- Email: [email protected]
54 THE IMPACT OF CONTOURING SPECIALISTS ON THE PROCESS OF HEAD AND NECK IMRT TREATMENT PLANNING
CARO 2009 Conclusion: Both techniques have comparable dosimetric outcomes for target coverage and volumetric heart and lung doses. Photon boosts treat a significantly larger volume of normal breast, while electron deposit on average 50% more dose to the LAD for inner quadrant lesions. Thus, electrons should be avoided for targets within the inner quadrant; however, may be considered alternate to photons elsewhere to minimize irradiation of normal breast. 52 IMPLEMENTATION OF A SEMI-AUTOMATIC VERTEBRA DETECTION AND SEGMENTATION ALGORITHM FOR RADIOTHERAPY OF SPINOUS BONE METASTASES M. Martin, D. Letourneau, V. Pekar, R. Wong, M. Gospodarowicz, D. Jaffray University of Toronto, Princess Margaret Hospital, Toronto, ON Purpose: A one-step simulation and treatment process performed in a single 30-minute session on cone-beam CT (CBCT) enabled linac was implemented in our institution for radiotherapy of spinous bone metastases. To streamline the online planning process and eliminate manual segmentation a semi-automatic vertebra detection and segmentation algorithm referred to as the vertebra finder (VF) was developed. This study evaluates the performance and efficiency of the VF on CBCT data sets (DS) in terms of target identification and segmentation and the dosimetric coverage of the manually segmented targets. Materials and Methods: The detection and segmentation process of the VF was validated on the CBCT DS of 21 patients. The semi-automatic process involves manually placing a point on a known vertebral body, at which time the VF automatically segments and identifies by name all vertebrae stipulated to be contoured. Dose distributions were then generated using the auto-segmented targets from the VF. The VF success rate was defined as the ratio of correctly identified and segmented vertebrae to the total number of target vertebrae requested to be contoured for each patient DS. The time to complete the segmentation process was recorded and the dosimetric coverage of the manually segmented target was estimated using distributions generated from the VF targets. Results: The average success rate of the VF was 93.6% ±16.3 (21DS). The average time for automatic segmentation of target vertebrae was 0.80 minutes ±0.19, nearly five times less than the 3.86 minutes ±1.90 required for manual segmentation. The 95% isodose of the distributions produced with the VF volumes covers 99.42% ±0.75% of the manual PTV volumes. Conclusion: The semi-automatic vertebra detection and segmentation process was efficient and robust on CBCT DS. The dose distributions produced using the VF volumes provided adequate manual target coverage. Future work includes the clinical implementation of the VF in the one-step simulation and treatment process for the radiotherapy of spinous bone metastases. 53 CHANGING STRESS WHILE STRESSING CHANGE: THE ROLE OF INTERPROFESSIONAL EDUCATION (IPE) IN MEDIATING STRESS IN THE INTRODUCTION OF A TRANSFORMATIVE TECHNOLOGY SUCH AS IMAGE GUIDED RADIATION THERAPY (IGRT) C. Gillan1, K. Briggs2, N. Harnett2, D. Jaffray2, V. Leblanc2, S. Reeves2, D. Wiljer2, P. Catton2 1 Princess Margaret Hospital, Toronto, ON 2 University of Toronto, Princess Margaret Hospital, Toronto, ON Purpose: Changes in practice, as when introducing transformative technologies such as Image guided Radiation Therapy (IGRT), can place stress on interprofessional (IP) relationships and affect the success of the change initiative. This study was designed to assess if using an interprofessional education (IPE) approach when learning about IGRT can
September 30 – October 2009
S17
mediate this stress and facilitate development of a successful IP practice model. Materials and Methods: Oncologists, physicists and therapists who attended an IP IGRT Education Course were invited to participate in telephone interviews. Experiences introducing IGRT at participants’ home centres were sought, as were perceived benefits and stressors to IPE and to interprofessional practice (IPP) in the IGRT context. A modified grounded theory approach was used and data were analyzed using NVivo software. Results: Fourteen interviews were conducted and over 200min of interview time recorded. In introducing IGRT, participants noted stress relating to communication, compartmentalization of knowledge and allocation of professional responsibilities. IPE initiatives such as the IGRT Course offered common terminology, appreciation for others’ knowledge, and a holistic framework for practice. These outcomes were thought to foster increased collaboration and improved professional role definition regarding IGRT, with the perceived result of more efficient image approval processes and problem solving, and jointly written policies and protocols. Time constraints, power relations and acting as a change agent were noted to be residual stressors exacerbated by IPE, but were thought to be transient, likely overcome as a new practice framework was established. Conclusion: IPE can serve to facilitate implementation of a transformative technology such as IGRT through mediation of IP stress inherent in broadstroke change. Delivering IGRT education in an IPE format provides professionals a more holistic appreciation for the many aspects of the new technology. Transient stressors should be tolerated as a new model of IP IGRT practice is implemented. 54 THE IMPACT OF CONTOURING SPECIALISTS ON THE PROCESS OF HEAD AND NECK IMRT TREATMENT PLANNING H.B. Chan1, M. Vakilha1, J. Waldron1, N. Harnett1, S. Pearson1, M. Lau1, L. Zychla2 1 University of Toronto, Princess Margaret Hospital, Toronto, ON 2 McMaster University, Hamilton, ON Purpose: Head and neck intensity modulated radiation therapy (IMRT) treatment planning is one of the sites requiring time consuming delineation of a large number of targets and organ at risks. The present study was undertaken to determine the impact of having contour specialists (a Clinical Specialist Radiation Therapist and/or an internationally trained radiation oncologist) providing designated target and organ delineation on the contouring process of Head and Neck IMRT treatment planning. Materials and Methods: Contour specialists were integrated into the planning process by contouring organs at risk (OARs), enlarged neck nodes and nodal zones on head and neck patients (typically more than 20 region of interests [ROIs] for each patient). They also performed multimodality image fusion when required to assist target visualization. All contours were then reviewed and approved by the staff radiation oncologist who subsequently added the primary site GTV and all relevant CTVs for planning. Duration from CT simulation date to treatment start date for a three month period was compared before and after the introduction of contour specialists. Oncologists were asked to estimate the average time saving per patient. Results: One hundred and twenty-eight IMRT patients were treated in a three month period without contour specialists and 125 IMRT patients were treated in a three month period with contour specialists. Duration from CT simulation date to treatment start date improved from a mean of 17.2 days to 15.8 days while median improved from 17 days to 15 days. Oncologists estimated a mean contouring time saving of 51 minutes per patient and a mean image fusion time saving of 17 minutes per case.
S18 Conclusion: Having designated contour specialists has shortened the treatment planning time and reduced workload of radiation oncologists. These increased efficiencies should facilitate increased patient throughput. 55 CHANGES IN THE USE OF PALLIATIVE RADIOTHERAPY FOR BRAIN METASTASES IN ONTARIO D. Sutton1, K. Ding2, W. Mackillop2 1 Cancer Research Institute, Kingston, ON 2 Queen's University, Kingston, ON Purpose: Palliative Radiotherapy (PRT) plays an important role in the relief of neurologic symptoms in patients with brain metastases; however, little is known about the use of PRT on a population level. The purpose of this study was to describe temporal trends in the use of PRT for brain metastases in Ontario. Methods: The Ontario Cancer Registry was used to gather information on all cancer deaths in Ontario between the years 1984-2004. The proportion of these cases receiving at least one course of PRT for bone metastases within the last two years of life was described over time and by disease site. Results: There were 435,055 cancer deaths in Ontario during the study period. Of these cases, 4.0% received at least one course of PRT for brain mets within the last two years of life. The rate of PRT varied significantly by primary site (e.g. lung8.7%, breast-6.4%, kidney-5.0%, prostate-0.6%) (p<0.001). Over time, the proportion of cases receiving PRT for brain mets increased from 2.1% to 5.0% (p<0.001). This increasing trend remained significant after taking into account primary site, age, sex, and time from diagnosis till death (p<0.001). The rate over time also varied by primary site (e.g. lung- 5.3% to 11.2%, breast- 3.7% to 8.8%, kidney- 2.2% to 6.0%, prostate- 0 to 0.9%) (p<0.001). Conclusion: The rate of PRT for brain metastases in Ontario has significantly increased over time. Explanations for these trends will be discussed. 56 DOSIMETRIC TREATMENT EVALUATION AND OPTIMIZED REPLANNING FOR IMRT OF CERVIX CANCER J. Stewart1, K. Lim1, V. Kelly1, J. Xie1, K. Brock1, J. Moseley1, Y.-B. Cho1, A. Lundin2, H. Rehbinder2, A. Fyles1, D. Jaffray1, M. Milosevic1 1 Princess Margaret Hospital, Toronto, ON 2 RaySearch Laboratories AB, Stockholm, Sweden Purpose: The adoption of intensity modulated radiotherapy (IMRT) to treat cervix cancer has been limited by the risk of target underdosing caused by interfraction motion. This study evaluated the effectiveness of automated adaptive replanning during treatment, triggered by errors in target dose accumulation. Materials and Methods: Thirty-three patients with Stage IB-IVA cervix cancer underwent baseline CT/MRI and weekly MRI scans during standard radiotherapy treatment. Targets (GTV and CTV) and organs-at-risk (rectum, sigmoid, bladder, and bowel) were contoured on each image set. The CTV was the union of the GTV, cervix, parametria, upper vagina and lower uterus. A deformable registration algorithm (MORFEUS) was used to derive a mapping between patient anatomy at each fraction and the baseline anatomy. This model was used in research software (ORBIT Workstation, RaySearch Laboratories) to assess the dosimetric impact of interfraction motion. A plan was developed to deliver a dose to 98% volume (D98) of 50 Gy, 49 Gy, and 47.5 Gy to the GTV, CTV, and PTV (3mm isotropic margin), respectively. The accumulated dose (accounting for interfraction motion) was computed and compared to the planned dose after each weekly MRI scan. A replan without direct human intervention was triggered if the accumulated
CARO 2009 D98 to the GTV or CTV fell below 49 Gy or 47.5 Gy, respectively. Results: Of the 33 patients, 17 triggered at least one replan and the number of patients requiring one, two, and three replan(s) were 11, four, and two, respectively. Without dosimetric plan evaluation and replanning, eight patients failed the desired GTV D98 of 49 Gy and CTV D98 of 47.5 Gy at treatment completion, while all patients met both criteria using the replan strategy. Conclusion: Adaptive replanning is a feasible strategy to ensure target coverage for IMRT cervix treatments in the presence of anatomical motion. Automated replanning based on errors in target dose accumulation is a practical approach that minimizes both the number of interventions and the workload to implement a replan when necessary. 57 A POPULATION-BASED STUDY OF FACTORS AFFECTING ACCESS TO RADIOTHERAPY FOR ENDOMETRIAL CANCER IN ONTARIO T.P. Hanna, H. Richardson, P.Y. Peng, G. Li, W. Kong, J. Zhang-Salomons, W.J. Mackillop Queen's University, Kingston, ON Purpose: To describe use of post-operative radiation for endometrial cancer in Ontario. To identify system-related and patient-related factors affecting access to this treatment. Materials and Methods: We performed a retrospective cohort study of patients with surgically resected endometrial cancer in the Canadian province of Ontario between 1992-2003. Patients with evidence of incurable cancer at diagnosis or previous cancer diagnosis were excluded. We used multiple logistic regression to assess patient and system factors affecting radiation use. We controlled for disease-related factors: pelvic lymph node staging, histology, type of hysterectomy and peritoneal biopsy. We applied a mixed model to control for clustering of data by referring hospital. Results: 10,156 patients comprised the study cohort. The median age was 63 years. 27.5% received adjuvant radiation. The proportion of patients receiving radiation varied between cancer centre catchment areas from 19.7% to 35.9% (median 27.9%). In multivariate analysis, older patients were more likely to receive radiation up to the age of 80 (p<.0001). Patients who lived further from referral cancer centres were less likely to receive radiation (p<.01). Patients who had their surgery during high prevailing wait times at referral cancer centres were less likely to receive radiation (76-85 days OR 0.93 (0.79,1.09), 86-95 days OR 0.81 (0.67,0.98), 96-103 days OR 0.78 (0.62,0.98), >103 days OR 0.78 (0.59,1.02)). There was a 2.7-fold variation in the odds of radiation between cancer centre catchments (p<.0001). Management at a comprehensive gynecologic oncology centre, year of diagnosis and neighbourhood income quintile did not significantly affect the use of radiation. Conclusion: There is wide variation in use of radiation for endometrial cancer in Ontario. There is evidence that system factors unrelated to patient’s needs affect use of adjuvant radiation for endometrial cancer in Ontario. Age is a key patient-related factor affecting radiation use. 58 GENE EXPRESSION PROFILING IDENTIFIES BIOLOGIC PROCESSES PREDICTIVE OF RADIATION RESPONSE IN PATIENTS WITH ADVANCED CERVICAL CANCER C. Doll, P. Craighead, R. Diaz, M. Bieda, M. Eliasziw, P. Ghatage, S. Lees-Miller, A. Magliocco University of Calgary, Calgary, AB Objectives: To perform gene expression profiling in patients with cervical cancer treated with radiation therapy (RT), and to determine differences in gene expression between known non-responding and responding tumours in these patients.
September 30 – October 2009
S17
mediate this stress and facilitate development of a successful IP practice model. Materials and Methods: Oncologists, physicists and therapists who attended an IP IGRT Education Course were invited to participate in telephone interviews. Experiences introducing IGRT at participants’ home centres were sought, as were perceived benefits and stressors to IPE and to interprofessional practice (IPP) in the IGRT context. A modified grounded theory approach was used and data were analyzed using NVivo software. Results: Fourteen interviews were conducted and over 200min of interview time recorded. In introducing IGRT, participants noted stress relating to communication, compartmentalization of knowledge and allocation of professional responsibilities. IPE initiatives such as the IGRT Course offered common terminology, appreciation for others’ knowledge, and a holistic framework for practice. These outcomes were thought to foster increased collaboration and improved professional role definition regarding IGRT, with the perceived result of more efficient image approval processes and problem solving, and jointly written policies and protocols. Time constraints, power relations and acting as a change agent were noted to be residual stressors exacerbated by IPE, but were thought to be transient, likely overcome as a new practice framework was established. Conclusion: IPE can serve to facilitate implementation of a transformative technology such as IGRT through mediation of IP stress inherent in broadstroke change. Delivering IGRT education in an IPE format provides professionals a more holistic appreciation for the many aspects of the new technology. Transient stressors should be tolerated as a new model of IP IGRT practice is implemented. 54 THE IMPACT OF CONTOURING SPECIALISTS ON THE PROCESS OF HEAD AND NECK IMRT TREATMENT PLANNING H.B. Chan1, M. Vakilha1, J. Waldron1, N. Harnett1, S. Pearson1, M. Lau1, L. Zychla2 1 University of Toronto, Princess Margaret Hospital, Toronto, ON 2 McMaster University, Hamilton, ON Purpose: Head and neck intensity modulated radiation therapy (IMRT) treatment planning is one of the sites requiring time consuming delineation of a large number of targets and organ at risks. The present study was undertaken to determine the impact of having contour specialists (a Clinical Specialist Radiation Therapist and/or an internationally trained radiation oncologist) providing designated target and organ delineation on the contouring process of Head and Neck IMRT treatment planning. Materials and Methods: Contour specialists were integrated into the planning process by contouring organs at risk (OARs), enlarged neck nodes and nodal zones on head and neck patients (typically more than 20 region of interests [ROIs] for each patient). They also performed multimodality image fusion when required to assist target visualization. All contours were then reviewed and approved by the staff radiation oncologist who subsequently added the primary site GTV and all relevant CTVs for planning. Duration from CT simulation date to treatment start date for a three month period was compared before and after the introduction of contour specialists. Oncologists were asked to estimate the average time saving per patient. Results: One hundred and twenty-eight IMRT patients were treated in a three month period without contour specialists and 125 IMRT patients were treated in a three month period with contour specialists. Duration from CT simulation date to treatment start date improved from a mean of 17.2 days to 15.8 days while median improved from 17 days to 15 days. Oncologists estimated a mean contouring time saving of 51 minutes per patient and a mean image fusion time saving of 17 minutes per case.
S18 Conclusion: Having designated contour specialists has shortened the treatment planning time and reduced workload of radiation oncologists. These increased efficiencies should facilitate increased patient throughput. 55 CHANGES IN THE USE OF PALLIATIVE RADIOTHERAPY FOR BRAIN METASTASES IN ONTARIO D. Sutton1, K. Ding2, W. Mackillop2 1 Cancer Research Institute, Kingston, ON 2 Queen's University, Kingston, ON Purpose: Palliative Radiotherapy (PRT) plays an important role in the relief of neurologic symptoms in patients with brain metastases; however, little is known about the use of PRT on a population level. The purpose of this study was to describe temporal trends in the use of PRT for brain metastases in Ontario. Methods: The Ontario Cancer Registry was used to gather information on all cancer deaths in Ontario between the years 1984-2004. The proportion of these cases receiving at least one course of PRT for bone metastases within the last two years of life was described over time and by disease site. Results: There were 435,055 cancer deaths in Ontario during the study period. Of these cases, 4.0% received at least one course of PRT for brain mets within the last two years of life. The rate of PRT varied significantly by primary site (e.g. lung8.7%, breast-6.4%, kidney-5.0%, prostate-0.6%) (p<0.001). Over time, the proportion of cases receiving PRT for brain mets increased from 2.1% to 5.0% (p<0.001). This increasing trend remained significant after taking into account primary site, age, sex, and time from diagnosis till death (p<0.001). The rate over time also varied by primary site (e.g. lung- 5.3% to 11.2%, breast- 3.7% to 8.8%, kidney- 2.2% to 6.0%, prostate- 0 to 0.9%) (p<0.001). Conclusion: The rate of PRT for brain metastases in Ontario has significantly increased over time. Explanations for these trends will be discussed. 56 DOSIMETRIC TREATMENT EVALUATION AND OPTIMIZED REPLANNING FOR IMRT OF CERVIX CANCER J. Stewart1, K. Lim1, V. Kelly1, J. Xie1, K. Brock1, J. Moseley1, Y.-B. Cho1, A. Lundin2, H. Rehbinder2, A. Fyles1, D. Jaffray1, M. Milosevic1 1 Princess Margaret Hospital, Toronto, ON 2 RaySearch Laboratories AB, Stockholm, Sweden Purpose: The adoption of intensity modulated radiotherapy (IMRT) to treat cervix cancer has been limited by the risk of target underdosing caused by interfraction motion. This study evaluated the effectiveness of automated adaptive replanning during treatment, triggered by errors in target dose accumulation. Materials and Methods: Thirty-three patients with Stage IB-IVA cervix cancer underwent baseline CT/MRI and weekly MRI scans during standard radiotherapy treatment. Targets (GTV and CTV) and organs-at-risk (rectum, sigmoid, bladder, and bowel) were contoured on each image set. The CTV was the union of the GTV, cervix, parametria, upper vagina and lower uterus. A deformable registration algorithm (MORFEUS) was used to derive a mapping between patient anatomy at each fraction and the baseline anatomy. This model was used in research software (ORBIT Workstation, RaySearch Laboratories) to assess the dosimetric impact of interfraction motion. A plan was developed to deliver a dose to 98% volume (D98) of 50 Gy, 49 Gy, and 47.5 Gy to the GTV, CTV, and PTV (3mm isotropic margin), respectively. The accumulated dose (accounting for interfraction motion) was computed and compared to the planned dose after each weekly MRI scan. A replan without direct human intervention was triggered if the accumulated
CARO 2009 D98 to the GTV or CTV fell below 49 Gy or 47.5 Gy, respectively. Results: Of the 33 patients, 17 triggered at least one replan and the number of patients requiring one, two, and three replan(s) were 11, four, and two, respectively. Without dosimetric plan evaluation and replanning, eight patients failed the desired GTV D98 of 49 Gy and CTV D98 of 47.5 Gy at treatment completion, while all patients met both criteria using the replan strategy. Conclusion: Adaptive replanning is a feasible strategy to ensure target coverage for IMRT cervix treatments in the presence of anatomical motion. Automated replanning based on errors in target dose accumulation is a practical approach that minimizes both the number of interventions and the workload to implement a replan when necessary. 57 A POPULATION-BASED STUDY OF FACTORS AFFECTING ACCESS TO RADIOTHERAPY FOR ENDOMETRIAL CANCER IN ONTARIO T.P. Hanna, H. Richardson, P.Y. Peng, G. Li, W. Kong, J. Zhang-Salomons, W.J. Mackillop Queen's University, Kingston, ON Purpose: To describe use of post-operative radiation for endometrial cancer in Ontario. To identify system-related and patient-related factors affecting access to this treatment. Materials and Methods: We performed a retrospective cohort study of patients with surgically resected endometrial cancer in the Canadian province of Ontario between 1992-2003. Patients with evidence of incurable cancer at diagnosis or previous cancer diagnosis were excluded. We used multiple logistic regression to assess patient and system factors affecting radiation use. We controlled for disease-related factors: pelvic lymph node staging, histology, type of hysterectomy and peritoneal biopsy. We applied a mixed model to control for clustering of data by referring hospital. Results: 10,156 patients comprised the study cohort. The median age was 63 years. 27.5% received adjuvant radiation. The proportion of patients receiving radiation varied between cancer centre catchment areas from 19.7% to 35.9% (median 27.9%). In multivariate analysis, older patients were more likely to receive radiation up to the age of 80 (p<.0001). Patients who lived further from referral cancer centres were less likely to receive radiation (p<.01). Patients who had their surgery during high prevailing wait times at referral cancer centres were less likely to receive radiation (76-85 days OR 0.93 (0.79,1.09), 86-95 days OR 0.81 (0.67,0.98), 96-103 days OR 0.78 (0.62,0.98), >103 days OR 0.78 (0.59,1.02)). There was a 2.7-fold variation in the odds of radiation between cancer centre catchments (p<.0001). Management at a comprehensive gynecologic oncology centre, year of diagnosis and neighbourhood income quintile did not significantly affect the use of radiation. Conclusion: There is wide variation in use of radiation for endometrial cancer in Ontario. There is evidence that system factors unrelated to patient’s needs affect use of adjuvant radiation for endometrial cancer in Ontario. Age is a key patient-related factor affecting radiation use. 58 GENE EXPRESSION PROFILING IDENTIFIES BIOLOGIC PROCESSES PREDICTIVE OF RADIATION RESPONSE IN PATIENTS WITH ADVANCED CERVICAL CANCER C. Doll, P. Craighead, R. Diaz, M. Bieda, M. Eliasziw, P. Ghatage, S. Lees-Miller, A. Magliocco University of Calgary, Calgary, AB Objectives: To perform gene expression profiling in patients with cervical cancer treated with radiation therapy (RT), and to determine differences in gene expression between known non-responding and responding tumours in these patients.