- Email: [email protected]
Initial Outcome of Definitive Intensity Modulated Radiation Therapy in Treatment of Bone Oligometastatic Prostate Cancer
E272
International Journal of Radiation Oncology Biology Physics
Sinai, New York, NY, 2H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL
Results: The mean age was 69.2 years [58-76]. At the time of follow-up, there was no biochemical relapse. Before RT, the mean IIEF5 score in all 13 patients was 23.4 [20-25]. At 6, 12 and 24 months after RT, the IIEF scores were 19.5 [5-25], 18.8 [5-25] and 20.3 [6-25], respectively. At two years, 8 patients (61.5%) had no ED and 2 patients (13.3%) experienced a mild ED. The mean reduction of the IIEF5 score was 3.15. Among the 3 patients with important ED, 2 had a medical treatment (Sildenafil Citrate) and recovered a satisfactory IIEF score at 22 and 24. Conclusion: The primary results of this technique of optimization for sexual preservation are encouraging. Despite a mean age close to 70 years at the time of treatment, almost 75% of the patients had no to mild sexual dysfunction at two years. This rate increases at 92% with the use of Sildenafil Citrate. Author Disclosure: H. Samlali: None. C. Udrescu: None. C. Enachescu: None. S. Yossi: None. A. Lapierre: None. P. Jalade: None. O. Chapet: speaker; IPSEN, TAKEDA. Board Member; Astellas.
Purpose/Objective(s): The hypothesis is that fiducial marker based 2D kV orthogonal imaging (kV+FM) and soft-tissue (ST) based cone beam computed tomography (CBCT) are equally reliable imaging modalities for daily positional alignments for image-guided (IG) intensity-modulated radiation therapy (IMRT) for prostate cancer. Materials/Methods: Ten patients undergoing treatment for prostate cancer with IG-IMRT, total dose of 7560 cGy over 42 treatments, were imaged daily with kV+FM and CBCT-ST. Offline alignments to the planning CT were made twice for each kV and CBCT acquired image in order to determine the test-retest reliability in making daily alignments for each modality. Results: kV+FM demonstrated better intraobserver test-retest reliability in the anterior-posterior (AP) (Pearson correlation coefficient (r) 95% confidence interval (CI) Z 0.987-0.991), right-left (RL) (r 95% CI Z 0.9850.990), and superior-inferior (SI) (r 95% CI Z 0.970-0.980) directions when adjusting for interfractional shifts compared to CBCT-ST (AP: r 95% CI Z 0.804-0.877; RL: r 95% CI Z 0.877-0.924; SI: r 95% CI Z 0.7910.869). Error associated with intraobserver test-retest reliability was submillimeter with kV+FM in all directions (AP 0.42+/-0.71 mm; RL 0.37+/0.49 mm; SI 0.46+/-0.66 mm) compared to CBCT-ST (AP: 2.06+/-2.21 mm; RL: 1.33+/-1.43 mm; SI: 1.20+/-1.78 mm). The error introduced by test-retest variability with CBCT-ST indicates a need for larger target margins in all directions (AP Z 4.8 mm, RL Z 5.4 mm, SI Z 9.5 mm) using Van Herk’s formula (margin Z 2.5*S + 0.7*s) if one makes the assumption that the more reproducible imaging modality, kV+FM, identifies the true isocenter. In order to assess how the error associated with test-retest variability for CBCT-ST affects the dose distribution, dosevolume histograms (DVHs) were generated using these expanded margins. In addition, plans were generated using the standard 5 mm margins with isocenters shifted posteriorly by 0.5, 1 and 2 standard deviations of the observed posterior variability of soft tissue CBCT, i.e. 1.1, 2.2 and 4.4 mm, respectively, simulating an example of the impact of such misalignments. DVHs generated from these plans indicate that the poor test-retest reliability associated with CBCT-ST imaging for interfractional shifts could result in a substantial increase in dose to healthy tissue, particularly the rectum, and decreased dose to the prostate, in many patients. Conclusion: Use of kV+FM compared to CBCT-ST imaging for IG-IMRT is more reliable for daily alignments and may permit the safe and effective use of smaller margins in order to reduce the radiation exposure to healthy tissue in patients treated for prostate cancer. Tight margins should be used cautiously in patients aligned with soft tissue CBCT. Author Disclosure: P.H. Goff: None. L.B. Harrison: None. E.E. Furhang: None. F. Trichter: None. R.D. Ennis: None.
2662 Prospective Evaluation of a Specific Technique of Sexual Function Preservation in External Beam Radiation Therapy for Prostate Cancer H. Samlali, C. Udrescu, C. Enachescu, S. Yossi, A. Lapierre, P. Jalade, and O. Chapet; Centre Hospitalier Lyon Sud, Lyon, France Purpose/Objective(s): Sexual preservation is an important issue in the treatment of localized prostate cancer. A specific technique of irradiation was developed to better preserve this function and has been evaluated. Materials/Methods: Between 2010 and 2014, 13 patients, with no erectile dysfunction (ED), were treated with intensity-modulated radiation therapy (total dose: 74-78Gy, 2Gy/fraction) and daily set-up on 3 intra-prostatic gold markers (for a low- or intermediate-risk prostate cancer). The pudendal arteries, penile bulb and cavernous body were delineated on the planning CT scan. The doses to these structures (with a 5 mm margin) were optimized to be as low as possible. The erectile function (EF) was documented using IIEF-5 (International Index of Erectile Function) scores at baseline (before RT), 6 months, 1 year and 2 years. No erectile dysfunction was defined by an IIEF-5 >20/25, a mild ED by an IIEF-5 score of 17-19 and an important ED by a score<17.
2663 Infections After Fiducial Markers Implantation for Prostate Radiation Therapy: Optimizing the Antimicrobial Prophylaxis S. Clavel, A.S. Gauthier-Pare, D. Duplan, J. Fanizzi, N. Rivest, and O. Haeck; Hopital de la Cite-de-la-Sante, Laval, QC, Canada Purpose/Objective(s): The use of fiducial markers for prostate imageguided radiation therapy is a common practice. Published literature suggests rates of infection between 1 and 7% following this procedure. We evaluated the tolerability of the procedure and the relationships between two antimicrobial prophylaxis protocols and the incidence of post-implant infections Materials/Methods: Between 2011 and 2015, 317 patients with localized prostate cancer had implantation of 3-4 intraprostatic fiducial markers under transrectal ultrasound guidance in our center. Patients received standard oral fluoroquinolone (Ciprofloxacin) antibiotic prophylaxis for 3 doses until June 2014. Afterward, based on the rates and types of infections observed and recommendations from our Department of Microbiology, the protocol was changed to oral Ciprofloxacin for 1 dose and Fosfomycin Tromethamin for one dose, 2 hours before procedure. Toxicities during installation and urinary infectious events were confirmed through medical records of patients that were seen for treatment planning 1-2 weeks after implantation and every 2 weeks during radiation treatment. All urinary tract infections within 45 days of procedure were considered to be procedure-related. Results: There were 3 interruptions of the implantation secondary to pain and no interruption related to hemorrhage. A total of 208 patients were identified in the Ciprofloxacin alone cohort and 109 in the Ciprofloxacin +Fosfomycin cohort. The post-implant infection rate was 4.3% (9 patients) in the Ciprofloxacin group vs. 0.9% (1 patients) in the Ciprofloxacin and Fosfomycin group (Fisher P Z 0.17). Gleason score, prostate cancer risk group, prostate size and number of markers installed were well balanced between groups and were not found to be independent predictors of infection. Conclusion: Transrectal fiducial markers implantation for image-guided radiation therapy in prostate cancer is a well-tolerated procedure. Our results suggest a trend for a reduction in infection rates following markers implantation with prophylactic Ciprofloxacin and Fosfomycin compared to Ciprofloxacin alone. Statistical significance was likely not achieved due to a low number of events. Further studies/follow-up is required to recommend an optimal regimen. Author Disclosure: S. Clavel: None. A. Gauthier-Pare: None. D. Duplan: None. J. Fanizzi: None. N. Rivest: None. O. Haeck: None.
2664 Initial Outcome of Definitive Intensity Modulated Radiation Therapy in Treatment of Bone Oligometastatic Prostate Cancer X. Qi, X.S. Gao, H. Li, S.B. Qin, M. Zhang, X.M. Li, X. Li, and M. Ma; Department of Radiation Oncology, Peking University First Hospital, Beijing, China
Volume 96 Number 2S Supplement 2016 Purpose/Objective(s): The aim of this study was to evaluate the PSA response rate, biochemical relapse-free survival, and toxicity in bone oligometastatic prostate cancer patients who had undergone definitive intensity modulated radiation therapy (IMRT) for both primary tumor and all metastatic lesions. Materials/Methods: From 10/2011 to 9/2015, 22 prostate cancer patients with bone oligometastases (no more than 5 metastatic lesions) were treated. Metastatic lesions were documented by positive bone scan or CT scan or MRI. All patients received IMRT, 40-76Gy in 10-38 fractions (median dose: 60Gy) to metastatic lesions, 45-46Gy to the whole pelvis (for 14 patients, 63.6%) and 72-76Gy to the prostate and seminal vesicles. All patients received MAB using a LHRH agonist or orchiectomy together with an oral anti-androgen before and during RT. After RT, all patients received continuous ADT except one due to cardiovascular disease. Survival was calculated using the Kaplan-Meier method. Results: A total of 49 bone metastatic lesions were identified in these 22 patients. The median number of metastatic lesions per patient was 2 (range 1-5). Twenty-nine (59.1%) lesions were localized in the pelvis, 14 (28.6%) in the spines, 3 (6.1%) in the femurs and 3 (6.1%) in the ribs. The median follow-up was 17 months (range: 2-48 months). The median duration of ADT before RT was 5 months and the median pre-RT PSA was 0.7ng/ml. PSA response rate: 20 patients had a PSA decline 2 months after RT, and 13 of them decreased to <0.1ng/ml (59.1%). The rate of biochemical relapse-free survival (bRFS) rates at 1-year and 2-year based on the nadir plus 2 ng/mL definition were 85.7% and 71.4%, respectively. Three patients had biochemical failure at 2, 13, and 24 months after RT, respectively. They all received the second line ADT and one of them developed lung metastases after 23 months of ADT. Additionally, no acute or late grade 3/4 GI or GU toxicity was recorded. Conclusion: Our study suggests that definitive IMRT is well tolerated and results in good PSA response and biochemical control in patient with bone oligometastatic prostate cancer. However, the long-term survival outcomes need to be further explored. Author Disclosure: X. Qi: None. X. Gao: None. H. Li: None. S. Qin: None. M. Zhang: None. X. Li: None. X. Li: None. M. Ma: None.
2665 Meeting Dose Objectives in Stereotactic Body Radiation Therapy for Prostate Cancer: Water- Versus Air-Filled Endorectal Balloon? L. Tsvang,1 A. Dubouloz,2 D. Alezra,3 Z. Symon,3 and R. Miralbell2; 1 Chaim Sheba Medical Center, Ramat Gan, Israel, 2Radiation Oncology, Hopitaux Universitaires de Geneve (HUG), Geneva, Switzerland, 3 Radiation Oncology, Sheba Medical Center, Tel Hashomer, Israel Purpose/Objective(s): To compare the achievement and cost of dose objectives defined for a European multicenter phase II trial of urethrasparing SBRT using water vs. air-filled endorectal balloon (ERB). Materials/Methods: Ten patients simulated with a 100cc filled ERB for prostate SBRT were analyzed. Hounsfield units in the balloon were adjusted for comparison of air and water. Prescription dose to the PTV was 36.25 Gy in 5 fractions of 7.25 Gy. The urethral dose prescription (urethral planning risk volume, uPRV) was 32.5 Gy. Treatment plans were optimized using volumetric intensity-modulated arc treatment (VMAT) technique and dose was delivered with two arcs. We hypothesized that the optimization algorithm would perform better with water-filled EBR vs. air due to homogeneity of tissue density. Thus, two optimizations were run for each air-filled balloon: one with the same objective template as water and a second improved optimization (IO) which drives improved PTV coverage. The plans were compared for following parameters according to the research protocol: PTV98%, PTV95%, PTV2%, PTV-Rectal wall intersection PTV-R 98%, PTV-R2%, PTV-Rmean, RwallDmax, Rwall100%, Rwall90%, Rwall80%, Homogeneity Index HI PTV-R. Results: The goal of PTV98% covered by the 95% prescription dose was achieved for all water-filled ERB and only 60% of air-filled ERB (P Z 0.02, chi2). Improved optimization (IO) for air achieved the goal in 80% of
Poster Viewing E273 air-filled ERB. The PTV-R98% (representing overlap of anterior rectal wall and PTV) dose coverage was significantly less for air vs. water: 89.1% 1.6 vs. 94.4%1.6 (P<0.0001), but increased to 94.3%1.8 with IO. The rectal volume Rwall100% was 0.25cc 0.16 vs. 1.87cc 0.69 for air vs. water (P<0.0002), however increases to 1.27cc 0.67 for IO. Conclusion: Water-filled ERB provide superior PTV coverage than air at the cost of exposing a greater volume of rectal tissue to doses above 100% of the prescription dose. Strategies to improve PTV coverage for air-filled ERB succeed in most patients, yet will increase dose to the anterior rectal wall. The clinical impact of exposing minute volumes of rectal wall to ultra-high doses is unknown and will be clinically correlated with longer follow-up of patients treated in this protocol. Author Disclosure: L. Tsvang: None. A. Dubouloz: None. D. Alezra: None. Z. Symon: None. R. Miralbell: None.
2666 Intermediate-Risk Prostate Cancer Treated With 3 Radioablative Regimens: Comparison of Robotic Ultrahypofractionation and High-Dose-Rate Brachytherapy Alone or Combined With External Beam Radiation Therapy P.A. Wojcieszek, M. Szlag, G. Glowacki, A. Cholewka, M. Fijalkowski, S. Kellas, B. Biala, and L. Miszczyk; MSC Memorial Cancer Center and Institute of Oncology, Gliwice Branch, Gliwice, Poland Purpose/Objective(s): Evaluation of the morbidity and the outcomes among the intermediate-risk prostate cancer patients treated with three radiation therapy regimens using radioablative doses per fraction (>7Gy). Materials/Methods: One hundred eighty-three intermediate-risk prostate cancer patients were treated in the three prospective trials on the robotic ultrahypofractionation (RUH), the high-dose-rate brachytherapy alone (HDRalone) and the external-beam radiation therapy combined with the high-dose-rate boost (HDRboost). The regimens were 5x7.25Gy, 3x11Gy and 23-25x2Gy+1-2x10-10.5Gy for RUH, HDRalone and HDRboost, respectively. To minimize disparity the outcome blinded adjusting (i.e. 1:1:1 matching with following criteria: Gleason score, maximum PSA, T stage, age) was performed on the patients, who exceeded the follow-up of 6 months. Each group included 29 patients to total number of 87 patients enrolled into this study. Wilcoxon and Kruskal-Wallis tests were used to assess the differences among the groups. Kaplan-Meier analysis and logrank test were used to estimate the survival. Results: There were statistically significant differences between the groups. RUH had the highest maximal PSA (P-.0000), HDRboost had the highest T stage (P-.03), and both HDR groups had higher Gleason scores (P-.009). Median follow-up for RUH, HDRalone and HDRboost was 19, 16 and 36 months, respectively. HDRboost and RUH were significantly linked with mild gastrointestinal morbidity (P-.02). There were no differences between PSA levels between the groups at the last follow-up. Biochemical disease-free survival at 2 years was better for both HDR groups than RUH (100% vs 96%; P-0.09), however it was not significant. Conclusion: Regimens using radioablative doses per fraction are efficient, while yielding low morbidity. In spite of the necessity of the long-term results, comparison with conventional and/or hypofractionated externalbeam radiation therapy schedules should be performed with further randomized clinical trial design. Author Disclosure: P.A. Wojcieszek: None. M. Szlag: None. G. Glowacki: None. A. Cholewka: None. M. Fijalkowski: None. S. Kellas: None. B. Biala: None. L. Miszczyk: None.
2667 Outcomes and Toxicity for Treatment of Adrenal Metastases With Radiation Therapy W.G.A. Wang,1 K. Sura,1 J. Robertson,1 D.J. Krauss,1 P.Y. Chen,2 and I.S. Grills2; 1Beaumont Health, Royal Oak, MI, 2Beaumont Health System, Royal Oak, MI
International Journal of Radiation Oncology Biology Physics
Sinai, New York, NY, 2H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL
Results: The mean age was 69.2 years [58-76]. At the time of follow-up, there was no biochemical relapse. Before RT, the mean IIEF5 score in all 13 patients was 23.4 [20-25]. At 6, 12 and 24 months after RT, the IIEF scores were 19.5 [5-25], 18.8 [5-25] and 20.3 [6-25], respectively. At two years, 8 patients (61.5%) had no ED and 2 patients (13.3%) experienced a mild ED. The mean reduction of the IIEF5 score was 3.15. Among the 3 patients with important ED, 2 had a medical treatment (Sildenafil Citrate) and recovered a satisfactory IIEF score at 22 and 24. Conclusion: The primary results of this technique of optimization for sexual preservation are encouraging. Despite a mean age close to 70 years at the time of treatment, almost 75% of the patients had no to mild sexual dysfunction at two years. This rate increases at 92% with the use of Sildenafil Citrate. Author Disclosure: H. Samlali: None. C. Udrescu: None. C. Enachescu: None. S. Yossi: None. A. Lapierre: None. P. Jalade: None. O. Chapet: speaker; IPSEN, TAKEDA. Board Member; Astellas.
Purpose/Objective(s): The hypothesis is that fiducial marker based 2D kV orthogonal imaging (kV+FM) and soft-tissue (ST) based cone beam computed tomography (CBCT) are equally reliable imaging modalities for daily positional alignments for image-guided (IG) intensity-modulated radiation therapy (IMRT) for prostate cancer. Materials/Methods: Ten patients undergoing treatment for prostate cancer with IG-IMRT, total dose of 7560 cGy over 42 treatments, were imaged daily with kV+FM and CBCT-ST. Offline alignments to the planning CT were made twice for each kV and CBCT acquired image in order to determine the test-retest reliability in making daily alignments for each modality. Results: kV+FM demonstrated better intraobserver test-retest reliability in the anterior-posterior (AP) (Pearson correlation coefficient (r) 95% confidence interval (CI) Z 0.987-0.991), right-left (RL) (r 95% CI Z 0.9850.990), and superior-inferior (SI) (r 95% CI Z 0.970-0.980) directions when adjusting for interfractional shifts compared to CBCT-ST (AP: r 95% CI Z 0.804-0.877; RL: r 95% CI Z 0.877-0.924; SI: r 95% CI Z 0.7910.869). Error associated with intraobserver test-retest reliability was submillimeter with kV+FM in all directions (AP 0.42+/-0.71 mm; RL 0.37+/0.49 mm; SI 0.46+/-0.66 mm) compared to CBCT-ST (AP: 2.06+/-2.21 mm; RL: 1.33+/-1.43 mm; SI: 1.20+/-1.78 mm). The error introduced by test-retest variability with CBCT-ST indicates a need for larger target margins in all directions (AP Z 4.8 mm, RL Z 5.4 mm, SI Z 9.5 mm) using Van Herk’s formula (margin Z 2.5*S + 0.7*s) if one makes the assumption that the more reproducible imaging modality, kV+FM, identifies the true isocenter. In order to assess how the error associated with test-retest variability for CBCT-ST affects the dose distribution, dosevolume histograms (DVHs) were generated using these expanded margins. In addition, plans were generated using the standard 5 mm margins with isocenters shifted posteriorly by 0.5, 1 and 2 standard deviations of the observed posterior variability of soft tissue CBCT, i.e. 1.1, 2.2 and 4.4 mm, respectively, simulating an example of the impact of such misalignments. DVHs generated from these plans indicate that the poor test-retest reliability associated with CBCT-ST imaging for interfractional shifts could result in a substantial increase in dose to healthy tissue, particularly the rectum, and decreased dose to the prostate, in many patients. Conclusion: Use of kV+FM compared to CBCT-ST imaging for IG-IMRT is more reliable for daily alignments and may permit the safe and effective use of smaller margins in order to reduce the radiation exposure to healthy tissue in patients treated for prostate cancer. Tight margins should be used cautiously in patients aligned with soft tissue CBCT. Author Disclosure: P.H. Goff: None. L.B. Harrison: None. E.E. Furhang: None. F. Trichter: None. R.D. Ennis: None.
2662 Prospective Evaluation of a Specific Technique of Sexual Function Preservation in External Beam Radiation Therapy for Prostate Cancer H. Samlali, C. Udrescu, C. Enachescu, S. Yossi, A. Lapierre, P. Jalade, and O. Chapet; Centre Hospitalier Lyon Sud, Lyon, France Purpose/Objective(s): Sexual preservation is an important issue in the treatment of localized prostate cancer. A specific technique of irradiation was developed to better preserve this function and has been evaluated. Materials/Methods: Between 2010 and 2014, 13 patients, with no erectile dysfunction (ED), were treated with intensity-modulated radiation therapy (total dose: 74-78Gy, 2Gy/fraction) and daily set-up on 3 intra-prostatic gold markers (for a low- or intermediate-risk prostate cancer). The pudendal arteries, penile bulb and cavernous body were delineated on the planning CT scan. The doses to these structures (with a 5 mm margin) were optimized to be as low as possible. The erectile function (EF) was documented using IIEF-5 (International Index of Erectile Function) scores at baseline (before RT), 6 months, 1 year and 2 years. No erectile dysfunction was defined by an IIEF-5 >20/25, a mild ED by an IIEF-5 score of 17-19 and an important ED by a score<17.
2663 Infections After Fiducial Markers Implantation for Prostate Radiation Therapy: Optimizing the Antimicrobial Prophylaxis S. Clavel, A.S. Gauthier-Pare, D. Duplan, J. Fanizzi, N. Rivest, and O. Haeck; Hopital de la Cite-de-la-Sante, Laval, QC, Canada Purpose/Objective(s): The use of fiducial markers for prostate imageguided radiation therapy is a common practice. Published literature suggests rates of infection between 1 and 7% following this procedure. We evaluated the tolerability of the procedure and the relationships between two antimicrobial prophylaxis protocols and the incidence of post-implant infections Materials/Methods: Between 2011 and 2015, 317 patients with localized prostate cancer had implantation of 3-4 intraprostatic fiducial markers under transrectal ultrasound guidance in our center. Patients received standard oral fluoroquinolone (Ciprofloxacin) antibiotic prophylaxis for 3 doses until June 2014. Afterward, based on the rates and types of infections observed and recommendations from our Department of Microbiology, the protocol was changed to oral Ciprofloxacin for 1 dose and Fosfomycin Tromethamin for one dose, 2 hours before procedure. Toxicities during installation and urinary infectious events were confirmed through medical records of patients that were seen for treatment planning 1-2 weeks after implantation and every 2 weeks during radiation treatment. All urinary tract infections within 45 days of procedure were considered to be procedure-related. Results: There were 3 interruptions of the implantation secondary to pain and no interruption related to hemorrhage. A total of 208 patients were identified in the Ciprofloxacin alone cohort and 109 in the Ciprofloxacin +Fosfomycin cohort. The post-implant infection rate was 4.3% (9 patients) in the Ciprofloxacin group vs. 0.9% (1 patients) in the Ciprofloxacin and Fosfomycin group (Fisher P Z 0.17). Gleason score, prostate cancer risk group, prostate size and number of markers installed were well balanced between groups and were not found to be independent predictors of infection. Conclusion: Transrectal fiducial markers implantation for image-guided radiation therapy in prostate cancer is a well-tolerated procedure. Our results suggest a trend for a reduction in infection rates following markers implantation with prophylactic Ciprofloxacin and Fosfomycin compared to Ciprofloxacin alone. Statistical significance was likely not achieved due to a low number of events. Further studies/follow-up is required to recommend an optimal regimen. Author Disclosure: S. Clavel: None. A. Gauthier-Pare: None. D. Duplan: None. J. Fanizzi: None. N. Rivest: None. O. Haeck: None.
2664 Initial Outcome of Definitive Intensity Modulated Radiation Therapy in Treatment of Bone Oligometastatic Prostate Cancer X. Qi, X.S. Gao, H. Li, S.B. Qin, M. Zhang, X.M. Li, X. Li, and M. Ma; Department of Radiation Oncology, Peking University First Hospital, Beijing, China
Volume 96 Number 2S Supplement 2016 Purpose/Objective(s): The aim of this study was to evaluate the PSA response rate, biochemical relapse-free survival, and toxicity in bone oligometastatic prostate cancer patients who had undergone definitive intensity modulated radiation therapy (IMRT) for both primary tumor and all metastatic lesions. Materials/Methods: From 10/2011 to 9/2015, 22 prostate cancer patients with bone oligometastases (no more than 5 metastatic lesions) were treated. Metastatic lesions were documented by positive bone scan or CT scan or MRI. All patients received IMRT, 40-76Gy in 10-38 fractions (median dose: 60Gy) to metastatic lesions, 45-46Gy to the whole pelvis (for 14 patients, 63.6%) and 72-76Gy to the prostate and seminal vesicles. All patients received MAB using a LHRH agonist or orchiectomy together with an oral anti-androgen before and during RT. After RT, all patients received continuous ADT except one due to cardiovascular disease. Survival was calculated using the Kaplan-Meier method. Results: A total of 49 bone metastatic lesions were identified in these 22 patients. The median number of metastatic lesions per patient was 2 (range 1-5). Twenty-nine (59.1%) lesions were localized in the pelvis, 14 (28.6%) in the spines, 3 (6.1%) in the femurs and 3 (6.1%) in the ribs. The median follow-up was 17 months (range: 2-48 months). The median duration of ADT before RT was 5 months and the median pre-RT PSA was 0.7ng/ml. PSA response rate: 20 patients had a PSA decline 2 months after RT, and 13 of them decreased to <0.1ng/ml (59.1%). The rate of biochemical relapse-free survival (bRFS) rates at 1-year and 2-year based on the nadir plus 2 ng/mL definition were 85.7% and 71.4%, respectively. Three patients had biochemical failure at 2, 13, and 24 months after RT, respectively. They all received the second line ADT and one of them developed lung metastases after 23 months of ADT. Additionally, no acute or late grade 3/4 GI or GU toxicity was recorded. Conclusion: Our study suggests that definitive IMRT is well tolerated and results in good PSA response and biochemical control in patient with bone oligometastatic prostate cancer. However, the long-term survival outcomes need to be further explored. Author Disclosure: X. Qi: None. X. Gao: None. H. Li: None. S. Qin: None. M. Zhang: None. X. Li: None. X. Li: None. M. Ma: None.
2665 Meeting Dose Objectives in Stereotactic Body Radiation Therapy for Prostate Cancer: Water- Versus Air-Filled Endorectal Balloon? L. Tsvang,1 A. Dubouloz,2 D. Alezra,3 Z. Symon,3 and R. Miralbell2; 1 Chaim Sheba Medical Center, Ramat Gan, Israel, 2Radiation Oncology, Hopitaux Universitaires de Geneve (HUG), Geneva, Switzerland, 3 Radiation Oncology, Sheba Medical Center, Tel Hashomer, Israel Purpose/Objective(s): To compare the achievement and cost of dose objectives defined for a European multicenter phase II trial of urethrasparing SBRT using water vs. air-filled endorectal balloon (ERB). Materials/Methods: Ten patients simulated with a 100cc filled ERB for prostate SBRT were analyzed. Hounsfield units in the balloon were adjusted for comparison of air and water. Prescription dose to the PTV was 36.25 Gy in 5 fractions of 7.25 Gy. The urethral dose prescription (urethral planning risk volume, uPRV) was 32.5 Gy. Treatment plans were optimized using volumetric intensity-modulated arc treatment (VMAT) technique and dose was delivered with two arcs. We hypothesized that the optimization algorithm would perform better with water-filled EBR vs. air due to homogeneity of tissue density. Thus, two optimizations were run for each air-filled balloon: one with the same objective template as water and a second improved optimization (IO) which drives improved PTV coverage. The plans were compared for following parameters according to the research protocol: PTV98%, PTV95%, PTV2%, PTV-Rectal wall intersection PTV-R 98%, PTV-R2%, PTV-Rmean, RwallDmax, Rwall100%, Rwall90%, Rwall80%, Homogeneity Index HI PTV-R. Results: The goal of PTV98% covered by the 95% prescription dose was achieved for all water-filled ERB and only 60% of air-filled ERB (P Z 0.02, chi2). Improved optimization (IO) for air achieved the goal in 80% of
Poster Viewing E273 air-filled ERB. The PTV-R98% (representing overlap of anterior rectal wall and PTV) dose coverage was significantly less for air vs. water: 89.1% 1.6 vs. 94.4%1.6 (P<0.0001), but increased to 94.3%1.8 with IO. The rectal volume Rwall100% was 0.25cc 0.16 vs. 1.87cc 0.69 for air vs. water (P<0.0002), however increases to 1.27cc 0.67 for IO. Conclusion: Water-filled ERB provide superior PTV coverage than air at the cost of exposing a greater volume of rectal tissue to doses above 100% of the prescription dose. Strategies to improve PTV coverage for air-filled ERB succeed in most patients, yet will increase dose to the anterior rectal wall. The clinical impact of exposing minute volumes of rectal wall to ultra-high doses is unknown and will be clinically correlated with longer follow-up of patients treated in this protocol. Author Disclosure: L. Tsvang: None. A. Dubouloz: None. D. Alezra: None. Z. Symon: None. R. Miralbell: None.
2666 Intermediate-Risk Prostate Cancer Treated With 3 Radioablative Regimens: Comparison of Robotic Ultrahypofractionation and High-Dose-Rate Brachytherapy Alone or Combined With External Beam Radiation Therapy P.A. Wojcieszek, M. Szlag, G. Glowacki, A. Cholewka, M. Fijalkowski, S. Kellas, B. Biala, and L. Miszczyk; MSC Memorial Cancer Center and Institute of Oncology, Gliwice Branch, Gliwice, Poland Purpose/Objective(s): Evaluation of the morbidity and the outcomes among the intermediate-risk prostate cancer patients treated with three radiation therapy regimens using radioablative doses per fraction (>7Gy). Materials/Methods: One hundred eighty-three intermediate-risk prostate cancer patients were treated in the three prospective trials on the robotic ultrahypofractionation (RUH), the high-dose-rate brachytherapy alone (HDRalone) and the external-beam radiation therapy combined with the high-dose-rate boost (HDRboost). The regimens were 5x7.25Gy, 3x11Gy and 23-25x2Gy+1-2x10-10.5Gy for RUH, HDRalone and HDRboost, respectively. To minimize disparity the outcome blinded adjusting (i.e. 1:1:1 matching with following criteria: Gleason score, maximum PSA, T stage, age) was performed on the patients, who exceeded the follow-up of 6 months. Each group included 29 patients to total number of 87 patients enrolled into this study. Wilcoxon and Kruskal-Wallis tests were used to assess the differences among the groups. Kaplan-Meier analysis and logrank test were used to estimate the survival. Results: There were statistically significant differences between the groups. RUH had the highest maximal PSA (P-.0000), HDRboost had the highest T stage (P-.03), and both HDR groups had higher Gleason scores (P-.009). Median follow-up for RUH, HDRalone and HDRboost was 19, 16 and 36 months, respectively. HDRboost and RUH were significantly linked with mild gastrointestinal morbidity (P-.02). There were no differences between PSA levels between the groups at the last follow-up. Biochemical disease-free survival at 2 years was better for both HDR groups than RUH (100% vs 96%; P-0.09), however it was not significant. Conclusion: Regimens using radioablative doses per fraction are efficient, while yielding low morbidity. In spite of the necessity of the long-term results, comparison with conventional and/or hypofractionated externalbeam radiation therapy schedules should be performed with further randomized clinical trial design. Author Disclosure: P.A. Wojcieszek: None. M. Szlag: None. G. Glowacki: None. A. Cholewka: None. M. Fijalkowski: None. S. Kellas: None. B. Biala: None. L. Miszczyk: None.
2667 Outcomes and Toxicity for Treatment of Adrenal Metastases With Radiation Therapy W.G.A. Wang,1 K. Sura,1 J. Robertson,1 D.J. Krauss,1 P.Y. Chen,2 and I.S. Grills2; 1Beaumont Health, Royal Oak, MI, 2Beaumont Health System, Royal Oak, MI