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Radium-223 in Metastatic Castration–Resistant Prostate Cancer: Single-Institution Analysis of Factors Associated With Treatment Completion and Survival
E260
International Journal of Radiation Oncology Biology Physics
Conclusion: Remarkably, employing AuNP agent in prostate not only significantly increases dose to the target but also decreases dose to the neighboring rectum and even urethra, which is embedded within the prostate. These are mutually interdependent effects as more enhancement leads to more shielding and vice-versa. This technique has the potential to benefit HR prostate patients with bulky tumors, as well as other prostate cancer patient categories through dose de-escalation: patients requiring salvage re-irradiation for local recurrence, patients with large prostate/ rectum contact or patients under anticoagulant therapy. Furthermore the technique can be extended to HDR brachytherapy with 192-Ir and be applied to other tumor types such as gynecologic cancer. However, the higher energy and larger penetration depth of 192-Ir makes it less favorable than 125-I. Author Disclosure: D. Brivio: None. P.L. Nguyen: Consulting; Ferring. E. Sajo: None. W. Ngwa: None. P. Zygmanski: None.
2632
2631 Correlation Between V150 of Prostate and D30, D5 of Urethra in Postimplant Analysis C. Yan; UPMC, Pittsburgh, PA Purpose/Objective(s): Several studies have shown an improved outcome and a survival benefit from triple modality therapy that included the low dose brachytherapy (LDR) to prostate cancer. This has led to the increased inclusion of the LDR in treating prostate cancer. An important goal of LDR is to maximize target coverage while control dose to critical structures such as urethra and rectum. Among the widespread metrics used in post-implant report are D90, V150 for prostate, D30, and D5 for urethra and V100 for rectum. However, there is very little consensus with regard to what metrics should be used for an indicator to further minimize treatmentrelated morbidity during post-implant report. There is also evidence that high-dose regions within the gland which D90, V150 convey, do not portend complications. The aim of this study was to evaluate the correlation between V150 and the more representative dose D30, D5 to the urethra as well as the prostate coverage D90. Materials/Methods: Fifty patients that received real-time dosimetric, intraoperative LDR prostate brachytherapy from January 2014-2016 were analyzed. The implants included both I-125 and Pd-103. Prescriptions followed the guidelines of AAPM TG-137. During postimplant analysis, a Coude-tip Foley catheter was used during imaging for each case to facilitate the delineation of urethra. T2-cubed MRI was acquired and fused with the CT scan for accurate delineation of the prostate. MRI and CT were acquired on the same day about 30 days after the LDR procedure. An institutionally-based peer-reviewed process and document was established based on national recommendations. Target dose for V150 is 50%, and D30 and D5 are <125% and <150% of prescribed dose. The numbers of implants that failed to meet the V150 but met the D30 or D5 were analyzed. Results: Out of the 50 implants, only 17 of them did not exceed the postimplant dosimetry target for V150 50%. Twenty-two of the 33 implants met the optimal dosimetry targets for both D30 and D5, and the other 11 of the 33 implants failed to meet either the D30 or the D5. For all 50 implants, the D90 was achieved, falling between 80% and 120% of prescribed dose. For 5 of the implants, D90 is less than 90%, but only 2 out of the 5 achieved the V150 target. All the implants met the target dose for rectum: V1001.3cc. Conclusion: The fact that majority of the implants failed to meet V150 target, but met both the D30 and D5 for urethra implies that V150 is not an accurate surrogate of urethra dose or acute morbidity. This study shows that in an effort to improve quality of life while achieving a survival benefit, it may be more important to accurately delineate the urethra, and report D30, D5 in post-implant analysis. Continued clinical study is needed to evaluate whether D30 and D5 can better predict urinary complications. Author Disclosure: C. Yan: None.
Management of Prostate Cancer Using Magnetic Resonance Guided Pulsed Focused Ultrasound-Mediated Targeted Chemotherapeutic Agent Delivery L. Chen, D. Cvetkovic, B. Wang, R. Gupta, and C.M.C. Ma; Fox Chase Cancer Center, Philadelphia, PA Purpose/Objective(s): The purpose of this study is to investigate an approach to prostate cancer therapy using nanodroplet-encapsulated drugs combined with pulsed high intensity focused ultrasound (pFUS) treatment. Materials/Methods: Human prostate tumor (LNCaP) cells were implanted into the prostates of nude mice. Tumor growth was monitored using MRI. When tumor volumes reached 140 10 mm3 on MRI, the tumorebearing mice were randomly divided into 5 groups (n Z 5 for each group). Group 1, animals were treated with an IV injection of docetaxel-encapsulated nanodroplets (ND-DTX) + pFUS. Animals in Group 2 were treated with pFUS alone. Animals in Group 3 were injected (IV) with DTX-encapsulated nanodroplets alone, Group 4 received free DTX alone and Group 5 was used as a control group. The formulation of the DTX-encapsulated nanodroplets was: DTX dose 20 mg/kg, Nanoemulsion composition 0.5% PTX, 1% perfluorocarbon and 2% stabilizing block copolymer. The MRgFUS treatment was performed on a clinical HIFU (high intensity focused ultrasound) device (ExAblate 2000, InSightec-Tx-Sonics, Haifa, Israel, and Dallas, TX) together with a 1.5 T GE MR scanner. During the animal treatment, phase MR images were used for the temperature measurement in the treatment target. The MRgFUS system was capable of both treatment planning and treatment monitoring in near real-time (with a 3 second delay). After treatment, animals were allowed to survive for 3 weeks. Tumor growth delay was monitored by MRI (resolution: <0.2mm). Ultrasound treatment parameters were 1MHz, 25W acoustic power, 10% duty cycle and 60 sec for each sonication. Multiple treatment spots (8-12) were used to cover the whole tumor depending on the individual tumor sizes. Results: Using our focused ultrasound treatment protocol described above the temperature elevation was less than 5 C in the treatment volume for all animals treated resulting in absolute temperature of less than 42 C after general anesthesia. The time for the entire MRgFUS treatment procedure was approximately 1 hour including animal anesthesia and treatment setup. All animals tolerated the ultrasound treatment well. Our study results showed that group 1, in which animals were treated with an IV injection of docetaxel-encapsulated nanodroplets (ND-DTX) + pFUS, exhibited the most tumor growth delay (50% - 30%) among all groups. All other groups showed similar tumor growth to that of the control group after the treatment (within statistical uncertainties). Conclusion: Our preliminary results showed a great potential for prostate cancer therapy using targeted DTX+ nanodroplets, which could be activated by pFUS. Further animal studies are warranted to confirm the results quantitatively. The mechanisms of the treatment effect are being studied histologically. Author Disclosure: L. Chen: None. D. Cvetkovic: None. B. Wang: None. R. Gupta: None. C. Ma: None.
2633 Radium-223 in Metastatic CastrationeResistant Prostate Cancer: Single-Institution Analysis of Factors Associated With Treatment Completion and Survival A. Bang,1 S. Malone,1 E.Y.C. Leung,2 C. Canil,1 L. Eapen,1 and S.C. Morgan1; 1The Ottawa Hospital Cancer Centre, Ottawa, ON, Canada, 2The Ottawa Hospital, Ottawa, ON, Canada Purpose/Objective(s): Radium-223 (Ra-223), an alpha particle-emitting radionuclide, is the first bone-targeted therapy demonstrated to improve survival in metastatic castration-resistant prostate cancer (mCRPC). We report our institution’s experience, exploring the association between mCRPC therapies received prior to Ra-223 and treatment outcomes.
Volume 96 Number 2S Supplement 2016 Materials/Methods: The outcomes of patients with progressive, symptomatic mCRPC with bone metastases treated with Ra-223 between Oct. 2009 and Dec. 2015 were analyzed. The association between baseline characteristics and outcomes were analyzed using descriptive statistics while overall survival (OS) was estimated using the Kaplan-Meier method. Toxicities were assessed using NCI CTCAE v4.0. Results: A total of 36 patients were analyzed. Median follow-up was 6.8 months (range, 1.5-34.7). Median age was 75 years (range, 49-88). Prior to commencing Ra-223, 14 patients (39%) were treated with abiraterone acetate (abi), 17 patients (47%) with enzalutamide (enza), and 14 patients (39%) with docetaxel; 16 patients (44%) received more than one agent and 7 (19%) received none. The median number of Ra-223 injections received was 5 (range, 1-6). Nineteen patients (53%) discontinued therapy prematurely. Median OS for the total cohort was 10.0 months (95% CI, 4.5-15.0). There was a non-significant trend towards shorter OS in those patients that had received prior abi or enza vs. those that had received neither of these agents (median 6.8 vs. 14.0 months; HR 2.67; 95% CI, 0.87-8.20; log-rank P Z 0.087). Forty-four percent of patients who received prior abi/enza completed all 6 planned injections vs. 55% of those that did not. There were differences seen in the baseline characteristics of these two groups: mean PSA 272 vs. 114 mcg/L, and proportion with 20 metastases 64% vs. 44%, respectively. Cumulative incidence of grade 3 hematologic toxicity during or after treatment was as follows: anemia 19%, neutropenia 0%, and thrombocytopenia 11%. Conclusion: This cohort of patients receiving Ra-223 spans the era prior to the advent of abi and enza and thus included patients with and without prior exposure to these agents. Patients receiving these agents prior to commencing Ra-223 were less likely to complete the 6 planned injections, and had a non-significant trend toward shorter survival, raising the hypothesis that earlier integration of Ra-223 in the mCRPC disease course may be preferred. This apparent association may reflect greater disease burden in more heavily pre-treated patients, rather than diminished efficacy of Ra-223. Finally, the toxicity profile of Ra-223 observed in this realworld setting was relatively favorable and comparable to that seen in the phase III trial that led to regulatory approval. Author Disclosure: A. Bang: None. S. Malone: Independent Contractor; The Ottawa Hospital. E.Y. Leung: Independent Contractor; The Ottawa Hospital. C. Canil: Independent Contractor; The Ottawa Hospital. L. Eapen: Independent Contractor; The Ottawa Hospital. S.C. Morgan: Independent Contractor; The Ottawa Hospital.
2634 Stereotactic Body Radiation Therapy to the Prostate: Patterns of Care in the National Cancer Data Base J.P. Weiner,1,2 D. Schwartz,1,2 M. Shao,1,2 V. Osborn,1,2 and D. Schreiber1,2; 1SUNY Downstate Medical Center, Brooklyn, NY, 2 Veterans Affairs NY Harbor Healthcare System, Brooklyn, NY Purpose/Objective(s): To analyze the utilization and patterns of care of stereotactic body radiation therapy (SBRT) in the treatment of prostate cancer. Materials/Methods: Men who were diagnosed with localized prostate cancer between 2004 and 2012 and treated with radiation therapy were included. Men were categorized as receiving external beam radiation, prostate brachytherapy, or SBRT to the prostate or pelvis. Descriptive statistics were used to analyze stereotactic radiation therapy usage and compared via Chi Square or Fisher’s Exact Test. Results: There were 299,186 patients identified, of which 5,078 (1.7%) were identified as receiving SBRT. Of those, 2,108 had low risk disease (41.5%), 2,251 had intermediate risk disease (44.3%) and 719 had high risk disease (14.2%). The relative utilization of SBRT increased from 0.1% in 2004 to 4.0% in 2012 (P<0.001). The relative utilization over time increased more rapidly in academic programs from 0.1% in 2004 to 7.1% of all patients receiving radiation in 2012 (P<0.001). In non-academic programs, there was a slower increase in utilization from 0.1% in 2004 to 2.6% in 2012. The most commonly utilized fractionation scheme included
Poster Viewing E261 5 fractions in 4,635 patients (91.3%), with 725 cGy x 5 the most common fractionation scheme (49.6%) followed by 700 cGy x 5 (21.3%). Doses of 750 cGy per day were more commonly utilized in non-academic centers (32.3%) compared to academic centers (26.1%). Conclusion: SBRT is slowly increasing acceptance, but more so in academic facilities. 700-725 cGy x 5 fractions appears to be the most commonly utilized fractionation scheme. As further long-term data regarding the safety and efficacy emerges, the relative utilization of SBRT is expected to continue to increase. Author Disclosure: J.P. Weiner: None. D. Schwartz: None. M. Shao: None. V. Osborn: None. D. Schreiber: None.
2635 Vector Analysis of Bladder Cancer Patient Setup Utilizing a Magnetic Resonance Image Guided Radiation Therapy (MR-IGRT) System B.W. Fischer-Valuck, O.L. Green, S. Mutic, H.A. Gay, and J.M. Michalski; Washington University School of Medicine, St. Louis, MO Purpose/Objective(s): Inter and intra-fraction anatomy changes in patients undergoing radiation therapy (RT) for bladder cancer (BC) are common but have thus far been studied with implanted fiducial markers, limited quality 2-D orthogonal films and computed tomography (CT). The adverse impact of daily set-up variation could be more significant than appreciated. Our goal was to employ the soft tissue imaging capabilities of an integrated magnetic resonance image-guided RT (MR-IGRT) system to analyze daily positioning. Materials/Methods: Fourteen patients with BC were treated on a MRIGRT system. Patient setup was performed via volumetric MR imaging with a resolution of 0.15 x 0.15 cm. Alignment was performed according to skin marks then shifts assessed by comparing the treatment volume from the planning CT to the daily MR image. Two hundred forty pretreatment MR images were analyzed and 3 shifts were recorded for each image. A vector shift was calculated by combining the square root of the combined sum of the shifts squared. Number of times that the vector of combined shifts would have exceeded the planning tumor volume (PTV) was recorded. Results: The daily volumetric MR imaging allowed for accurate alignment and daily monitoring of bladder volume and normal tissue anatomy. Recorded shifts of the treated volume were 0.90.5 cm in the right/left direction, 0.70.3 cm in the anterior/posterior direction, and 0.70.4 cm in the cranio-caudal direction. In 66 (28%) of cases the vector shift was initially greater than the PTV margin. For 2 patients, pre-treatment MR imaging revealed the tumor reduced in size and dose to the bowel would have exceeded constraints, and treatment adaptation was performed to reduce normal tissue toxicity. Using CTCAE criteria, no grade 3 or higher toxicities have been reported. Conclusion: Accurate and reproducible treatment delivery is required to avoid marginal misses to the target volume as well as excess dose to normal tissue. MR-IGRT allows for excellent soft tissue visualization which enables for the avoidance of potential setups errors by allowing daily alignment changes to ensure the target is included in the PTV. It also allows the ability to make treatment changes based on anatomy variations. Author Disclosure: B.W. Fischer-Valuck: None. O.L. Green: Honoraria; ViewRay. S. Mutic: Research Grant; ViewRay. Honoraria; ViewRay. Consultant; ViewRay. Advisory Board; ViewRay. Travel Expenses; ViewRay. Stock; ViewRay. Royalty; ViewRay. H.A. Gay: None. J.M. Michalski: None.
2636 The Effect of Lovastatin on Preservation of Erectile Function After Radiation Therapy (RT) for Prostate Cancer: Secondary Analysis of a Prospective Study M.S. Anscher,1 M.G. Chang,2 D. Moghanaki,3 M. Rosu,4 R.B. Mikkelsen,4 D. Holdford,5 V. Skinner,6 B.M. Grob,1 A. Sanyal,1
International Journal of Radiation Oncology Biology Physics
Conclusion: Remarkably, employing AuNP agent in prostate not only significantly increases dose to the target but also decreases dose to the neighboring rectum and even urethra, which is embedded within the prostate. These are mutually interdependent effects as more enhancement leads to more shielding and vice-versa. This technique has the potential to benefit HR prostate patients with bulky tumors, as well as other prostate cancer patient categories through dose de-escalation: patients requiring salvage re-irradiation for local recurrence, patients with large prostate/ rectum contact or patients under anticoagulant therapy. Furthermore the technique can be extended to HDR brachytherapy with 192-Ir and be applied to other tumor types such as gynecologic cancer. However, the higher energy and larger penetration depth of 192-Ir makes it less favorable than 125-I. Author Disclosure: D. Brivio: None. P.L. Nguyen: Consulting; Ferring. E. Sajo: None. W. Ngwa: None. P. Zygmanski: None.
2632
2631 Correlation Between V150 of Prostate and D30, D5 of Urethra in Postimplant Analysis C. Yan; UPMC, Pittsburgh, PA Purpose/Objective(s): Several studies have shown an improved outcome and a survival benefit from triple modality therapy that included the low dose brachytherapy (LDR) to prostate cancer. This has led to the increased inclusion of the LDR in treating prostate cancer. An important goal of LDR is to maximize target coverage while control dose to critical structures such as urethra and rectum. Among the widespread metrics used in post-implant report are D90, V150 for prostate, D30, and D5 for urethra and V100 for rectum. However, there is very little consensus with regard to what metrics should be used for an indicator to further minimize treatmentrelated morbidity during post-implant report. There is also evidence that high-dose regions within the gland which D90, V150 convey, do not portend complications. The aim of this study was to evaluate the correlation between V150 and the more representative dose D30, D5 to the urethra as well as the prostate coverage D90. Materials/Methods: Fifty patients that received real-time dosimetric, intraoperative LDR prostate brachytherapy from January 2014-2016 were analyzed. The implants included both I-125 and Pd-103. Prescriptions followed the guidelines of AAPM TG-137. During postimplant analysis, a Coude-tip Foley catheter was used during imaging for each case to facilitate the delineation of urethra. T2-cubed MRI was acquired and fused with the CT scan for accurate delineation of the prostate. MRI and CT were acquired on the same day about 30 days after the LDR procedure. An institutionally-based peer-reviewed process and document was established based on national recommendations. Target dose for V150 is 50%, and D30 and D5 are <125% and <150% of prescribed dose. The numbers of implants that failed to meet the V150 but met the D30 or D5 were analyzed. Results: Out of the 50 implants, only 17 of them did not exceed the postimplant dosimetry target for V150 50%. Twenty-two of the 33 implants met the optimal dosimetry targets for both D30 and D5, and the other 11 of the 33 implants failed to meet either the D30 or the D5. For all 50 implants, the D90 was achieved, falling between 80% and 120% of prescribed dose. For 5 of the implants, D90 is less than 90%, but only 2 out of the 5 achieved the V150 target. All the implants met the target dose for rectum: V1001.3cc. Conclusion: The fact that majority of the implants failed to meet V150 target, but met both the D30 and D5 for urethra implies that V150 is not an accurate surrogate of urethra dose or acute morbidity. This study shows that in an effort to improve quality of life while achieving a survival benefit, it may be more important to accurately delineate the urethra, and report D30, D5 in post-implant analysis. Continued clinical study is needed to evaluate whether D30 and D5 can better predict urinary complications. Author Disclosure: C. Yan: None.
Management of Prostate Cancer Using Magnetic Resonance Guided Pulsed Focused Ultrasound-Mediated Targeted Chemotherapeutic Agent Delivery L. Chen, D. Cvetkovic, B. Wang, R. Gupta, and C.M.C. Ma; Fox Chase Cancer Center, Philadelphia, PA Purpose/Objective(s): The purpose of this study is to investigate an approach to prostate cancer therapy using nanodroplet-encapsulated drugs combined with pulsed high intensity focused ultrasound (pFUS) treatment. Materials/Methods: Human prostate tumor (LNCaP) cells were implanted into the prostates of nude mice. Tumor growth was monitored using MRI. When tumor volumes reached 140 10 mm3 on MRI, the tumorebearing mice were randomly divided into 5 groups (n Z 5 for each group). Group 1, animals were treated with an IV injection of docetaxel-encapsulated nanodroplets (ND-DTX) + pFUS. Animals in Group 2 were treated with pFUS alone. Animals in Group 3 were injected (IV) with DTX-encapsulated nanodroplets alone, Group 4 received free DTX alone and Group 5 was used as a control group. The formulation of the DTX-encapsulated nanodroplets was: DTX dose 20 mg/kg, Nanoemulsion composition 0.5% PTX, 1% perfluorocarbon and 2% stabilizing block copolymer. The MRgFUS treatment was performed on a clinical HIFU (high intensity focused ultrasound) device (ExAblate 2000, InSightec-Tx-Sonics, Haifa, Israel, and Dallas, TX) together with a 1.5 T GE MR scanner. During the animal treatment, phase MR images were used for the temperature measurement in the treatment target. The MRgFUS system was capable of both treatment planning and treatment monitoring in near real-time (with a 3 second delay). After treatment, animals were allowed to survive for 3 weeks. Tumor growth delay was monitored by MRI (resolution: <0.2mm). Ultrasound treatment parameters were 1MHz, 25W acoustic power, 10% duty cycle and 60 sec for each sonication. Multiple treatment spots (8-12) were used to cover the whole tumor depending on the individual tumor sizes. Results: Using our focused ultrasound treatment protocol described above the temperature elevation was less than 5 C in the treatment volume for all animals treated resulting in absolute temperature of less than 42 C after general anesthesia. The time for the entire MRgFUS treatment procedure was approximately 1 hour including animal anesthesia and treatment setup. All animals tolerated the ultrasound treatment well. Our study results showed that group 1, in which animals were treated with an IV injection of docetaxel-encapsulated nanodroplets (ND-DTX) + pFUS, exhibited the most tumor growth delay (50% - 30%) among all groups. All other groups showed similar tumor growth to that of the control group after the treatment (within statistical uncertainties). Conclusion: Our preliminary results showed a great potential for prostate cancer therapy using targeted DTX+ nanodroplets, which could be activated by pFUS. Further animal studies are warranted to confirm the results quantitatively. The mechanisms of the treatment effect are being studied histologically. Author Disclosure: L. Chen: None. D. Cvetkovic: None. B. Wang: None. R. Gupta: None. C. Ma: None.
2633 Radium-223 in Metastatic CastrationeResistant Prostate Cancer: Single-Institution Analysis of Factors Associated With Treatment Completion and Survival A. Bang,1 S. Malone,1 E.Y.C. Leung,2 C. Canil,1 L. Eapen,1 and S.C. Morgan1; 1The Ottawa Hospital Cancer Centre, Ottawa, ON, Canada, 2The Ottawa Hospital, Ottawa, ON, Canada Purpose/Objective(s): Radium-223 (Ra-223), an alpha particle-emitting radionuclide, is the first bone-targeted therapy demonstrated to improve survival in metastatic castration-resistant prostate cancer (mCRPC). We report our institution’s experience, exploring the association between mCRPC therapies received prior to Ra-223 and treatment outcomes.
Volume 96 Number 2S Supplement 2016 Materials/Methods: The outcomes of patients with progressive, symptomatic mCRPC with bone metastases treated with Ra-223 between Oct. 2009 and Dec. 2015 were analyzed. The association between baseline characteristics and outcomes were analyzed using descriptive statistics while overall survival (OS) was estimated using the Kaplan-Meier method. Toxicities were assessed using NCI CTCAE v4.0. Results: A total of 36 patients were analyzed. Median follow-up was 6.8 months (range, 1.5-34.7). Median age was 75 years (range, 49-88). Prior to commencing Ra-223, 14 patients (39%) were treated with abiraterone acetate (abi), 17 patients (47%) with enzalutamide (enza), and 14 patients (39%) with docetaxel; 16 patients (44%) received more than one agent and 7 (19%) received none. The median number of Ra-223 injections received was 5 (range, 1-6). Nineteen patients (53%) discontinued therapy prematurely. Median OS for the total cohort was 10.0 months (95% CI, 4.5-15.0). There was a non-significant trend towards shorter OS in those patients that had received prior abi or enza vs. those that had received neither of these agents (median 6.8 vs. 14.0 months; HR 2.67; 95% CI, 0.87-8.20; log-rank P Z 0.087). Forty-four percent of patients who received prior abi/enza completed all 6 planned injections vs. 55% of those that did not. There were differences seen in the baseline characteristics of these two groups: mean PSA 272 vs. 114 mcg/L, and proportion with 20 metastases 64% vs. 44%, respectively. Cumulative incidence of grade 3 hematologic toxicity during or after treatment was as follows: anemia 19%, neutropenia 0%, and thrombocytopenia 11%. Conclusion: This cohort of patients receiving Ra-223 spans the era prior to the advent of abi and enza and thus included patients with and without prior exposure to these agents. Patients receiving these agents prior to commencing Ra-223 were less likely to complete the 6 planned injections, and had a non-significant trend toward shorter survival, raising the hypothesis that earlier integration of Ra-223 in the mCRPC disease course may be preferred. This apparent association may reflect greater disease burden in more heavily pre-treated patients, rather than diminished efficacy of Ra-223. Finally, the toxicity profile of Ra-223 observed in this realworld setting was relatively favorable and comparable to that seen in the phase III trial that led to regulatory approval. Author Disclosure: A. Bang: None. S. Malone: Independent Contractor; The Ottawa Hospital. E.Y. Leung: Independent Contractor; The Ottawa Hospital. C. Canil: Independent Contractor; The Ottawa Hospital. L. Eapen: Independent Contractor; The Ottawa Hospital. S.C. Morgan: Independent Contractor; The Ottawa Hospital.
2634 Stereotactic Body Radiation Therapy to the Prostate: Patterns of Care in the National Cancer Data Base J.P. Weiner,1,2 D. Schwartz,1,2 M. Shao,1,2 V. Osborn,1,2 and D. Schreiber1,2; 1SUNY Downstate Medical Center, Brooklyn, NY, 2 Veterans Affairs NY Harbor Healthcare System, Brooklyn, NY Purpose/Objective(s): To analyze the utilization and patterns of care of stereotactic body radiation therapy (SBRT) in the treatment of prostate cancer. Materials/Methods: Men who were diagnosed with localized prostate cancer between 2004 and 2012 and treated with radiation therapy were included. Men were categorized as receiving external beam radiation, prostate brachytherapy, or SBRT to the prostate or pelvis. Descriptive statistics were used to analyze stereotactic radiation therapy usage and compared via Chi Square or Fisher’s Exact Test. Results: There were 299,186 patients identified, of which 5,078 (1.7%) were identified as receiving SBRT. Of those, 2,108 had low risk disease (41.5%), 2,251 had intermediate risk disease (44.3%) and 719 had high risk disease (14.2%). The relative utilization of SBRT increased from 0.1% in 2004 to 4.0% in 2012 (P<0.001). The relative utilization over time increased more rapidly in academic programs from 0.1% in 2004 to 7.1% of all patients receiving radiation in 2012 (P<0.001). In non-academic programs, there was a slower increase in utilization from 0.1% in 2004 to 2.6% in 2012. The most commonly utilized fractionation scheme included
Poster Viewing E261 5 fractions in 4,635 patients (91.3%), with 725 cGy x 5 the most common fractionation scheme (49.6%) followed by 700 cGy x 5 (21.3%). Doses of 750 cGy per day were more commonly utilized in non-academic centers (32.3%) compared to academic centers (26.1%). Conclusion: SBRT is slowly increasing acceptance, but more so in academic facilities. 700-725 cGy x 5 fractions appears to be the most commonly utilized fractionation scheme. As further long-term data regarding the safety and efficacy emerges, the relative utilization of SBRT is expected to continue to increase. Author Disclosure: J.P. Weiner: None. D. Schwartz: None. M. Shao: None. V. Osborn: None. D. Schreiber: None.
2635 Vector Analysis of Bladder Cancer Patient Setup Utilizing a Magnetic Resonance Image Guided Radiation Therapy (MR-IGRT) System B.W. Fischer-Valuck, O.L. Green, S. Mutic, H.A. Gay, and J.M. Michalski; Washington University School of Medicine, St. Louis, MO Purpose/Objective(s): Inter and intra-fraction anatomy changes in patients undergoing radiation therapy (RT) for bladder cancer (BC) are common but have thus far been studied with implanted fiducial markers, limited quality 2-D orthogonal films and computed tomography (CT). The adverse impact of daily set-up variation could be more significant than appreciated. Our goal was to employ the soft tissue imaging capabilities of an integrated magnetic resonance image-guided RT (MR-IGRT) system to analyze daily positioning. Materials/Methods: Fourteen patients with BC were treated on a MRIGRT system. Patient setup was performed via volumetric MR imaging with a resolution of 0.15 x 0.15 cm. Alignment was performed according to skin marks then shifts assessed by comparing the treatment volume from the planning CT to the daily MR image. Two hundred forty pretreatment MR images were analyzed and 3 shifts were recorded for each image. A vector shift was calculated by combining the square root of the combined sum of the shifts squared. Number of times that the vector of combined shifts would have exceeded the planning tumor volume (PTV) was recorded. Results: The daily volumetric MR imaging allowed for accurate alignment and daily monitoring of bladder volume and normal tissue anatomy. Recorded shifts of the treated volume were 0.90.5 cm in the right/left direction, 0.70.3 cm in the anterior/posterior direction, and 0.70.4 cm in the cranio-caudal direction. In 66 (28%) of cases the vector shift was initially greater than the PTV margin. For 2 patients, pre-treatment MR imaging revealed the tumor reduced in size and dose to the bowel would have exceeded constraints, and treatment adaptation was performed to reduce normal tissue toxicity. Using CTCAE criteria, no grade 3 or higher toxicities have been reported. Conclusion: Accurate and reproducible treatment delivery is required to avoid marginal misses to the target volume as well as excess dose to normal tissue. MR-IGRT allows for excellent soft tissue visualization which enables for the avoidance of potential setups errors by allowing daily alignment changes to ensure the target is included in the PTV. It also allows the ability to make treatment changes based on anatomy variations. Author Disclosure: B.W. Fischer-Valuck: None. O.L. Green: Honoraria; ViewRay. S. Mutic: Research Grant; ViewRay. Honoraria; ViewRay. Consultant; ViewRay. Advisory Board; ViewRay. Travel Expenses; ViewRay. Stock; ViewRay. Royalty; ViewRay. H.A. Gay: None. J.M. Michalski: None.
2636 The Effect of Lovastatin on Preservation of Erectile Function After Radiation Therapy (RT) for Prostate Cancer: Secondary Analysis of a Prospective Study M.S. Anscher,1 M.G. Chang,2 D. Moghanaki,3 M. Rosu,4 R.B. Mikkelsen,4 D. Holdford,5 V. Skinner,6 B.M. Grob,1 A. Sanyal,1