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Multicenter Assessment of Stereotactic Body Radiation Therapy (SBRT) Boost in Intermediate-Risk Prostate Cancer: Biochemical Failure and Toxicity
Volume 96 Number 2S Supplement 2016 There were no differences in the D90 or V100 of the whole prostate, midgland or base when calculated by MRI only dosimetry compared to CTMRI fusion (P >0.19), but prostate apex D90 was 13% higher when calculated by MRI alone (P Z 0.034). In both methods the D90 and V100 of the base of the prostate gland was reduced 22% compared to the prostate apex and mid-gland. Conclusion: Post-implant MRI only based dosimetry with positive contrast, brachytherapy strand MRI markers is reliable and provides dosimetric values equivalent to CT-MRI fusion, reducing the need for postimplant CT imaging. Author Disclosure: G.V. Martin: None. T.J. Pugh: None. U. Mahmood: None. D. Swanson: None. W. Graber: None. T. Lim: None. R. Kudchadker: None. J. Wang: None. T. Bruno: None. T.K. Bathala: None. P. Blanchard: None. S.J. Frank: Chief Medical Officer, Founder; C4 Imaging. Chief Medical Officer; C4 Imaging.
2685 The Outcomes of Adjuvant Radiation Therapy in Postcystectomy Muscle-Invasive Bladder Cancer L.C. Tuanquin,1 D. McDermott,2 H.B. Mackley,2 S. Holder,2 H. Wagner, Jr,3 J.C. Rosenberg,2 J.J. Drabick,2 M. Kaag,2 M. Joshi,2 J. Raman,2 and S.B. Merrill2; 1Penn State Hershey Cancer Institute, Hershey, PA, 2Penn State Hershey Medical Center, Hershey, PA, 3Penn State Hershey Medical Center, Hershey, PA, United States Purpose/Objective(s): A current standard of care treatment for locally advanced but clinically node negative bladder cancer is radical cystectomy with neoadjuvant chemotherapy. Locoregional failure following cystectomy however remains a significant source of morbidity, and is associated with adverse pathologic features including positive surgical margins (SM+). The selection criteria for postoperative radiation therapy (PORT) and clinical effectiveness with PORT have not been well-established. The objective of this study is to evaluate clinical and pathologic features, and associated outcomes, in patients who received PORT for pT3-T4, pN0-1 M0 muscle invasive bladder cancer. Materials/Methods: The patients chosen for this retrospective review were compiled via the cancer registry at Penn State Hershey Medical Center from 1995-2015. Sixty-three patients were identified as having non-metastatic muscle invasive bladder cancer on initial presentation, who underwent cystectomy, and staged as pT3-pT4, pN0-N1. Analysis was done on a cohort of patients that received PORT with a cohort that did not. Results: Ten patients received PORT using IMRT, with one of the patients unable to complete the entire course due to toxicity, and 53 patients did not. Radiation dose ranged from 34.2-58 Gy. The PORT group had 70% urothelial histology and 60% had SM+ compared to 92% and 6%, respectively, in the non-PORT group [both statistically significant (P Z 0.038 and P Z <0.001 respectively)]. The entire cohort local recurrence (LR) rate was 28%. The PORT group had a 40% LR rate with the majority of these cases being gastrointestinal in location. The overall distant recurrence rate was 25% with no significance between the groups. The entire cohort 5-yr disease free survival (DFS) rate was 30%, and the 5-yr overall survival (OS) rate was 41%. The 5-year DFS rates were 20% in the PORT group versus 32% in the non-PORT group [not statistically significant (hazard ratio [HR] 1.498, 95% confidence interval [CI] 0.539-4.1663, log-rank P Z 0.361)]. The 5-yr OS rates were 30% in the PORT group versus 43% in the non-PORT group [not statistically significant ([HR] 0.863, [CI] 0.357-2.089, log-rank P Z 0.75)]. Multivariate analysis showed that SM+ was significant for 5-yr DFS, while nodal status and stage were significant for 5-yr OS. Conclusion: Post-cystectomy local recurrence rates were high despite the use of PORT in patients with high risk features. When considering a 5-yr OS of about 40%, reducing pelvic failure remains a critical goal. Studies evaluating the clinical target volume, radiation dose, and patterns of failure should help refine the selection criteria of patients most likely to benefit from PORT. Author Disclosure: L.C. Tuanquin: None. D. McDermott: None. H.B. Mackley: None. S. Holder: None. H. Wagner: None. J.C. Rosenberg: None. J.J. Drabick: None. M. Kaag: None. M. Joshi: None. J. Raman: None. S.B. Merrill: None.
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2686 A Dosimetric Comparison Between Conventionally Fractionated Tomotherapy, Volumetric Modulated Arc Therapy, Sliding Window and Proton Therapy, and Hypofractionated Robotic Radiosurgery Treatment by Low-Risk Prostate Carcinoma S. Scobioala,1 C. Kittel,1 U. Haverkamp,2 M. Channaoui,1 O. Habibeh,1 K. Elsayad,2 and H.T.T. Eich1; 1Radiation Oncology Department, University Hospital Muenster, Muenster, Germany, 2Department of Radiation Oncology, University Hospital Muenster, Muenster, Germany Purpose/Objective(s): Using statistical dosimetric comparison to ascertain the optimal radiation technique and fractionation regime for the treatment of low-risk prostate cancer. Materials/Methods: The treatment plans were generated from 20 randomly selected patients with low-risk prostate cancer. A dosimetric comparison was performed between a helical 3DCRT and IMRT system (HT), Sliding Window (SW), volumetric modulated arc therapy (VMAT) and protons, providing a conventional fractionation, and hypofractionated frameless robotic radiosurgery system-based stereotactic body radiation therapy (SBRT). Target doses were calculated to 79.2Gy for the conventional regime and 36.25Gy for SBRT. The dosimetric parameters for the planning target volume (PTV) and organs at risk (OAR), including a homogeneity index (HI) and four conformity indexes (CI), were comparatively analyzed. Results: The patient-averaged dose volume histogram revealed similar D98% and D2% values between techniques except for CK. HT, SW, VMAT and protons demonstrated similar HI values, which were superior to the CK homogeneity values. All techniques displayed high conformity values, with a slightly lower CI values for HT (P<.01). The dose distributions showed greater differences at low-to-medium doses than at higher doses. Protons demonstrated statistically superior rectum sparing at low-to-higher dose ranges (V10-V70, P<.01) and bladder sparing at low-to-medium doses (V10-V30, P<.01). Among the intensity-modulated approaches (IMRT), HT provided an improved rectum sparing (P<.01 versus SW and VMAT) and SW revealed superior bladder sparing (P<.01 versus HT and VMAT). CK provided superior bladder shielding at higher doses compared to other techniques (V50-V70, P<.01), and improved rectum sparing at V50 versus SW and VMAT (P<.01). Protons and CK generated significantly higher exposures of the femoral heads and HT had superior sparing of those. Conclusion: We provided a statistical dosimetric comparison between various advanced radiation techniques, comparing conventional to hypofractionated regimes in the treatment of low-risk prostate cancer. Higher homogeneity was observed for techniques applying conventional fractionation compared to CBbased SBRT. HT demonstrated slightly lower conformity than other techniques. With the exception of femoral heads, protons demonstrated significantly superior sparing of OAR at a wide dose spectrum. Among IMRT, HT lead to superior rectum sparing, whereas SW displayed superior bladder sparing. CK revealed superior dosimetry for rectum and bladder at higher dose ranges. Author Disclosure: S. Scobioala: None. C. Kittel: None. U. Haverkamp: None. M. Channaoui: None. O. Habibeh: None. K. Elsayad: None. H.T. Eich: None.
2687 Multicenter Assessment of Stereotactic Body Radiation Therapy (SBRT) Boost in Intermediate-Risk Prostate Cancer: Biochemical Failure and Toxicity S.E. Finkelstein,1 J. Forman,2 E. Fernandez,3 C.T. Chen,4 M.E. Lieberfarb,3 S. Salenius,1 D.E. Dosoretz,1 A. Dosoretz,1 T.D. Shafman,1 and C.A. Mantz1; 121st Century Oncology, Fort Myers, FL, 221st Century Oncology, Farmington Hills, MI, 321st Century Oncology, Fort Lauderdale, FL, 421st Century Oncology, Plantation, FL Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) offers promise as a developing standard of care for localized prostate cancer. As compared to a conventional schedule, hypofractionated treatment may produce higher tumor control rates while maintaining an equivalent biologic effective dose (BED) to normal tissues for late effects and reducing BED for acute effects. Most previous single institution studies have
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specifically focused on patients with low risk prostate cancer with limited data available in intermediate (IRPC) or high risk prostate cancer. We describe toxicity and biochemical progression free survival outcomes of linear accelerator based SBRT boost for IRPC. Materials/Methods: This is a multi-center (9) retrospective review of prospectively collected data for a total of 60 patients; thirty-eight patients (63%) were treated on an IRB approved prospective trial. IRPC patients that included clinical stage T2b (7%) or PSA > 10 ng/ml and < 20 ng/ml (25%) or Gleason score of 7 (82%), received 45 Gy of IMRT in 25 fractions followed by a SBRT boost of 5.5 Gy per fraction for 4 fractions. Cone beam CT image guidance was used prior to each fraction for correction of target setup error. Twenty-three percent of patients received concomitant androgen deprivation therapy (ADT); forty-six patients (77%) deferred concomitant ADT. NCI CTCAE v3.0 was used to assess urinary and rectal toxicity at baseline, during treatment, and then at 1, 3, 6, 9, 12, 18, 24, 30, and 36 months after treatment. Biochemical determinations were made at concurrent follow up time points. IPSS and IEFF scores were also obtained at baseline and at follow up. Results: Median follow up was 21.5 months (range 2.9-87.2). No patient (0%) had a biochemical failure, using the combined ASTRO Phoenix definition. Mean PSA (ng/ml) at baseline was 8.5; 2.9 at 1, 1.7 at 3, 1.3 at 6, 0.8 at 9, 1.0 at 12, 0.7 at 18, 0.4 at 24, 0.3 at 30 months after treatment respectively. With respect to toxicity, Grade 3-5 Genitourinary (GU) toxicity was 3%, with 2 patients experiencing grade 3 (3%), and no patient experiencing grade 4 or 5 toxicity. The most common GU toxicity was urinary frequency/urgency, experienced by 35% of patients at baseline, peaking during treatment to 65%, declining to 24% by 12 months and thereafter remaining stable. Grade 3-5 Gastrointestinal (GI) toxicity was 2%, with 1 patient experiencing grade 3 (2%), and no grade 4 or 5 toxicity. Diarrhea was the most common side effect seen, 24% during treatment, all Grade 1. This toxicity resolved rapidly, with 4% at 12 months and 0% thereafter. Conclusion: Linear accelerator based SBRT boost for IRPC produces a rapid biochemical response with favorable urinary and rectal toxicity following treatment. Interestingly, a clinically significant number of patients had GU symptoms at baseline which improved over time. Further follow up is needed to determine long-term toxicity and disease control outcomes. Author Disclosure: S.E. Finkelstein: None. J. Forman: None. E. Fernandez: None. C.T. Chen: None. M.E. Lieberfarb: None. S. Salenius: None. D.E. Dosoretz: None. A. Dosoretz: None. T.D. Shafman: None. C.A. Mantz: None.
patient (2%) on anti-coagulation developed a grade 2 rectal bleed which resolved with steroid suppositories. Conclusion: Our study shows that the usage of a PEG rectal spacer in patients who have had a prostatectomy was well tolerated. Despite the high dose of salvage radiation therapy, the GI toxicity rates were low. Only one patient on anti-coagulation developed a late grade 2 rectal bleed which resolved after a few months with steroid suppositories. Author Disclosure: B. Lehrich: None. J. Yeh: None. J. Ravera: None. R. Torrey: None. J. Yoshida: None. R. Baghdassarian: None. A. Weinberg: None. K. Tokita: None.
2688 Postprostatectomy Patients Undergoing Salvage High-Dose External Beam Radiation With a Polyethylene Glycol (PEG) Spacer B. Lehrich, J. Yeh, J. Ravera, R. Torrey, J. Yoshida, R. Baghdassarian, A. Weinberg, and K. Tokita; Cancer Center of Irvine, Irvine, CA Purpose/Objective(s): Rectal spacer usage has been shown to decrease rectal toxicity in men undergoing radiation for prostate cancer. There have been few studies on its usage in the post-prostatectomy setting for salvage or adjuvant radiation. This study reports on the gastrointestinal toxicity of patients who underwent a prostatectomy and received high dose (>72 Gy) radiation therapy with the usage of an absorbable polyethylene glycol rectal spacer. Materials/Methods: From January 2010 to December 2015, a total of 69 patients had ultrasound guided transperineal injection of an absorbable PEG spacer anterior to the residual Denonvillier’s fascia. All patients were treated to a minimum of 72Gy to the prostatic fossa with IMRT (Intensity Modulated Radiation Therapy) with daily cone beam CT to ensure treatment accuracy. Acute and chronic rectal toxicity using the National Cancer Center Institute Common Terminology Criteria for Adverse Events v4.0 grading scheme was performed at the end of treatment, 3 months, and 6 months afterwards. Results: At the end of treatment, 35% of the 69 patients had grade 1 toxicity. No patient developed grade 2 or higher toxicity. At 3 months, 56 patients had follow up data. Thirteen percent had grade 1 toxicity. No patient developed grade 2 or higher toxicity. At 6 months, 50 patients had follow up data. Fourteen percent of patients had grade 1 toxicity. One
2689 The Effect of Comprehensive Pelvic Nodal Radiation in Prostate Cancer on the CBC D. Arora, R. Schurr, F. Zhang, M.M. Gestaut, J. Pruszynski, G.P. Swanson, and N. Deb; Baylor Scott & White Healthcare Temple Clinic, Temple, TX Purpose/Objective(s): Historically with radiation to the pelvis, the effect on blood count indices was not found to be clinically significant unless combined with chemotherapy. There has been some concern that with the higher integral dose (dose to larger volumes of tissue outside the normal treatment volume), there may be some unanticipated toxicities. We have defined the blood count toxicities of large volume pelvic marrow irradiation. Materials/Methods: We retrospectively reviewed a cohort of prostate cancer patients from a single institution (n Z 47) that received IMRT radiation to the prostate +/- lymphatics from November 2014 to November 2015. Doses included 78 Gy for intact prostate and 70 Gy in the adjuvant/ salvage setting. CBCs were examined at 3 time points: the start, completion, and 3 months after radiation therapy. Pelvic bone dosimetry parameters of V20 (%volume receiving 20 Gy) and V40 (% volume receiving 40 Gy) were analyzed in relation to CBC. Androgen deprivation and lymph node radiation were also examined in relation to CBC. Results: Of the 47 patients with prostate cancer, 28 patients or 60% of all patients received 78 Gy to the prostate and 19 patients or 40% received 70 Gy to the prostate bed. A total of 39 or 83% had lymphatic radiation and 20 or 43% received androgen deprivation prior to radiation. Lymph node radiation had a significantly higher V20 and V40 verses prostate radiation alone (P<0.0001). Lymph node radiation was associated with a mean of 2 point drop in white blood cell count (WBCs), 1 point drop in hemoglobin, and 10 point drop in platelets. Androgen deprivation did not affect the overall WBC, hemoglobin, or platelet mean. For all patients, there was a drop in mean WBC, hemoglobin, and platelets as seen in Table 1. For all patients, mean/ median V20 was 56.2/64 and mean/median V40 vas 24.2/27. Abstract 2689; Table 1. Mean/Median CBC at Start, Completion, and 3 months after Radiation CBC value
Mean/Median at start
Mean/Median at Completion
Mean/Median 3 months later
WBC Hemoglobin Platelet
7/6.8 13.8/14 208.6/194
4.9/4.8 13/12.9 186.4/178
5.42/5.1 13.3/13.4 192.8/187
There was a weak correlation between drop in WBC and the V20 and V40 (P Z 0.07 and P Z 0.53 respectively). There was a weak correlation between drop in platelets and the V20 and V40 (P Z 0.14 and P Z 0.13 respectively). There was however, a statistically significant drop in hemoglobin with V20 of 55% or more and a trend towards significance with V40 of 23% or more (P Z 0.04 and P Z 0.05 respectively). Conclusion: While in general, there was a drop in blood parameters with prostate radiation, this was not well correlated with the volume of the pelvis receiving 20 or 40 Gy. For hemoglobin, there was a significant drop if the V20 exceeded 55%. This may be the reason many patients experience fatigue while undergoing prostate cancer radiation therapy. These results suggest that the effect on blood counts is not related solely to the volume of bone marrow radiated.
2685 The Outcomes of Adjuvant Radiation Therapy in Postcystectomy Muscle-Invasive Bladder Cancer L.C. Tuanquin,1 D. McDermott,2 H.B. Mackley,2 S. Holder,2 H. Wagner, Jr,3 J.C. Rosenberg,2 J.J. Drabick,2 M. Kaag,2 M. Joshi,2 J. Raman,2 and S.B. Merrill2; 1Penn State Hershey Cancer Institute, Hershey, PA, 2Penn State Hershey Medical Center, Hershey, PA, 3Penn State Hershey Medical Center, Hershey, PA, United States Purpose/Objective(s): A current standard of care treatment for locally advanced but clinically node negative bladder cancer is radical cystectomy with neoadjuvant chemotherapy. Locoregional failure following cystectomy however remains a significant source of morbidity, and is associated with adverse pathologic features including positive surgical margins (SM+). The selection criteria for postoperative radiation therapy (PORT) and clinical effectiveness with PORT have not been well-established. The objective of this study is to evaluate clinical and pathologic features, and associated outcomes, in patients who received PORT for pT3-T4, pN0-1 M0 muscle invasive bladder cancer. Materials/Methods: The patients chosen for this retrospective review were compiled via the cancer registry at Penn State Hershey Medical Center from 1995-2015. Sixty-three patients were identified as having non-metastatic muscle invasive bladder cancer on initial presentation, who underwent cystectomy, and staged as pT3-pT4, pN0-N1. Analysis was done on a cohort of patients that received PORT with a cohort that did not. Results: Ten patients received PORT using IMRT, with one of the patients unable to complete the entire course due to toxicity, and 53 patients did not. Radiation dose ranged from 34.2-58 Gy. The PORT group had 70% urothelial histology and 60% had SM+ compared to 92% and 6%, respectively, in the non-PORT group [both statistically significant (P Z 0.038 and P Z <0.001 respectively)]. The entire cohort local recurrence (LR) rate was 28%. The PORT group had a 40% LR rate with the majority of these cases being gastrointestinal in location. The overall distant recurrence rate was 25% with no significance between the groups. The entire cohort 5-yr disease free survival (DFS) rate was 30%, and the 5-yr overall survival (OS) rate was 41%. The 5-year DFS rates were 20% in the PORT group versus 32% in the non-PORT group [not statistically significant (hazard ratio [HR] 1.498, 95% confidence interval [CI] 0.539-4.1663, log-rank P Z 0.361)]. The 5-yr OS rates were 30% in the PORT group versus 43% in the non-PORT group [not statistically significant ([HR] 0.863, [CI] 0.357-2.089, log-rank P Z 0.75)]. Multivariate analysis showed that SM+ was significant for 5-yr DFS, while nodal status and stage were significant for 5-yr OS. Conclusion: Post-cystectomy local recurrence rates were high despite the use of PORT in patients with high risk features. When considering a 5-yr OS of about 40%, reducing pelvic failure remains a critical goal. Studies evaluating the clinical target volume, radiation dose, and patterns of failure should help refine the selection criteria of patients most likely to benefit from PORT. Author Disclosure: L.C. Tuanquin: None. D. McDermott: None. H.B. Mackley: None. S. Holder: None. H. Wagner: None. J.C. Rosenberg: None. J.J. Drabick: None. M. Kaag: None. M. Joshi: None. J. Raman: None. S.B. Merrill: None.
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2686 A Dosimetric Comparison Between Conventionally Fractionated Tomotherapy, Volumetric Modulated Arc Therapy, Sliding Window and Proton Therapy, and Hypofractionated Robotic Radiosurgery Treatment by Low-Risk Prostate Carcinoma S. Scobioala,1 C. Kittel,1 U. Haverkamp,2 M. Channaoui,1 O. Habibeh,1 K. Elsayad,2 and H.T.T. Eich1; 1Radiation Oncology Department, University Hospital Muenster, Muenster, Germany, 2Department of Radiation Oncology, University Hospital Muenster, Muenster, Germany Purpose/Objective(s): Using statistical dosimetric comparison to ascertain the optimal radiation technique and fractionation regime for the treatment of low-risk prostate cancer. Materials/Methods: The treatment plans were generated from 20 randomly selected patients with low-risk prostate cancer. A dosimetric comparison was performed between a helical 3DCRT and IMRT system (HT), Sliding Window (SW), volumetric modulated arc therapy (VMAT) and protons, providing a conventional fractionation, and hypofractionated frameless robotic radiosurgery system-based stereotactic body radiation therapy (SBRT). Target doses were calculated to 79.2Gy for the conventional regime and 36.25Gy for SBRT. The dosimetric parameters for the planning target volume (PTV) and organs at risk (OAR), including a homogeneity index (HI) and four conformity indexes (CI), were comparatively analyzed. Results: The patient-averaged dose volume histogram revealed similar D98% and D2% values between techniques except for CK. HT, SW, VMAT and protons demonstrated similar HI values, which were superior to the CK homogeneity values. All techniques displayed high conformity values, with a slightly lower CI values for HT (P<.01). The dose distributions showed greater differences at low-to-medium doses than at higher doses. Protons demonstrated statistically superior rectum sparing at low-to-higher dose ranges (V10-V70, P<.01) and bladder sparing at low-to-medium doses (V10-V30, P<.01). Among the intensity-modulated approaches (IMRT), HT provided an improved rectum sparing (P<.01 versus SW and VMAT) and SW revealed superior bladder sparing (P<.01 versus HT and VMAT). CK provided superior bladder shielding at higher doses compared to other techniques (V50-V70, P<.01), and improved rectum sparing at V50 versus SW and VMAT (P<.01). Protons and CK generated significantly higher exposures of the femoral heads and HT had superior sparing of those. Conclusion: We provided a statistical dosimetric comparison between various advanced radiation techniques, comparing conventional to hypofractionated regimes in the treatment of low-risk prostate cancer. Higher homogeneity was observed for techniques applying conventional fractionation compared to CBbased SBRT. HT demonstrated slightly lower conformity than other techniques. With the exception of femoral heads, protons demonstrated significantly superior sparing of OAR at a wide dose spectrum. Among IMRT, HT lead to superior rectum sparing, whereas SW displayed superior bladder sparing. CK revealed superior dosimetry for rectum and bladder at higher dose ranges. Author Disclosure: S. Scobioala: None. C. Kittel: None. U. Haverkamp: None. M. Channaoui: None. O. Habibeh: None. K. Elsayad: None. H.T. Eich: None.
2687 Multicenter Assessment of Stereotactic Body Radiation Therapy (SBRT) Boost in Intermediate-Risk Prostate Cancer: Biochemical Failure and Toxicity S.E. Finkelstein,1 J. Forman,2 E. Fernandez,3 C.T. Chen,4 M.E. Lieberfarb,3 S. Salenius,1 D.E. Dosoretz,1 A. Dosoretz,1 T.D. Shafman,1 and C.A. Mantz1; 121st Century Oncology, Fort Myers, FL, 221st Century Oncology, Farmington Hills, MI, 321st Century Oncology, Fort Lauderdale, FL, 421st Century Oncology, Plantation, FL Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) offers promise as a developing standard of care for localized prostate cancer. As compared to a conventional schedule, hypofractionated treatment may produce higher tumor control rates while maintaining an equivalent biologic effective dose (BED) to normal tissues for late effects and reducing BED for acute effects. Most previous single institution studies have
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International Journal of Radiation Oncology Biology Physics
specifically focused on patients with low risk prostate cancer with limited data available in intermediate (IRPC) or high risk prostate cancer. We describe toxicity and biochemical progression free survival outcomes of linear accelerator based SBRT boost for IRPC. Materials/Methods: This is a multi-center (9) retrospective review of prospectively collected data for a total of 60 patients; thirty-eight patients (63%) were treated on an IRB approved prospective trial. IRPC patients that included clinical stage T2b (7%) or PSA > 10 ng/ml and < 20 ng/ml (25%) or Gleason score of 7 (82%), received 45 Gy of IMRT in 25 fractions followed by a SBRT boost of 5.5 Gy per fraction for 4 fractions. Cone beam CT image guidance was used prior to each fraction for correction of target setup error. Twenty-three percent of patients received concomitant androgen deprivation therapy (ADT); forty-six patients (77%) deferred concomitant ADT. NCI CTCAE v3.0 was used to assess urinary and rectal toxicity at baseline, during treatment, and then at 1, 3, 6, 9, 12, 18, 24, 30, and 36 months after treatment. Biochemical determinations were made at concurrent follow up time points. IPSS and IEFF scores were also obtained at baseline and at follow up. Results: Median follow up was 21.5 months (range 2.9-87.2). No patient (0%) had a biochemical failure, using the combined ASTRO Phoenix definition. Mean PSA (ng/ml) at baseline was 8.5; 2.9 at 1, 1.7 at 3, 1.3 at 6, 0.8 at 9, 1.0 at 12, 0.7 at 18, 0.4 at 24, 0.3 at 30 months after treatment respectively. With respect to toxicity, Grade 3-5 Genitourinary (GU) toxicity was 3%, with 2 patients experiencing grade 3 (3%), and no patient experiencing grade 4 or 5 toxicity. The most common GU toxicity was urinary frequency/urgency, experienced by 35% of patients at baseline, peaking during treatment to 65%, declining to 24% by 12 months and thereafter remaining stable. Grade 3-5 Gastrointestinal (GI) toxicity was 2%, with 1 patient experiencing grade 3 (2%), and no grade 4 or 5 toxicity. Diarrhea was the most common side effect seen, 24% during treatment, all Grade 1. This toxicity resolved rapidly, with 4% at 12 months and 0% thereafter. Conclusion: Linear accelerator based SBRT boost for IRPC produces a rapid biochemical response with favorable urinary and rectal toxicity following treatment. Interestingly, a clinically significant number of patients had GU symptoms at baseline which improved over time. Further follow up is needed to determine long-term toxicity and disease control outcomes. Author Disclosure: S.E. Finkelstein: None. J. Forman: None. E. Fernandez: None. C.T. Chen: None. M.E. Lieberfarb: None. S. Salenius: None. D.E. Dosoretz: None. A. Dosoretz: None. T.D. Shafman: None. C.A. Mantz: None.
patient (2%) on anti-coagulation developed a grade 2 rectal bleed which resolved with steroid suppositories. Conclusion: Our study shows that the usage of a PEG rectal spacer in patients who have had a prostatectomy was well tolerated. Despite the high dose of salvage radiation therapy, the GI toxicity rates were low. Only one patient on anti-coagulation developed a late grade 2 rectal bleed which resolved after a few months with steroid suppositories. Author Disclosure: B. Lehrich: None. J. Yeh: None. J. Ravera: None. R. Torrey: None. J. Yoshida: None. R. Baghdassarian: None. A. Weinberg: None. K. Tokita: None.
2688 Postprostatectomy Patients Undergoing Salvage High-Dose External Beam Radiation With a Polyethylene Glycol (PEG) Spacer B. Lehrich, J. Yeh, J. Ravera, R. Torrey, J. Yoshida, R. Baghdassarian, A. Weinberg, and K. Tokita; Cancer Center of Irvine, Irvine, CA Purpose/Objective(s): Rectal spacer usage has been shown to decrease rectal toxicity in men undergoing radiation for prostate cancer. There have been few studies on its usage in the post-prostatectomy setting for salvage or adjuvant radiation. This study reports on the gastrointestinal toxicity of patients who underwent a prostatectomy and received high dose (>72 Gy) radiation therapy with the usage of an absorbable polyethylene glycol rectal spacer. Materials/Methods: From January 2010 to December 2015, a total of 69 patients had ultrasound guided transperineal injection of an absorbable PEG spacer anterior to the residual Denonvillier’s fascia. All patients were treated to a minimum of 72Gy to the prostatic fossa with IMRT (Intensity Modulated Radiation Therapy) with daily cone beam CT to ensure treatment accuracy. Acute and chronic rectal toxicity using the National Cancer Center Institute Common Terminology Criteria for Adverse Events v4.0 grading scheme was performed at the end of treatment, 3 months, and 6 months afterwards. Results: At the end of treatment, 35% of the 69 patients had grade 1 toxicity. No patient developed grade 2 or higher toxicity. At 3 months, 56 patients had follow up data. Thirteen percent had grade 1 toxicity. No patient developed grade 2 or higher toxicity. At 6 months, 50 patients had follow up data. Fourteen percent of patients had grade 1 toxicity. One
2689 The Effect of Comprehensive Pelvic Nodal Radiation in Prostate Cancer on the CBC D. Arora, R. Schurr, F. Zhang, M.M. Gestaut, J. Pruszynski, G.P. Swanson, and N. Deb; Baylor Scott & White Healthcare Temple Clinic, Temple, TX Purpose/Objective(s): Historically with radiation to the pelvis, the effect on blood count indices was not found to be clinically significant unless combined with chemotherapy. There has been some concern that with the higher integral dose (dose to larger volumes of tissue outside the normal treatment volume), there may be some unanticipated toxicities. We have defined the blood count toxicities of large volume pelvic marrow irradiation. Materials/Methods: We retrospectively reviewed a cohort of prostate cancer patients from a single institution (n Z 47) that received IMRT radiation to the prostate +/- lymphatics from November 2014 to November 2015. Doses included 78 Gy for intact prostate and 70 Gy in the adjuvant/ salvage setting. CBCs were examined at 3 time points: the start, completion, and 3 months after radiation therapy. Pelvic bone dosimetry parameters of V20 (%volume receiving 20 Gy) and V40 (% volume receiving 40 Gy) were analyzed in relation to CBC. Androgen deprivation and lymph node radiation were also examined in relation to CBC. Results: Of the 47 patients with prostate cancer, 28 patients or 60% of all patients received 78 Gy to the prostate and 19 patients or 40% received 70 Gy to the prostate bed. A total of 39 or 83% had lymphatic radiation and 20 or 43% received androgen deprivation prior to radiation. Lymph node radiation had a significantly higher V20 and V40 verses prostate radiation alone (P<0.0001). Lymph node radiation was associated with a mean of 2 point drop in white blood cell count (WBCs), 1 point drop in hemoglobin, and 10 point drop in platelets. Androgen deprivation did not affect the overall WBC, hemoglobin, or platelet mean. For all patients, there was a drop in mean WBC, hemoglobin, and platelets as seen in Table 1. For all patients, mean/ median V20 was 56.2/64 and mean/median V40 vas 24.2/27. Abstract 2689; Table 1. Mean/Median CBC at Start, Completion, and 3 months after Radiation CBC value
Mean/Median at start
Mean/Median at Completion
Mean/Median 3 months later
WBC Hemoglobin Platelet
7/6.8 13.8/14 208.6/194
4.9/4.8 13/12.9 186.4/178
5.42/5.1 13.3/13.4 192.8/187
There was a weak correlation between drop in WBC and the V20 and V40 (P Z 0.07 and P Z 0.53 respectively). There was a weak correlation between drop in platelets and the V20 and V40 (P Z 0.14 and P Z 0.13 respectively). There was however, a statistically significant drop in hemoglobin with V20 of 55% or more and a trend towards significance with V40 of 23% or more (P Z 0.04 and P Z 0.05 respectively). Conclusion: While in general, there was a drop in blood parameters with prostate radiation, this was not well correlated with the volume of the pelvis receiving 20 or 40 Gy. For hemoglobin, there was a significant drop if the V20 exceeded 55%. This may be the reason many patients experience fatigue while undergoing prostate cancer radiation therapy. These results suggest that the effect on blood counts is not related solely to the volume of bone marrow radiated.