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3D Dose Accumulation in Pseudo-Split-Field IMRT and BT for Locally Advanced Cervical Cancer
S490
International Journal of Radiation Oncology Biology Physics
fractionation schedules with respect to efficacy and toxicity of the treatment is currently being analyzed. Further directions include exploration of prognostic factors associated with inferior outcome. Author Disclosure: A. Lin: None. S. Voruganti: None. M. Patel: None. R. Hunter: None. J. An: None. G. Pond: None. I. Kong: None.
Author Disclosure: B. Sun: None. Y. Deshan: None. J. Esthappan: None. J. Garcia-Ramirez: None. S. Price: None. S. Mutic: None. J. Schwarz: None. P. Grigsby: None. K. Tanderup: None.
2704
Is Point A Still Relevant?: Does Prescribing to Tumor Volume Versus Point A Correspond to Equivalent Outcomes Among Cervical Cancer Patients Undergoing T&O Brachytherapy? R. Young, R. Yaparpalvi, H. Kuo, L. Hong, and K. Mehta; Albert Einstein College of Medicine/Montefiore, Bronx, NY
3D Dose Accumulation in Pseudo-Split-Field IMRT and BT for Locally Advanced Cervical Cancer B. Sun, Y. Deshan, J. Esthappan, J. Garcia-Ramirez, S. Price, S. Mutic, J. Schwarz, P. Grigsby, and K. Tanderup; Washington University in St. Louis, St. Louis, MO Purpose/Objective(s): Dose accumulation reporting of split field external beam radiotherapy (EBRT) and brachytherapy (BT) is challenging because of significant EBRT and BT dose gradients in the central pelvic region. The purpose of this study was to develop a method to determine biologically equivalent dose (BED) parameters for combined split-field IMRT and image guided BT in locally advanced cervical cancer. Materials/Methods: Patients were treated with pseudo-split-field IMRT with 50.4Gy in 28 fractions to the elective pelvic lymph node and the central pelvis region receiving 20 Gy. Patients received weekly image guided HDR with 6 fractions of 6.5 Gy. Each BT MR or CT dataset was registered with the IMRT planning CT dataset. A dose tracker program was developed to automate the equivalent dose computation in 2Gy fractions (EQD2) to GTV, rectum, bladder, sigmoid and point A. The dose, structures, and image registration exported from TPS in DICOM format were used for computation. For each voxel in the IMRT and BT image datasets, given the physical dose, fractionation and a/b ratio, EQD2 values were computed. Total DVH parameters for targets and OARs were computed on the 3D combined BED based on rigid image registration. Dose accumulation according to rigid alignment inherently assumes that the organ configuration during IMRT was identical to the BT anatomy. Therefore the uncertainty introduced by organ deformations between IMRT and BT was evaluated in 10 patients for OAR D2cc and GTV D90 by comparing dose to points in anterior rectum, posterior bladder, in the sigmoid loop closest to the applicator, and in the coldest region of the BT target. Results: According to ICRU and GEC ESTRO recommendations, D98, D90, D50 and D2cc EQD2 DVH parameters were computed for 20 patients (table 1). The uncertainties induced by organ deformation were -1 4Gy, -3 5Gy, 2 3Gy, and -3 5Gy for bladder, rectum, sigmoid and GTV, respectively. Therefore, this method was associated with a random uncertainty of 3-5Gy (SD) as well as systematic overestimation of bladder, rectum and GTV dose by 1-3Gy and underestimation of sigmoid dose by 2Gy. Conclusions: It is feasible to perform 3D EQD2 accumulation in order to assess high and intermediate dose regions for combined split field IMRT and BT. The assessment of accumulated dose was associated with uncertainties of 3-5Gy (SD). Further improvement of accuracy of dose assessment for split-field IMRT combined with BT, would require accurate deformable registration in the pelvis which is limited by anatomical variations induced by the insertion of applicator.
2705
Purpose/Objective(s): Brachytherapy is an essential component of curative treatment in cervical cancer. Although techniques have improved with more conformal treatment planning, the prescription system is still largely based on dated methods with doses assigned to fixed points irrespective of tumor topography or organs at risk (OAR). Dosimetric studies have shown that prescribing to or modifying 3D treatment plans based on Point A calculations is not necessary for tumor coverage, but clinical outcomes have not been extensively reviewed, although we believe they will be equivalent. This analysis reviews outcomes in women treated with tandem and ovoid (T&O) brachytherapy at our institution. Materials/Methods: Twenty women with FIGO Stage IB1-IIB cervical carcinoma, treated with concurrent cisplatin and EBRT followed by HDR T&O brachytherapy treatments between 6/2006 and 6/2012 at the Montefiore Einstein Center for Cancer Care, were identified. Charts and patient data were reviewed retrospectively to assess for toxicity and disease status. A total of 84 brachytherapy plans were reviewed, and all point A doses were recorded. These values were averaged and compared to the volumetrically-based prescription dose of 6 Gy for each of the 5 fractions. The median follow-up was 24 months. One patient was FIGO Stage IB1, 8 were Stage IB2, 3 were Stage IIA, and 8 were Stage IIB. All patients underwent external beam to the pelvis to 45 Gy in 25 fractions. T&O insertions and HDR brachytherapy treatments were administered 1-2 times per week. An optimal treatment plan was created for each insertion for the best dosimetric fit to the 3D target, as delineated by physician contouring. Point A doses were recorded, but no attempts were made to equate Point A and prescription doses. Results: Median cumulative Point A dose was 26.85 Gy (19.30-29.20), corresponding to 90% of the volumetrically-prescribed dose of 30 Gy pertreatment. With a median follow-up of 24 months, 15 of the 20 patients (75%) are alive with NED. 4 of the 20 patients (20%) progressed, oneof whom is deceased. 3 patients failed first locally and then distantly, with local failure at 1 month, 12.9 months, and 16 months. There were no acute toxicities above RTOG Grade 2. There was one late RTOG Grade 3 toxicity of vaginal canal stenosis. Conclusions: Our clinical outcomes are equivalent to published rates for similarly-staged cervical cancer patients. These results suggest that brachytherapy planning and treatment based solely on 3D image-based systems, in which plans are not modified for Point A doses, are at least comparable to traditional prescription and planning systems. We look forward to expanding our database and continuing to evaluate outcomes. Author Disclosure: R. Young: None. R. Yaparpalvi: None. H. Kuo: None. L. Hong: None. K. Mehta: None.
Scientific Abstract 2704; Table Parameters Point A GTV D98 D90 D50 Bladder D50 D2cc Rectum D50 D2cc Sigmoid D50 D2cc
Mean value 1 standard deviation (Gy) 91.4 7.9 86.7 29.8 101.3 36.2 166.6 91.1 59.7 7.8 101.1 11.7 35.4 7.4 68.1 13 48.9 7.5 72.3 11.1
2706 Is There a Difference in Cause-Specific Survival and Overall Survival in 1B1 Squamous Cell Carcinoma and Adenocarcinoma of the Uterine Cervix?: SEER Database 2004-2008 A. Herskovic, W. Yan, P. Christos, D. Nori, C. Chao, and A. Ravi; Weill Cornell Medical College, New York, NY Purpose/Objective(s): To determine the significance of histology and treatment modality on overall survival (OS) and cause-specific survival (CSS) in stage IB1 cervical carcinoma. Materials/Methods: Cases of stage IB1 squamous cell carcinoma (SCC) and adenocarcinoma (AC) of the uterine cervix managed with either radical hysterectomy (RAH), local tumor destruction (including methods
International Journal of Radiation Oncology Biology Physics
fractionation schedules with respect to efficacy and toxicity of the treatment is currently being analyzed. Further directions include exploration of prognostic factors associated with inferior outcome. Author Disclosure: A. Lin: None. S. Voruganti: None. M. Patel: None. R. Hunter: None. J. An: None. G. Pond: None. I. Kong: None.
Author Disclosure: B. Sun: None. Y. Deshan: None. J. Esthappan: None. J. Garcia-Ramirez: None. S. Price: None. S. Mutic: None. J. Schwarz: None. P. Grigsby: None. K. Tanderup: None.
2704
Is Point A Still Relevant?: Does Prescribing to Tumor Volume Versus Point A Correspond to Equivalent Outcomes Among Cervical Cancer Patients Undergoing T&O Brachytherapy? R. Young, R. Yaparpalvi, H. Kuo, L. Hong, and K. Mehta; Albert Einstein College of Medicine/Montefiore, Bronx, NY
3D Dose Accumulation in Pseudo-Split-Field IMRT and BT for Locally Advanced Cervical Cancer B. Sun, Y. Deshan, J. Esthappan, J. Garcia-Ramirez, S. Price, S. Mutic, J. Schwarz, P. Grigsby, and K. Tanderup; Washington University in St. Louis, St. Louis, MO Purpose/Objective(s): Dose accumulation reporting of split field external beam radiotherapy (EBRT) and brachytherapy (BT) is challenging because of significant EBRT and BT dose gradients in the central pelvic region. The purpose of this study was to develop a method to determine biologically equivalent dose (BED) parameters for combined split-field IMRT and image guided BT in locally advanced cervical cancer. Materials/Methods: Patients were treated with pseudo-split-field IMRT with 50.4Gy in 28 fractions to the elective pelvic lymph node and the central pelvis region receiving 20 Gy. Patients received weekly image guided HDR with 6 fractions of 6.5 Gy. Each BT MR or CT dataset was registered with the IMRT planning CT dataset. A dose tracker program was developed to automate the equivalent dose computation in 2Gy fractions (EQD2) to GTV, rectum, bladder, sigmoid and point A. The dose, structures, and image registration exported from TPS in DICOM format were used for computation. For each voxel in the IMRT and BT image datasets, given the physical dose, fractionation and a/b ratio, EQD2 values were computed. Total DVH parameters for targets and OARs were computed on the 3D combined BED based on rigid image registration. Dose accumulation according to rigid alignment inherently assumes that the organ configuration during IMRT was identical to the BT anatomy. Therefore the uncertainty introduced by organ deformations between IMRT and BT was evaluated in 10 patients for OAR D2cc and GTV D90 by comparing dose to points in anterior rectum, posterior bladder, in the sigmoid loop closest to the applicator, and in the coldest region of the BT target. Results: According to ICRU and GEC ESTRO recommendations, D98, D90, D50 and D2cc EQD2 DVH parameters were computed for 20 patients (table 1). The uncertainties induced by organ deformation were -1 4Gy, -3 5Gy, 2 3Gy, and -3 5Gy for bladder, rectum, sigmoid and GTV, respectively. Therefore, this method was associated with a random uncertainty of 3-5Gy (SD) as well as systematic overestimation of bladder, rectum and GTV dose by 1-3Gy and underestimation of sigmoid dose by 2Gy. Conclusions: It is feasible to perform 3D EQD2 accumulation in order to assess high and intermediate dose regions for combined split field IMRT and BT. The assessment of accumulated dose was associated with uncertainties of 3-5Gy (SD). Further improvement of accuracy of dose assessment for split-field IMRT combined with BT, would require accurate deformable registration in the pelvis which is limited by anatomical variations induced by the insertion of applicator.
2705
Purpose/Objective(s): Brachytherapy is an essential component of curative treatment in cervical cancer. Although techniques have improved with more conformal treatment planning, the prescription system is still largely based on dated methods with doses assigned to fixed points irrespective of tumor topography or organs at risk (OAR). Dosimetric studies have shown that prescribing to or modifying 3D treatment plans based on Point A calculations is not necessary for tumor coverage, but clinical outcomes have not been extensively reviewed, although we believe they will be equivalent. This analysis reviews outcomes in women treated with tandem and ovoid (T&O) brachytherapy at our institution. Materials/Methods: Twenty women with FIGO Stage IB1-IIB cervical carcinoma, treated with concurrent cisplatin and EBRT followed by HDR T&O brachytherapy treatments between 6/2006 and 6/2012 at the Montefiore Einstein Center for Cancer Care, were identified. Charts and patient data were reviewed retrospectively to assess for toxicity and disease status. A total of 84 brachytherapy plans were reviewed, and all point A doses were recorded. These values were averaged and compared to the volumetrically-based prescription dose of 6 Gy for each of the 5 fractions. The median follow-up was 24 months. One patient was FIGO Stage IB1, 8 were Stage IB2, 3 were Stage IIA, and 8 were Stage IIB. All patients underwent external beam to the pelvis to 45 Gy in 25 fractions. T&O insertions and HDR brachytherapy treatments were administered 1-2 times per week. An optimal treatment plan was created for each insertion for the best dosimetric fit to the 3D target, as delineated by physician contouring. Point A doses were recorded, but no attempts were made to equate Point A and prescription doses. Results: Median cumulative Point A dose was 26.85 Gy (19.30-29.20), corresponding to 90% of the volumetrically-prescribed dose of 30 Gy pertreatment. With a median follow-up of 24 months, 15 of the 20 patients (75%) are alive with NED. 4 of the 20 patients (20%) progressed, oneof whom is deceased. 3 patients failed first locally and then distantly, with local failure at 1 month, 12.9 months, and 16 months. There were no acute toxicities above RTOG Grade 2. There was one late RTOG Grade 3 toxicity of vaginal canal stenosis. Conclusions: Our clinical outcomes are equivalent to published rates for similarly-staged cervical cancer patients. These results suggest that brachytherapy planning and treatment based solely on 3D image-based systems, in which plans are not modified for Point A doses, are at least comparable to traditional prescription and planning systems. We look forward to expanding our database and continuing to evaluate outcomes. Author Disclosure: R. Young: None. R. Yaparpalvi: None. H. Kuo: None. L. Hong: None. K. Mehta: None.
Scientific Abstract 2704; Table Parameters Point A GTV D98 D90 D50 Bladder D50 D2cc Rectum D50 D2cc Sigmoid D50 D2cc
Mean value 1 standard deviation (Gy) 91.4 7.9 86.7 29.8 101.3 36.2 166.6 91.1 59.7 7.8 101.1 11.7 35.4 7.4 68.1 13 48.9 7.5 72.3 11.1
2706 Is There a Difference in Cause-Specific Survival and Overall Survival in 1B1 Squamous Cell Carcinoma and Adenocarcinoma of the Uterine Cervix?: SEER Database 2004-2008 A. Herskovic, W. Yan, P. Christos, D. Nori, C. Chao, and A. Ravi; Weill Cornell Medical College, New York, NY Purpose/Objective(s): To determine the significance of histology and treatment modality on overall survival (OS) and cause-specific survival (CSS) in stage IB1 cervical carcinoma. Materials/Methods: Cases of stage IB1 squamous cell carcinoma (SCC) and adenocarcinoma (AC) of the uterine cervix managed with either radical hysterectomy (RAH), local tumor destruction (including methods