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Intraprostatic Boost Using High-dose-rate Brachytherapy (HDR-BT) According to Gross Tumor Volume (GTV) Location for Prostate Cancer: A Dosimetric Feasibility Study
Volume 84 Number 3S Supplement 2012 hormones did not influence acute or chronic toxicity rates between radiation treatment groups. Chronic grade 3 urinary retention was higher, however, in patients treated with ADT (2.6% vs. 0.7%, p Z 0.03). Mean dose in 3D-CRT and IMRT groups was 75.1 Gy and 76.3 Gy, respectively (p < 0.001), while mean dose for Group 1 was 75.2 Gy vs. 76.4 Gy for Group 2 (p < 0.001). In the IMRT group, the mean dose for Group 1 was lower than Group 2 (75.5 Gy vs. 76.8 Gy, p < 0.001). This was not true for 3D-CRT cases. Dysuria and frequency were the most common acute grade 2 GU toxicities (3.0% and 8.4%), which decreased after six months (1.4% and 4.7%). Urinary incontinence, however, increased over time (0.6% acute, 1.7% chronic) as did grade 2 rectal bleeding/proctitis (0%/0.2% acute vs. 3.4%/2.2% chronic). We found less acute grade 1 rectal bleeding with IMRT vs. 3D-CRT (9.5% vs. 1.3%, p Z 0.04). Chronic toxicities were largely similar between techniques except for grade 1 rectal bleeding again being lower for IMRT (11.2% vs. 6.8%, p < 0.02). Within the IMRT cohort, Group 2 patients (with larger CTVs) had higher rates of grade 2 rectal bleeding (5.2% vs. 1.4%, p Z 0.01), while all other toxicities were not statistically different. Conclusion: For prostate cancer patients receiving IGART, a higher mean radiation therapy dose may be achieved using IMRT with equal or lower rates of GI and GU toxicity. Additional study to decrease side effects for higher-risk patients with larger target volumes is warranted. Author Disclosure: N. Tonlaar: None. J.B. Wilkinson: None. D.S. Brabbins: None. J.T. Dilworth: None. H. Ye: None. M. Wallace: None. I. Grills: None. D. Yan: None. G. Gustafson: None. D.J. Krauss: None.
2479 Stereotactic Body Radiotherapy (SBRT) for Low Risk Prostate Cancer: Plan comparison With Real Time Tracking By Beacons and Helical Tomotherapy A. Sen, D. Lollar, W. Falwell, H. Sakhalkar, P. Sourivong, W.C. Goad, M.S. Payne, O. Taylor, and J.P. Flynn; Cancer Treatment Centers of America, Tulsa, OK Purpose/Objective(s): Hypofractionated treatment of low risk prostate cancer by external beam are planned and delivered using rotational arc (RA) treatment planning on a conventional linac. Treatment plans are generated retrospectively on helical Tomotherapy (HT) for comparison. Materials/Methods: Eight low risk prostate patients were implanted each with three commercial beacons. RA plans were generated on an Eclipse planning system and delivered using CBCT image guidance for localization and real time tracking of beacons. Dose fractionation was 7.25 Gy/fx for 5 fractions to a total dose of 36.25 Gy. Planning goals were set for 95% of the planning target volume (PTV) to receive at least the prescription dose. Treatment plans were also generated on a HT planning system using the same fractionation and dose-volume constraints. Margins for the PTV were set at 5 mm in all directions except 3 mm posteriorly. Treatment plans were evaluated based on the target coverage measured by minimum, mean and maximum dose to the target volumes in the dose-volume-histogram (DVH) analysis and the conformity index (CI).The heterogeneity of the dose distribution in the PTV was measured by a dose heterogeneity index as DHI. The volumes covering 5, 10, 20, 50 and 70% of the prescription dose (V5, V10, V20, V50 and V70) for two OARs were determined. Results: The mean age of the patients was 61 y (range 53-79) and the mean prostate volume was 49.1 cm3 (range 30.3-77.4 cm3). The mean PSA value was 7.0 ng/mL (range 3.8-8.91). All patients were staged at T1cN0M0 except for one at T1bN0M0. For the RA plans the average values of monitor units (MU), actual beam delivery time, CI and DHI are 3193, 328.6 s, 1.194 and 2.88, respectively. The equivalent biological dose at 2 Gy/fx (EQD2) for the SBRT treatment was 90.63 Gy with an a/b ratio of 1.5 for prostate. For HT plans, the average values of the monitor units, treatment beam-on time, CI and DHI are 14330, 984.9 s, 1.307 and 3.22, respectively. Conclusions: Analysis of the DVH data shows that, on average, the minimum dose coverage of the PTV for RA plans is 4% higher than the HT plans. The averages of the maximum and mean dose coverage of the PTV for the two planning systems are almost same. The average monitor unit and beam-on time for HT plans are 4.5 and 3 times, respectively, higher than the RA plans. Thus the RA treatment is more efficient. The CI
Poster Viewing Abstracts S399 of the RA plans is slightly better than the HT plans e the average being about 10% lower for the RA plans. Also, the dose heterogeneity of the PTV in the RA plans is around 12% lower than the HT plans. Comparison of the averages of the minimum, maximum and mean doses for the rectum and bladder shows no statistical difference between the two planning systems.
2480 Decreasing Utilization of Brachytherapy for the Treatment of Prostate Cancer: A National Pattern of Care Analysis Using NCCN Risk Categorization U. Mahmood,1 M. Koshy,2 T. Pugh,1 K. Hoffman,1 D. Kuban,1 and A. Lee1; 1M.D. Anderson Cancer Center, Houston, TX, 2University of Chicago, Chicago, IL Purpose/Objective(s): External beam radiation therapy and brachytherapy are sometimes competing treatment modalities for localized prostate cancer. Previous patterns of care analyses had shown increasing utilization of brachytherapy relative to external beam radiation therapy during the 1990’s. Our aim was to analyze more recent trends in the utilization of these two radiation treatment modalities using a large, population-based US database. Materials/Methods: Using the Surveillance, Epidemiology, and End Results (SEER) database, information was obtained for all patients diagnosed with localized adenocarcinoma of the prostate between 2004 and 2008. Patients were classified as low (T1-2a, GS 6, and PSA < 10), intermediate (T2b-c, GS 7, or PSA 10-20), or high (T3a-4, GS 8, or PSA > 20) risk according to the NCCN risk categories. Trends in the utilization of external beam radiation therapy (EBRT), brachytherapy (BT), or combination therapy (BT + EBRT) were analyzed by year of diagnosis using regression analysis. For the purposes of this analysis, brachytherapy included both LDR and HDR techniques. Results: A total of 57,968 patients were identified. Median age for the entire cohort was 68 years old. A total of 22,108 (38%) were classified as low risk, 24,250 (42%) were classified as intermediate risk, and 11,610 (20%) were classified as high risk. When analyzing all patients, EBRT use increased from 57% in 2004 to 62% in 2008 whereas BT use correspondingly decreased from 31% in 2004 to 26% in 2008 (p < 0.0001). BT + EBRT use, on the other hand, remained at 12% between 2004 and 2008. When analyzed by NCCN risk categories, the increasing utilization of EBRT was most pronounced among low risk patients (9% increase) versus intermediate (3% increase) and high (0% change) risk patients. Correspondingly, the decreasing utilization of BT was most pronounced among low risk patients (7% decrease) versus intermediate (3% decrease) and high (2% decrease) risk patients. The utilization of BT + EBRT remained relatively stable among low (1% decrease), intermediate (0% change), and high (2% increase) risk patients. Conclusions: This patterns of care analysis reveals decreasing utilization of brachytherapy relative to external beam radiation therapy, which is most pronounced among lower risk patients. Although our analysis did not address the cause of this trend, we hypothesize that it may be the result of changing patient/physician preference, lack of emphasis on brachytherapy during radiation oncology training, and/or physician reimbursement/selfreferral. Author Disclosure: U. Mahmood: None. M. Koshy: None. T. Pugh: None. K. Hoffman: None. D. Kuban: None. A. Lee: None.
2481 Intraprostatic Boost Using High-dose-rate Brachytherapy (HDR-BT) According to Gross Tumor Volume (GTV) Location for Prostate Cancer: A Dosimetric Feasibility Study J. Helou,1 R. Verstraet,2 P. Blanchard,1 A. Rodriguez,2 J. Bourhis,1 D. Lefkopoulos,2 L. Calmels,2 F. Azoury,1 and A. Bossi1; 1Institut Gustave Roussy, Radiation Oncology department, Villejuif, France, 2Institut Gustave Roussy, Medical Physics department, Villejuif, France
S400
International Journal of Radiation Oncology Biology Physics
Purpose/Objective(s): HDR-BT allows for dose escalation to the whole prostatic gland volume and for a selective intra-prostatic GTV boost. Short and long term urethral and rectal toxicity may limit intra-prostatic dose escalation. Our study aims to identify the dosimetric feasibility and limitations of an intra-prostatic boost to different GTVs locations according to 4 dose levels. Materials/Methods: The study was conducted on 18 patients treated on an institutional protocol of combined HDR-BT single fraction of 9.5 Gy (Z Prescribed dose, PD) followed by EBRT delivered with Intensity modulated technique (IMRT) to a total dose of 46 Gy to the seminal vesicles and 60 Gy to the prostate alone (Z CTV). The GTV locations studied for the intra-prostatic boost were; postero-lateral, total posterior, antero-lateral, total anterior and 3 volumes in the apical zone characterized by different heights in the apex-base direction: 15, 20 and 25 mm. All patients had a standard optimization with the 90% of the CTV receiving 100 to 105% of the PD. The intra-prostatic boostdose levels studied were 100%, 120%, 135% and 150% of the PD. For every boost-dose level, we reported the D90%, V100%, 120%, 150% and 200% of the CTVand of the GTV, as well as the rectal and urethral D0.1cc and D0.5cc. Results: The D90 was 100% regardless of the boost location and dose. An intraprostatic dose escalation on the postero-lateral GTV had no significant impact on the urethral D0.1cc and D0.5cc, while a significant increase in the rectal D0.1cc (74, 77, 80 and 84% for every dose level respectively) and D0.5cc (68, 70, 72 and 75%) was noted (p < 0.05). Similarly, a boost on the total posterior GTV had a significant impact on the rectal D0.1cc (74, 77, 78 and 81%) and D0.5cc (67, 70, 71 and 73%) (p < 0.05), while the urethral D0.1cc increased significantly only for a boost of 150% (p Z 0.013). An antero-lateral and total anterior boost significantly increased the urethral D0.1cc for a dose 135% (p Z 0.007 and 0.01 respectively) while significantly decreasing the rectal doses. No significant impact of an apical dose escalation was seen on the urethra whereas the rectal doses increased significantly for a boost 135% (p < 0.05). No major increase on rectal and urethral doses was observed with the 120% boost level except for the posterior GTV (D0.1cc Z 77%). However, this increase is still within acceptable limits. Conclusion: Our data show that delivering an intra-prostatic boost of 120% of the PD is safe regardless of the GTV location. Further increases of the intra-prostatic boost dose may be possible only by carefully evaluating the spatial distribution of the GTV as well as the rectal and urethral doses. Author Disclosure: J. Helou: None. R. Verstraet: None. P. Blanchard: None. A. Rodriguez: None. J. Bourhis: None. D. Lefkopoulos: None. L. Calmels: None. F. Azoury: None. A. Bossi: None.
inhibitors (5AP), and phosphodiesterase inhibitors. Pts were followed from 2 to 17.5 years (median 6). Pre-treatment PSA was 0.3 - 300 ng/mL (median 6.6). Gleason scores were 6 in 62.4%, 7 in 25.8%, and 8-10 in 11.8%. Pts were divided into NCCN risk categories of low in 45.3%, intermediate in 37.2%, and high in 17.4%. Assuming an alpha beta ratio of 2, patients were treated with a BED of 99.5-320 Gy2 (median 202.6 Gy2). Phoenix definition of PSA failure was used. Results: The overall freedom from PSA failure (FPF) at 12 years for those on a medication versus not were 85.7% vs. 84.4% for ACE/ARB (p Z 0.04); 61.8% vs. 85.2% for folic acid (p Z 0.02); and 74% vs. 84.9% for 5AP (p Z 0.01). No individual medication appeared to confer an overall or cause specific survival advantage at 12 years. ACE/ARB use continued to show a positive significant effect (p Z 0.004) and Folate use a negative effect (p < 0.0001) on FPF in Cox regression with the covariates of Hormone use, Gleason score, initial PSA, NCCN risk category, total BED, and 5AP use. In contrast, 5AP lost its significant effect on FPF in multivariable analysis. Conclusions: AB appears to confer a FPF advantage for pts receiving definitive radiation, while Folate supplementation portends a worse FPF. These findings are hypothesis generating, suggest a potential role for adjusting medication subtype during treatment, and call for further research to elucidate their possible mechanism of action during definitive radiation therapy for PC. Author Disclosure: S.R. Blacksburg: None. E.C. Ko: None. N.N. Stone: E. Research Grant; DOD, NIH. G. Consultant; Amgen, Bayer, DCMI, Ferring, Centacor Biotech. P. Ownership Other; Prologics LLC. R.G. Stock: None.
2482 The Potential Impact of Medications on Biochemical Control Following Definitive Management of Prostate Cancer S.R. Blacksburg, E.C. Ko, N.N. Stone, and R.G. Stock; Mount Sinai Medical Center, New York, NY Purpose: A growing body of literature has demonstrated the impact of medication on the incidence and all cause mortality related to prostate cancer (PC). This has been demonstrated through pre-clinical studies, the Cancer of the Prostate Strategic Urologic Research Endeavor database, as well as numerous meta-analyses. Folate supplementation has been associated with increased incidence of PC and the modulation of angiotensin II blockade (AB) has been implicated in reduced PC incidence and all cause mortality risk. However, the role of medication on treatment-related outcome is lacking. The potential effect of these medications on biochemical control following definitive radiation for PC was analyzed. Material and Methods: A total of 1,912 PC patients (pts) were treated with definitive radiation, including external beam radiation and low dose rate brachytherapy regimens, from 1990 through 2010. Classes of medication documented included calcium channel blockers, statins, beta blockers, ACE-inhibitors/angiotensin receptor blockers (ACE/ARB), folic acid, proton pump inhibitors, alpha-1 adrenergic blockers, HIV medication, metformin and oral hypoglycemics, histamine blockers, non-steroidal antiinflammatory drugs, steroids, selective serotonin reuptake inhibitors, insulin, aspirin, warfarin, clopidogrel, diuretics, 5-alpha reductase
2483 What Daily Image Guidance Is Needed for Prostate Cancer Patients Post Radical Prostatectomy? Data From a Pilot Phase II Study T.M. Niazi, B. Bahoric, N. Tomic, and T. Vuong; Segal Cancer Centre, Jewish General Hospital. McGill University, Montreal, QC, Canada Purpose/Objective(s): Image guided Radiation Therapy (RT) for prostate cancer patients is becoming the norm in developed countries. For prostate in place ultrasound and Cone Beam Computed Tomography (CBCT) are the two commonly used target localizing modalities, while KvKv (orthogonal) images and CBCT can be used for patients requiring salvage or adjuvant radiation therapy post radical prostatectomy (RP). In this study we assessed if Kv-Kv localization images are sufficient for patients requiring adjuvant or salvage RT. Materials/Methods: As per our standard of care all prostate cancer patients, requiring adjuvant or salvager RT, undergo CBCT for target localization. Twenty-four such patients, with radio-opaque surgical clips, agreed to participate into this phase II study. After informed written consent, these patients underwent two orthogonal Kv-Kv images prior to the routine CBCT at each RT fraction. Treatment target volumes were initially localized using the Kv-Kv images, however, the final treatment was based on the CBCT 3-dimensional shifts (vertical, lateral and longitudinal). For each patient the Kv-Kv shifts were than compared with CBCT at each fraction and a mean value was obtained. The mean values of the two approaches were then analyzed, individually and collectively. Results: Twenty-four prostate cancer patients, requiring post RP salvage or adjuvant RT, took part into this prospective study. The mean shift, after Kv-Kv localization, was 0.18 cm laterally, 0.23 cm vertically, and 0.21 cm longitudinally with respective standard deviation (SD) of: 0.12; 0.1 and 0.11. However, the mean for the maximum difference in the treatment shifts were 0.6 cm, 0.61 cm and 0.68 cm respectively with SD of 0.45, 0.30 and 0.48 respectively. Individual dimensional analysis revealed maximum shifts of up to 1.5 cm. Conclusions: From the cumulative mean values, magnitude of the difference averaged over all treatment fractions, the difference between CBCT and Kv-Kv, using clips, is less than 5 mm. However, the difference for the maximum shift could be up to 1.5 cm in one direction. Therefore, we conclude that CBCT is the superior imaging modality that uses soft tissue to align with target contour in 3D and it is the most accurate as compared to Kv-Kv.
2479 Stereotactic Body Radiotherapy (SBRT) for Low Risk Prostate Cancer: Plan comparison With Real Time Tracking By Beacons and Helical Tomotherapy A. Sen, D. Lollar, W. Falwell, H. Sakhalkar, P. Sourivong, W.C. Goad, M.S. Payne, O. Taylor, and J.P. Flynn; Cancer Treatment Centers of America, Tulsa, OK Purpose/Objective(s): Hypofractionated treatment of low risk prostate cancer by external beam are planned and delivered using rotational arc (RA) treatment planning on a conventional linac. Treatment plans are generated retrospectively on helical Tomotherapy (HT) for comparison. Materials/Methods: Eight low risk prostate patients were implanted each with three commercial beacons. RA plans were generated on an Eclipse planning system and delivered using CBCT image guidance for localization and real time tracking of beacons. Dose fractionation was 7.25 Gy/fx for 5 fractions to a total dose of 36.25 Gy. Planning goals were set for 95% of the planning target volume (PTV) to receive at least the prescription dose. Treatment plans were also generated on a HT planning system using the same fractionation and dose-volume constraints. Margins for the PTV were set at 5 mm in all directions except 3 mm posteriorly. Treatment plans were evaluated based on the target coverage measured by minimum, mean and maximum dose to the target volumes in the dose-volume-histogram (DVH) analysis and the conformity index (CI).The heterogeneity of the dose distribution in the PTV was measured by a dose heterogeneity index as DHI. The volumes covering 5, 10, 20, 50 and 70% of the prescription dose (V5, V10, V20, V50 and V70) for two OARs were determined. Results: The mean age of the patients was 61 y (range 53-79) and the mean prostate volume was 49.1 cm3 (range 30.3-77.4 cm3). The mean PSA value was 7.0 ng/mL (range 3.8-8.91). All patients were staged at T1cN0M0 except for one at T1bN0M0. For the RA plans the average values of monitor units (MU), actual beam delivery time, CI and DHI are 3193, 328.6 s, 1.194 and 2.88, respectively. The equivalent biological dose at 2 Gy/fx (EQD2) for the SBRT treatment was 90.63 Gy with an a/b ratio of 1.5 for prostate. For HT plans, the average values of the monitor units, treatment beam-on time, CI and DHI are 14330, 984.9 s, 1.307 and 3.22, respectively. Conclusions: Analysis of the DVH data shows that, on average, the minimum dose coverage of the PTV for RA plans is 4% higher than the HT plans. The averages of the maximum and mean dose coverage of the PTV for the two planning systems are almost same. The average monitor unit and beam-on time for HT plans are 4.5 and 3 times, respectively, higher than the RA plans. Thus the RA treatment is more efficient. The CI
Poster Viewing Abstracts S399 of the RA plans is slightly better than the HT plans e the average being about 10% lower for the RA plans. Also, the dose heterogeneity of the PTV in the RA plans is around 12% lower than the HT plans. Comparison of the averages of the minimum, maximum and mean doses for the rectum and bladder shows no statistical difference between the two planning systems.
2480 Decreasing Utilization of Brachytherapy for the Treatment of Prostate Cancer: A National Pattern of Care Analysis Using NCCN Risk Categorization U. Mahmood,1 M. Koshy,2 T. Pugh,1 K. Hoffman,1 D. Kuban,1 and A. Lee1; 1M.D. Anderson Cancer Center, Houston, TX, 2University of Chicago, Chicago, IL Purpose/Objective(s): External beam radiation therapy and brachytherapy are sometimes competing treatment modalities for localized prostate cancer. Previous patterns of care analyses had shown increasing utilization of brachytherapy relative to external beam radiation therapy during the 1990’s. Our aim was to analyze more recent trends in the utilization of these two radiation treatment modalities using a large, population-based US database. Materials/Methods: Using the Surveillance, Epidemiology, and End Results (SEER) database, information was obtained for all patients diagnosed with localized adenocarcinoma of the prostate between 2004 and 2008. Patients were classified as low (T1-2a, GS 6, and PSA < 10), intermediate (T2b-c, GS 7, or PSA 10-20), or high (T3a-4, GS 8, or PSA > 20) risk according to the NCCN risk categories. Trends in the utilization of external beam radiation therapy (EBRT), brachytherapy (BT), or combination therapy (BT + EBRT) were analyzed by year of diagnosis using regression analysis. For the purposes of this analysis, brachytherapy included both LDR and HDR techniques. Results: A total of 57,968 patients were identified. Median age for the entire cohort was 68 years old. A total of 22,108 (38%) were classified as low risk, 24,250 (42%) were classified as intermediate risk, and 11,610 (20%) were classified as high risk. When analyzing all patients, EBRT use increased from 57% in 2004 to 62% in 2008 whereas BT use correspondingly decreased from 31% in 2004 to 26% in 2008 (p < 0.0001). BT + EBRT use, on the other hand, remained at 12% between 2004 and 2008. When analyzed by NCCN risk categories, the increasing utilization of EBRT was most pronounced among low risk patients (9% increase) versus intermediate (3% increase) and high (0% change) risk patients. Correspondingly, the decreasing utilization of BT was most pronounced among low risk patients (7% decrease) versus intermediate (3% decrease) and high (2% decrease) risk patients. The utilization of BT + EBRT remained relatively stable among low (1% decrease), intermediate (0% change), and high (2% increase) risk patients. Conclusions: This patterns of care analysis reveals decreasing utilization of brachytherapy relative to external beam radiation therapy, which is most pronounced among lower risk patients. Although our analysis did not address the cause of this trend, we hypothesize that it may be the result of changing patient/physician preference, lack of emphasis on brachytherapy during radiation oncology training, and/or physician reimbursement/selfreferral. Author Disclosure: U. Mahmood: None. M. Koshy: None. T. Pugh: None. K. Hoffman: None. D. Kuban: None. A. Lee: None.
2481 Intraprostatic Boost Using High-dose-rate Brachytherapy (HDR-BT) According to Gross Tumor Volume (GTV) Location for Prostate Cancer: A Dosimetric Feasibility Study J. Helou,1 R. Verstraet,2 P. Blanchard,1 A. Rodriguez,2 J. Bourhis,1 D. Lefkopoulos,2 L. Calmels,2 F. Azoury,1 and A. Bossi1; 1Institut Gustave Roussy, Radiation Oncology department, Villejuif, France, 2Institut Gustave Roussy, Medical Physics department, Villejuif, France
S400
International Journal of Radiation Oncology Biology Physics
Purpose/Objective(s): HDR-BT allows for dose escalation to the whole prostatic gland volume and for a selective intra-prostatic GTV boost. Short and long term urethral and rectal toxicity may limit intra-prostatic dose escalation. Our study aims to identify the dosimetric feasibility and limitations of an intra-prostatic boost to different GTVs locations according to 4 dose levels. Materials/Methods: The study was conducted on 18 patients treated on an institutional protocol of combined HDR-BT single fraction of 9.5 Gy (Z Prescribed dose, PD) followed by EBRT delivered with Intensity modulated technique (IMRT) to a total dose of 46 Gy to the seminal vesicles and 60 Gy to the prostate alone (Z CTV). The GTV locations studied for the intra-prostatic boost were; postero-lateral, total posterior, antero-lateral, total anterior and 3 volumes in the apical zone characterized by different heights in the apex-base direction: 15, 20 and 25 mm. All patients had a standard optimization with the 90% of the CTV receiving 100 to 105% of the PD. The intra-prostatic boostdose levels studied were 100%, 120%, 135% and 150% of the PD. For every boost-dose level, we reported the D90%, V100%, 120%, 150% and 200% of the CTVand of the GTV, as well as the rectal and urethral D0.1cc and D0.5cc. Results: The D90 was 100% regardless of the boost location and dose. An intraprostatic dose escalation on the postero-lateral GTV had no significant impact on the urethral D0.1cc and D0.5cc, while a significant increase in the rectal D0.1cc (74, 77, 80 and 84% for every dose level respectively) and D0.5cc (68, 70, 72 and 75%) was noted (p < 0.05). Similarly, a boost on the total posterior GTV had a significant impact on the rectal D0.1cc (74, 77, 78 and 81%) and D0.5cc (67, 70, 71 and 73%) (p < 0.05), while the urethral D0.1cc increased significantly only for a boost of 150% (p Z 0.013). An antero-lateral and total anterior boost significantly increased the urethral D0.1cc for a dose 135% (p Z 0.007 and 0.01 respectively) while significantly decreasing the rectal doses. No significant impact of an apical dose escalation was seen on the urethra whereas the rectal doses increased significantly for a boost 135% (p < 0.05). No major increase on rectal and urethral doses was observed with the 120% boost level except for the posterior GTV (D0.1cc Z 77%). However, this increase is still within acceptable limits. Conclusion: Our data show that delivering an intra-prostatic boost of 120% of the PD is safe regardless of the GTV location. Further increases of the intra-prostatic boost dose may be possible only by carefully evaluating the spatial distribution of the GTV as well as the rectal and urethral doses. Author Disclosure: J. Helou: None. R. Verstraet: None. P. Blanchard: None. A. Rodriguez: None. J. Bourhis: None. D. Lefkopoulos: None. L. Calmels: None. F. Azoury: None. A. Bossi: None.
inhibitors (5AP), and phosphodiesterase inhibitors. Pts were followed from 2 to 17.5 years (median 6). Pre-treatment PSA was 0.3 - 300 ng/mL (median 6.6). Gleason scores were 6 in 62.4%, 7 in 25.8%, and 8-10 in 11.8%. Pts were divided into NCCN risk categories of low in 45.3%, intermediate in 37.2%, and high in 17.4%. Assuming an alpha beta ratio of 2, patients were treated with a BED of 99.5-320 Gy2 (median 202.6 Gy2). Phoenix definition of PSA failure was used. Results: The overall freedom from PSA failure (FPF) at 12 years for those on a medication versus not were 85.7% vs. 84.4% for ACE/ARB (p Z 0.04); 61.8% vs. 85.2% for folic acid (p Z 0.02); and 74% vs. 84.9% for 5AP (p Z 0.01). No individual medication appeared to confer an overall or cause specific survival advantage at 12 years. ACE/ARB use continued to show a positive significant effect (p Z 0.004) and Folate use a negative effect (p < 0.0001) on FPF in Cox regression with the covariates of Hormone use, Gleason score, initial PSA, NCCN risk category, total BED, and 5AP use. In contrast, 5AP lost its significant effect on FPF in multivariable analysis. Conclusions: AB appears to confer a FPF advantage for pts receiving definitive radiation, while Folate supplementation portends a worse FPF. These findings are hypothesis generating, suggest a potential role for adjusting medication subtype during treatment, and call for further research to elucidate their possible mechanism of action during definitive radiation therapy for PC. Author Disclosure: S.R. Blacksburg: None. E.C. Ko: None. N.N. Stone: E. Research Grant; DOD, NIH. G. Consultant; Amgen, Bayer, DCMI, Ferring, Centacor Biotech. P. Ownership Other; Prologics LLC. R.G. Stock: None.
2482 The Potential Impact of Medications on Biochemical Control Following Definitive Management of Prostate Cancer S.R. Blacksburg, E.C. Ko, N.N. Stone, and R.G. Stock; Mount Sinai Medical Center, New York, NY Purpose: A growing body of literature has demonstrated the impact of medication on the incidence and all cause mortality related to prostate cancer (PC). This has been demonstrated through pre-clinical studies, the Cancer of the Prostate Strategic Urologic Research Endeavor database, as well as numerous meta-analyses. Folate supplementation has been associated with increased incidence of PC and the modulation of angiotensin II blockade (AB) has been implicated in reduced PC incidence and all cause mortality risk. However, the role of medication on treatment-related outcome is lacking. The potential effect of these medications on biochemical control following definitive radiation for PC was analyzed. Material and Methods: A total of 1,912 PC patients (pts) were treated with definitive radiation, including external beam radiation and low dose rate brachytherapy regimens, from 1990 through 2010. Classes of medication documented included calcium channel blockers, statins, beta blockers, ACE-inhibitors/angiotensin receptor blockers (ACE/ARB), folic acid, proton pump inhibitors, alpha-1 adrenergic blockers, HIV medication, metformin and oral hypoglycemics, histamine blockers, non-steroidal antiinflammatory drugs, steroids, selective serotonin reuptake inhibitors, insulin, aspirin, warfarin, clopidogrel, diuretics, 5-alpha reductase
2483 What Daily Image Guidance Is Needed for Prostate Cancer Patients Post Radical Prostatectomy? Data From a Pilot Phase II Study T.M. Niazi, B. Bahoric, N. Tomic, and T. Vuong; Segal Cancer Centre, Jewish General Hospital. McGill University, Montreal, QC, Canada Purpose/Objective(s): Image guided Radiation Therapy (RT) for prostate cancer patients is becoming the norm in developed countries. For prostate in place ultrasound and Cone Beam Computed Tomography (CBCT) are the two commonly used target localizing modalities, while KvKv (orthogonal) images and CBCT can be used for patients requiring salvage or adjuvant radiation therapy post radical prostatectomy (RP). In this study we assessed if Kv-Kv localization images are sufficient for patients requiring adjuvant or salvage RT. Materials/Methods: As per our standard of care all prostate cancer patients, requiring adjuvant or salvager RT, undergo CBCT for target localization. Twenty-four such patients, with radio-opaque surgical clips, agreed to participate into this phase II study. After informed written consent, these patients underwent two orthogonal Kv-Kv images prior to the routine CBCT at each RT fraction. Treatment target volumes were initially localized using the Kv-Kv images, however, the final treatment was based on the CBCT 3-dimensional shifts (vertical, lateral and longitudinal). For each patient the Kv-Kv shifts were than compared with CBCT at each fraction and a mean value was obtained. The mean values of the two approaches were then analyzed, individually and collectively. Results: Twenty-four prostate cancer patients, requiring post RP salvage or adjuvant RT, took part into this prospective study. The mean shift, after Kv-Kv localization, was 0.18 cm laterally, 0.23 cm vertically, and 0.21 cm longitudinally with respective standard deviation (SD) of: 0.12; 0.1 and 0.11. However, the mean for the maximum difference in the treatment shifts were 0.6 cm, 0.61 cm and 0.68 cm respectively with SD of 0.45, 0.30 and 0.48 respectively. Individual dimensional analysis revealed maximum shifts of up to 1.5 cm. Conclusions: From the cumulative mean values, magnitude of the difference averaged over all treatment fractions, the difference between CBCT and Kv-Kv, using clips, is less than 5 mm. However, the difference for the maximum shift could be up to 1.5 cm in one direction. Therefore, we conclude that CBCT is the superior imaging modality that uses soft tissue to align with target contour in 3D and it is the most accurate as compared to Kv-Kv.