard to many seeds in the same plane, the metal artifact was mitigated by our method although the contrast of images was degraded. Conclusion: Our method would mitigate metal artifacts caused by I‐125 seeds and be helpful to identify prostate. Although some problems have still remained to improve, our approaches would be adapted to clinical field.