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Does Anesthesia during Cervical Cancer Brachytherapy Improve Implant Quality?
I. J. Radiation Oncology d Biology d Physics
S408
Volume 78, Number 3, Supplement, 2010
Materials/Methods: Between 2000 and 2009, 39 patients with cervical cancer aged $ 75 years old received radiotherapy as definitive (34 patients) or postoperative adjuvant (5 patients) treatment at our institution. Median age was 78 years old (Range: 75 89). Thirty-seven patients had squamous cell carcinoma and 2 had adenocarcinoma. Twenty-four patients had FIGO I/II stage, 15 had III/IVA stage. Among 34 patients treated with definitive radiotherapy, 30 received external beam radiotherapy (EBRT) combined with intracavitary brachytherapy (ICBT), 3 received EBRT alone and 1 received ICBT alone. Among 5 patients treated with postoperative adjuvant radiotherapy, 3 received EBRT alone and 2 received EBRT combined with ICBT. Median total doses of EBRT and ICBT were 50.4 Gy (Range: 0 - 61.2) and 18.0 Gy (Range: 4.5 - 31.0), respectively. Three patients treated with definitive radiotherapy received concurrent chemotherapy using weekly cisplatin. Results: Median follow-up period was 18 months (Range: 1 - 85). Only 1 patient could not complete the treatment. Seven patients experienced recurrence (local: 4, para-aortic lymph node: 1, distant: 1, tumor marker elevation: 1). Nine patients died during the follow-up period. Five patients died due to the primary disease and 4 due to other causes. The 5-year overall and disease-specific survival (OS and DSS) rates of all patients were 55% and 78%, respectively. The 5-year OS rates in FIGOI/ II and III/IVA stage were 65% and 40%, respectively. The 5-year DSS rates in FIGO I/II and III/IVA stage were 88% and 66%, respectively. Grade 3 or greater late radiation toxicity occurred only in 2 patients (5%). One experienced hemorrhagic cystitis (Grade 3) after definitive radiotherapy, the other experienced adhesive intestinal obstruction (Grade 3) after postoperative adjuvant chemotherapy. Conclusions: Radiotherapy for elderly patients with cervical cancer was well tolerable and the survival outcomes were compatible with other previous reports. Our results indicate that radiotherapy is an useful modality for elderly patients with cervical cancer aged $ 75 years old and the importance of radiotherapy will be greater in the aging society. Author Disclosure: K. Yoshida, None; H. Nishimura, None; D. Miyawaki, None; T. Kawabe, None; Y. Okamoto, None; K. Nakabayashi, None; S. Yoshida, None; R. Sasaki, None; K. Sugimura, None.
2458
3D Image-based Customized Treatment Planning versus Standard Plans for Cervix Cancer HDR Brachytherapy
P. Mobit, M. C. Baird, M. R. Kanakamedala, W. F. Mourad, S. Vijayakumar, C. C. Yang University Of Mississippi Medical Center, Department of Radiation Oncology, Jackson, MS Purpose/Objective(s): To investigate the advantages of volumetric treatment planning in HDR brachytherapy for cervical carcinoma compared to standardized loading and 2D planning techniques. Materials/Methods: Our institution uses volume based 3D planning for each tandem and ovoid (T&O) insertion of HDR brachytherapy in the treatment of advanced cervical carcinoma. We attempt to define the benefits of this approach. We re-planned 70 CT based plans on 15 patients (treated in our facility between February, 2009-February, 2010) using a commonly used standard HDR loading of T&O. All patients received 4 fractions of 6.5 Gy or 5 fractions of 5.5 Gy to point H or A. The following organs at risk (OARs) were contoured: rectum, bladder, sigmoid and small bowel. Our customized planning requires adjustment of source dwell times and positions to keep doses to the OARs below 80% of prescription dose. The standardized HDR planning bases the loading on the length of the tandem. The dwell time for each tandem source position is the same. The dwell time multipliers for the ovoids were 0.33, 0.665 and 1.0 proportional to the 2 cm, 4 cm and 6 cm tandem length respectively. The dose to 2cc (D2cc) to OARs were analyzed, in addition to the volume covered by the prescription isodose and the maximum width and length of the pear shaped dose distribution for both the customized plan and the standardized plan. Results: In general, the dose to 2cc (D2cc) for the rectum and sigmoid was much lower with the customized planning technique. This dose was up to 60% lower for the customized plans for a 6.0 cm tandem. These differences in the D2cc for the rectum and sigmoid reduced when a 4 cm length tandem was used. In most cases, the D2cc of the bladder was lower for the standard plans compared to the customized ones. There was marked change in the D2cc for all OARs from one HDR session to the next with both the standard and customized plans. The pear shape dose distribution maximum width and length is smaller for the customized plans compared to the standard plan (was up to 1 cm) while the volume encompassed by the prescription isodose surface was up to 15% smaller than that obtained from the standard plan. Conclusions: Using customized plans for HDR T&O leads to reduced doses to the rectum, small bowels and sigmoid but the dose to the bladder was almost always higher. The dose to the small bowel could be up to 30% higher than the dose to point H or A in standard plans indicating that customized plans are superior to the standard ones for T&O for this group of patients. It is recommended to use CT/MRI images for any customized based HDR planning as the smaller treatment volume of the customized treatment plan makes geometric miss of the tumor volume more likely. Author Disclosure: P. Mobit, None; M.C. Baird, None; M.R. Kanakamedala, None; W.F. Mourad, None; S. Vijayakumar, None; C.C. Yang, None.
2459
Does Anesthesia during Cervical Cancer Brachytherapy Improve Implant Quality? 1
C. J. Anker , K. O’Donnell2, K. M. Boucher1, D. K. Gaffney1 1
University of Utah Huntsman Cancer Institute, Salt Lake City, UT, 2Oregon Health & Science University, Portland, OR
Purpose/Objective(s): To evaluate the relationship between anesthesia use and dose to objects-at-risk (OAR) in patients undergoing brachytherapy for cervix cancer. In addition, we sought to quantify the effects of high dose rate (HDR) brachytherapy technique and patient characteristics on dose distribution to OARs. Materials/Methods: From 1998 to 2008, 65 cervical cancer patients with FIGO stages IB1-IVA disease were identified receiving definitive external beam radiation and HDR brachytherapy with tandem and ovoid applicators. The 31 patients who had full dosimetric data were included in this analysis. Doses were recorded at point A, the ICRU-38 rectal point, ICRU-38 bladder point, and the vaginal surface. Generalized estimating equations were used to determine the significance of changes in OAR to point A dose ratios with differences in brachytherapy technique or patient characteristics.
Proceedings of the 52nd Annual ASTRO Meeting Results: Patients underwent a median of 5 brachytherapy procedures (range, 3-6), with a total of 179 procedures for 31 patients. For all brachytherapy treatments, the median ratios between the doses at the rectal, bladder, and vaginal surface reference points to those at point A were 0.48, 0.55, and 1.07, respectively. In general, decreased OAR dose was associated with increased ovoid size, increased tandem length, and earlier implant number. Anesthesia usage was not correlated with any of these favorable procedure characteristics, and its use was actually associated with increased bladder and vaginal surface dose. As expected, increased tandem curvature significantly increased the bladder dose and decreased rectal dose. As advanced age was associated with decreased ovoid size and increased tandem curvature, bladder dose increased as well. Higher FIGO stage was associated with decreased ovoid size and curvature, with resulting increased rectal dose. Conclusions: This study allowed identification of patient and procedure characteristics influencing OAR dosing. Of particular importance, the use of anesthesia did not correlate with decreased OAR dose in our series. Although the advent of 3D image-guided brachytherapy will bring new advances in treatment optimization, the actual technique involved at the time of the brachytherapy implant procedure will remain important. Author Disclosure: C.J. Anker, None; K. O’Donnell, None; K.M. Boucher, None; D.K. Gaffney, None.
2460
Initial Experience with Alatus Vaginal Balloon Packing (VBP) Compared to Standard Vaginal Gauze Packing (SGP) for Tandem and Ovoid Brachytherapy Treatment of Carcinoma of the Cervix
I. M. Ahmed, A. S. Saini, D. Hunt, W. Skinner, S. E. Finkelstein, M. C. Biagioli Moffitt Cancer Center, Tampa, FL Background: Brachytherapy in combination with external beam radiotherapy is standard treatment for locally advanced carcinoma of the cervix. Use of intracavitary implants requires appropriate vaginal packing to displace the rectum and bladder away from the radiation sources to minimize side-effects and complications. Typically, this is done via gauze packing, rectal retractor, and/or Foley balloon. Recently FDA approved Alatus VBP is an alternative form of vaginal packing for intracavitary brachytherapy. Purpose/Objective(s): We report initial experience with vaginal balloon packing (VBP) compared with standard gauze packing (SGP). Materials/Methods: Four patients undergoing fractionated HDR brachytherapy underwent alternating vaginal packing with either standard gauze packing (SGP) or with Alatus VBP. Brachytherapy was performed in 5 fractions, 600 cGy/ fraction, using a Royal Marsden applicator. Patients undergoing VBP, two balloons were used, one positioned anterior and second posterior to the ovoids and filled with normal saline. Brachytherapy planning was performed using an MRI for HRCTV and OAR delineation fused in Pinacle () to a CT then imported into PLATO (Nucletron, Netherlands) for applicator reconstruction and dosimetric determination based on GEC-ESTRO working group recommendations. In addition, a simultaneous plan was generated for each fraction optimized to point A. GTV and HRCTV D90 and V100 along with OAR D 0.1cc, 0.2cc, 0.5cc, 1cc, 2cc, and 5cc doses were calculated for each fraction. Data represents the mean difference SBP minus VGP. Positive numbers favor the ALATUS and negative numbers favor SBP. Results: When planned according to GEC-ESTRO recommendations mean intra-patient differences between Alatus VBP and SGP was HRCTV D90: -24.8 cGy and V100: -1.6 cc. Rectal D0.1cc :65.2 cGy, 0.2cc: 62.4 cGy, 0.5cc: 61.6 cGy, 1cc :58.8 cGy, 2cc: 58.4 cGy, 5cc :38.9 cGy. Bladder D0.1cc 93.2 cGy, 0.2cc 93.1 cGy, 0.5cc 56.7 cGy, 1cc 35.9 cGy, 2cc 32.9 cGy, 5cc 38.3 cGy. When planned with prescription dose to ICRU 38 defined point A mean intra-patient differences between Alatus VBP and SGP was HRCTV D90: 8.1 cGy and V100: 28.6 cc. Rectal D0.1cc :69.2 cGy, 0.2cc :65.7 cGy, 0.5cc: 57.9 cGy, 1cc 52.3 :cGy, 2cc:44.7 cGy, 5cc :26.8 cGy. Bladder D0.1cc :251.2 cGy, 0.2cc :224.6 cGy, 0.5cc :187.3 cGy, 1cc :148.8, 2cc 118.6, 5cc :93.1 cGy. Conclusions: Both rectal and vaginal dosimetry favored ALATUS balloon packing over Standard Gauze packing whether planned according to GEC-ESTRO or ICRU point A.HRCTV and D90 marginally favored SBP when planned to GEC-ESTRO guidelines but not when planned to Point A. This difference is likely due to the adaptive nature of treating a sequentially reduced volume rather than prescribing to a point. Author Disclosure: I.M. Ahmed, None; A.S. Saini, None; D. Hunt, None; W. Skinner, None; S.E. Finkelstein, None; M.C. Biagioli, None.
2461
Dosimetric Evaluation of Autosegmentation Software to Contour Normal Tissues in Multi-fractional HDR Brachytherapy for Cervical Cancer
A. M. Block, M. Quinn, N. D. Comsia, K. Albuquerque, J. C. Roeske Loyola University Medical Center, Maywood, IL Purpose/Objective(s): Previously, it was demonstrated that Atlas-Based Autosegmentation (ABAS, Elekta CMS, St. Louis, MO) could be used to contour normal organs in multi-fractional high dose rate (HDR) brachytherapy cases, despite difficulties that may arise from metal artifacts caused by the applicator. The goal of this study is to quantify the degree of autosegmented contour accuracy that is required to achieve a high level of dosimetric agreement with contours that are outlined by an expert user. Materials/Methods: The planning CT scans of 8 patients receiving multi-fractional HDR (5 fractions each) using tandem and ring or tandem and ovoids were considered in this study. Contours of the bladder and rectum were manually delineated on the first scan and using the ABAS software deformed to subsequent imaging sets. Independently, a physician contoured each of these structures on the same data sets. Using StructSure software (Standard Imaging Inc., Middleton, WI), the Dice Similarity Coefficient (DSC) was calculated for each organ using the ABAS and physician drawn contours. Values of the DSC close to 1 indicate good agreement while values closer to 0 indicate poor agreement. Dose volume histograms (DVHs) were also calculated using both sets of contours. DVH differences in mean dose and differences in dose to 2 cc (D2cc) were calculated for each fraction for each set of contours. The individual DSC values were then related to these differences, and the Mann-Whitney U test was used to assess significance.
S409
S408
Volume 78, Number 3, Supplement, 2010
Materials/Methods: Between 2000 and 2009, 39 patients with cervical cancer aged $ 75 years old received radiotherapy as definitive (34 patients) or postoperative adjuvant (5 patients) treatment at our institution. Median age was 78 years old (Range: 75 89). Thirty-seven patients had squamous cell carcinoma and 2 had adenocarcinoma. Twenty-four patients had FIGO I/II stage, 15 had III/IVA stage. Among 34 patients treated with definitive radiotherapy, 30 received external beam radiotherapy (EBRT) combined with intracavitary brachytherapy (ICBT), 3 received EBRT alone and 1 received ICBT alone. Among 5 patients treated with postoperative adjuvant radiotherapy, 3 received EBRT alone and 2 received EBRT combined with ICBT. Median total doses of EBRT and ICBT were 50.4 Gy (Range: 0 - 61.2) and 18.0 Gy (Range: 4.5 - 31.0), respectively. Three patients treated with definitive radiotherapy received concurrent chemotherapy using weekly cisplatin. Results: Median follow-up period was 18 months (Range: 1 - 85). Only 1 patient could not complete the treatment. Seven patients experienced recurrence (local: 4, para-aortic lymph node: 1, distant: 1, tumor marker elevation: 1). Nine patients died during the follow-up period. Five patients died due to the primary disease and 4 due to other causes. The 5-year overall and disease-specific survival (OS and DSS) rates of all patients were 55% and 78%, respectively. The 5-year OS rates in FIGOI/ II and III/IVA stage were 65% and 40%, respectively. The 5-year DSS rates in FIGO I/II and III/IVA stage were 88% and 66%, respectively. Grade 3 or greater late radiation toxicity occurred only in 2 patients (5%). One experienced hemorrhagic cystitis (Grade 3) after definitive radiotherapy, the other experienced adhesive intestinal obstruction (Grade 3) after postoperative adjuvant chemotherapy. Conclusions: Radiotherapy for elderly patients with cervical cancer was well tolerable and the survival outcomes were compatible with other previous reports. Our results indicate that radiotherapy is an useful modality for elderly patients with cervical cancer aged $ 75 years old and the importance of radiotherapy will be greater in the aging society. Author Disclosure: K. Yoshida, None; H. Nishimura, None; D. Miyawaki, None; T. Kawabe, None; Y. Okamoto, None; K. Nakabayashi, None; S. Yoshida, None; R. Sasaki, None; K. Sugimura, None.
2458
3D Image-based Customized Treatment Planning versus Standard Plans for Cervix Cancer HDR Brachytherapy
P. Mobit, M. C. Baird, M. R. Kanakamedala, W. F. Mourad, S. Vijayakumar, C. C. Yang University Of Mississippi Medical Center, Department of Radiation Oncology, Jackson, MS Purpose/Objective(s): To investigate the advantages of volumetric treatment planning in HDR brachytherapy for cervical carcinoma compared to standardized loading and 2D planning techniques. Materials/Methods: Our institution uses volume based 3D planning for each tandem and ovoid (T&O) insertion of HDR brachytherapy in the treatment of advanced cervical carcinoma. We attempt to define the benefits of this approach. We re-planned 70 CT based plans on 15 patients (treated in our facility between February, 2009-February, 2010) using a commonly used standard HDR loading of T&O. All patients received 4 fractions of 6.5 Gy or 5 fractions of 5.5 Gy to point H or A. The following organs at risk (OARs) were contoured: rectum, bladder, sigmoid and small bowel. Our customized planning requires adjustment of source dwell times and positions to keep doses to the OARs below 80% of prescription dose. The standardized HDR planning bases the loading on the length of the tandem. The dwell time for each tandem source position is the same. The dwell time multipliers for the ovoids were 0.33, 0.665 and 1.0 proportional to the 2 cm, 4 cm and 6 cm tandem length respectively. The dose to 2cc (D2cc) to OARs were analyzed, in addition to the volume covered by the prescription isodose and the maximum width and length of the pear shaped dose distribution for both the customized plan and the standardized plan. Results: In general, the dose to 2cc (D2cc) for the rectum and sigmoid was much lower with the customized planning technique. This dose was up to 60% lower for the customized plans for a 6.0 cm tandem. These differences in the D2cc for the rectum and sigmoid reduced when a 4 cm length tandem was used. In most cases, the D2cc of the bladder was lower for the standard plans compared to the customized ones. There was marked change in the D2cc for all OARs from one HDR session to the next with both the standard and customized plans. The pear shape dose distribution maximum width and length is smaller for the customized plans compared to the standard plan (was up to 1 cm) while the volume encompassed by the prescription isodose surface was up to 15% smaller than that obtained from the standard plan. Conclusions: Using customized plans for HDR T&O leads to reduced doses to the rectum, small bowels and sigmoid but the dose to the bladder was almost always higher. The dose to the small bowel could be up to 30% higher than the dose to point H or A in standard plans indicating that customized plans are superior to the standard ones for T&O for this group of patients. It is recommended to use CT/MRI images for any customized based HDR planning as the smaller treatment volume of the customized treatment plan makes geometric miss of the tumor volume more likely. Author Disclosure: P. Mobit, None; M.C. Baird, None; M.R. Kanakamedala, None; W.F. Mourad, None; S. Vijayakumar, None; C.C. Yang, None.
2459
Does Anesthesia during Cervical Cancer Brachytherapy Improve Implant Quality? 1
C. J. Anker , K. O’Donnell2, K. M. Boucher1, D. K. Gaffney1 1
University of Utah Huntsman Cancer Institute, Salt Lake City, UT, 2Oregon Health & Science University, Portland, OR
Purpose/Objective(s): To evaluate the relationship between anesthesia use and dose to objects-at-risk (OAR) in patients undergoing brachytherapy for cervix cancer. In addition, we sought to quantify the effects of high dose rate (HDR) brachytherapy technique and patient characteristics on dose distribution to OARs. Materials/Methods: From 1998 to 2008, 65 cervical cancer patients with FIGO stages IB1-IVA disease were identified receiving definitive external beam radiation and HDR brachytherapy with tandem and ovoid applicators. The 31 patients who had full dosimetric data were included in this analysis. Doses were recorded at point A, the ICRU-38 rectal point, ICRU-38 bladder point, and the vaginal surface. Generalized estimating equations were used to determine the significance of changes in OAR to point A dose ratios with differences in brachytherapy technique or patient characteristics.
Proceedings of the 52nd Annual ASTRO Meeting Results: Patients underwent a median of 5 brachytherapy procedures (range, 3-6), with a total of 179 procedures for 31 patients. For all brachytherapy treatments, the median ratios between the doses at the rectal, bladder, and vaginal surface reference points to those at point A were 0.48, 0.55, and 1.07, respectively. In general, decreased OAR dose was associated with increased ovoid size, increased tandem length, and earlier implant number. Anesthesia usage was not correlated with any of these favorable procedure characteristics, and its use was actually associated with increased bladder and vaginal surface dose. As expected, increased tandem curvature significantly increased the bladder dose and decreased rectal dose. As advanced age was associated with decreased ovoid size and increased tandem curvature, bladder dose increased as well. Higher FIGO stage was associated with decreased ovoid size and curvature, with resulting increased rectal dose. Conclusions: This study allowed identification of patient and procedure characteristics influencing OAR dosing. Of particular importance, the use of anesthesia did not correlate with decreased OAR dose in our series. Although the advent of 3D image-guided brachytherapy will bring new advances in treatment optimization, the actual technique involved at the time of the brachytherapy implant procedure will remain important. Author Disclosure: C.J. Anker, None; K. O’Donnell, None; K.M. Boucher, None; D.K. Gaffney, None.
2460
Initial Experience with Alatus Vaginal Balloon Packing (VBP) Compared to Standard Vaginal Gauze Packing (SGP) for Tandem and Ovoid Brachytherapy Treatment of Carcinoma of the Cervix
I. M. Ahmed, A. S. Saini, D. Hunt, W. Skinner, S. E. Finkelstein, M. C. Biagioli Moffitt Cancer Center, Tampa, FL Background: Brachytherapy in combination with external beam radiotherapy is standard treatment for locally advanced carcinoma of the cervix. Use of intracavitary implants requires appropriate vaginal packing to displace the rectum and bladder away from the radiation sources to minimize side-effects and complications. Typically, this is done via gauze packing, rectal retractor, and/or Foley balloon. Recently FDA approved Alatus VBP is an alternative form of vaginal packing for intracavitary brachytherapy. Purpose/Objective(s): We report initial experience with vaginal balloon packing (VBP) compared with standard gauze packing (SGP). Materials/Methods: Four patients undergoing fractionated HDR brachytherapy underwent alternating vaginal packing with either standard gauze packing (SGP) or with Alatus VBP. Brachytherapy was performed in 5 fractions, 600 cGy/ fraction, using a Royal Marsden applicator. Patients undergoing VBP, two balloons were used, one positioned anterior and second posterior to the ovoids and filled with normal saline. Brachytherapy planning was performed using an MRI for HRCTV and OAR delineation fused in Pinacle () to a CT then imported into PLATO (Nucletron, Netherlands) for applicator reconstruction and dosimetric determination based on GEC-ESTRO working group recommendations. In addition, a simultaneous plan was generated for each fraction optimized to point A. GTV and HRCTV D90 and V100 along with OAR D 0.1cc, 0.2cc, 0.5cc, 1cc, 2cc, and 5cc doses were calculated for each fraction. Data represents the mean difference SBP minus VGP. Positive numbers favor the ALATUS and negative numbers favor SBP. Results: When planned according to GEC-ESTRO recommendations mean intra-patient differences between Alatus VBP and SGP was HRCTV D90: -24.8 cGy and V100: -1.6 cc. Rectal D0.1cc :65.2 cGy, 0.2cc: 62.4 cGy, 0.5cc: 61.6 cGy, 1cc :58.8 cGy, 2cc: 58.4 cGy, 5cc :38.9 cGy. Bladder D0.1cc 93.2 cGy, 0.2cc 93.1 cGy, 0.5cc 56.7 cGy, 1cc 35.9 cGy, 2cc 32.9 cGy, 5cc 38.3 cGy. When planned with prescription dose to ICRU 38 defined point A mean intra-patient differences between Alatus VBP and SGP was HRCTV D90: 8.1 cGy and V100: 28.6 cc. Rectal D0.1cc :69.2 cGy, 0.2cc :65.7 cGy, 0.5cc: 57.9 cGy, 1cc 52.3 :cGy, 2cc:44.7 cGy, 5cc :26.8 cGy. Bladder D0.1cc :251.2 cGy, 0.2cc :224.6 cGy, 0.5cc :187.3 cGy, 1cc :148.8, 2cc 118.6, 5cc :93.1 cGy. Conclusions: Both rectal and vaginal dosimetry favored ALATUS balloon packing over Standard Gauze packing whether planned according to GEC-ESTRO or ICRU point A.HRCTV and D90 marginally favored SBP when planned to GEC-ESTRO guidelines but not when planned to Point A. This difference is likely due to the adaptive nature of treating a sequentially reduced volume rather than prescribing to a point. Author Disclosure: I.M. Ahmed, None; A.S. Saini, None; D. Hunt, None; W. Skinner, None; S.E. Finkelstein, None; M.C. Biagioli, None.
2461
Dosimetric Evaluation of Autosegmentation Software to Contour Normal Tissues in Multi-fractional HDR Brachytherapy for Cervical Cancer
A. M. Block, M. Quinn, N. D. Comsia, K. Albuquerque, J. C. Roeske Loyola University Medical Center, Maywood, IL Purpose/Objective(s): Previously, it was demonstrated that Atlas-Based Autosegmentation (ABAS, Elekta CMS, St. Louis, MO) could be used to contour normal organs in multi-fractional high dose rate (HDR) brachytherapy cases, despite difficulties that may arise from metal artifacts caused by the applicator. The goal of this study is to quantify the degree of autosegmented contour accuracy that is required to achieve a high level of dosimetric agreement with contours that are outlined by an expert user. Materials/Methods: The planning CT scans of 8 patients receiving multi-fractional HDR (5 fractions each) using tandem and ring or tandem and ovoids were considered in this study. Contours of the bladder and rectum were manually delineated on the first scan and using the ABAS software deformed to subsequent imaging sets. Independently, a physician contoured each of these structures on the same data sets. Using StructSure software (Standard Imaging Inc., Middleton, WI), the Dice Similarity Coefficient (DSC) was calculated for each organ using the ABAS and physician drawn contours. Values of the DSC close to 1 indicate good agreement while values closer to 0 indicate poor agreement. Dose volume histograms (DVHs) were also calculated using both sets of contours. DVH differences in mean dose and differences in dose to 2 cc (D2cc) were calculated for each fraction for each set of contours. The individual DSC values were then related to these differences, and the Mann-Whitney U test was used to assess significance.
S409