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COX-2 Expression Does Not Predict Biochemical Failure in Patients Treated with Salvage Radiation Therapy for Prostate Cancer
I. J. Radiation Oncology d Biology d Physics
S410
Volume 81, Number 2, Supplement, 2011
Materials/Methods: Between 1994 and 2007, 1649 men received external beam radiotherapy (RT) alone (median dose = 76 Gy). All men underwent transrectal ultrasound-guided biopsy of the prostate before RT. All slides for cases diagnosed in RI were reviewed at FCCC. Most cases were examined by an oncologic pathologist with a special experience in urologic pathology. Cases with discrepancy in grading with the RI were examined by two or more oncologic pathologists until a consensus diagnosis was reached. The Kappa coefficient (k) was used to examine the agreement between FCCC and RI GS (including major and minor patterns). k of 1 indicates perfect agreement, whereas k of 0 indicates agreement no better than chance. Risk of BF was examined using Cox proportional hazards multivariable analyses (MVA) with FCCC GS and RI GS separately, each model adjusting for T-stage (T1-2 v T3/4), initial PSA (continuous) and RT dose (continuous). Harrell’s C-index (HCI) was used to assess concordance in the Cox regression between predicted and observed events. HCI of 1 indicates a perfect ability to rank the outcomes in the order they actually occurred, whereas 0.5 is a purely random ranking; this value is comparable to the area under the receiver operator characteristic curve. Results: RI GS were distributed 69% GS 2-6, 16% GS 3+4, 11% GS 4+3, and 4% GS 8-9. Compared to RI GS, FCCC GS was upgraded in 14% of patients and downgraded in 12%, based on change in major/minor pattern. Agreement between FCCC and RI GS was moderate, k = 0.53, (95% CI 0.50-0.57). FCCC GS had improved performance to RI GS, HCI = 0.76 vs. 0.74. FCCC GS (p\0.0001) was a strong predictor of BF in the MVA; Hazard Ratio (HR) estimates for FCCC GS 2-6 (ref), 3+4, 4+3 and 8-9 were 1.00 (ref), 1.82, 4.14 and 2.92 (HR for 4+3 vs 3+4 was 2.27, p\0.0001). In the model using RI GS (p\0.0001), corresponding HR estimates were 1.00 (ref), 1.53, 2.44 and 1.76. (HR for 4+3 vs 3+4 was 1.59, p = 0.037). Upgraded GS (HR = 1.58, 95% CI 1.112.24, p = 0.011) and downgraded GS (HR = 0.41, 95% CI 0.25-0.67, p = 0.0004) were independent predictors of BF in a model also including RI GS. Conclusions: FCCC upgrading or downgrading of RI GS was a strong independent predictor of BF. FCCC GS showed a notable difference between 4+3 versus 3+4 for BF risk. This is an example of how a second opinion at a comprehensive cancer center may alter treatment recommendations and improves the patient’s knowledge of his prognosis. Validation of these findings at other centers is warranted. Author Disclosure: N.C. Townsend: None. K. Ruth: None. T. Al-Saleem: None. E.M. Horwitz: None. M. Sobczak: None. R.G. Uzzo: None. R. Viterbo: None. M.K. Buyyounouski: None.
2416
Dynamic Contrast Enhanced MRI for the Identification of Prostate Cancer in the Prostate Bed After Radical Prostatectomy
M. C. Abramowitz, R. Stoyanova, B. Kava, M. Soloway, M. Manoharan, J. Casillas, A. Pollack University of Miami, Miami, FL Purpose/Objective(s): The delivery of high doses of radiation to the entire prostate bed is somewhat limited due to the presence of the bladder and rectum. Dose escalation data in the post-prostatectomy setting suggests that local control is suboptimal and related to tumor burden. If regions in the prostate bed could be identified, then higher than standard doses could be directed to the smaller volumes with less potential long term morbidity. DCE MRI can be utilized to identify tumor associated new angiogenic blood vessels. This has been shown to have a higher sensitivity than T2 weighted MRI images alone. We applied this technology to 34 men with an elevated PSA after radical surgery and evaluated enhancement patterns to identify residual or recurrent disease. Materials/Methods: 33 patients who were referred for RT consultation at the University of Miami from 6/1/2008 to 1/21/2011 were prospectively evaluated. The DCE-MRI data were acquired on a 3T MR scanner (Siemens Trio Tim, Erlangen, Germany). T2 and T1 MR images were acquired prior to contrast material injection followed by 11-12 post-contrast image sets. The DCE data were analyzed with in-house software, utilizing pattern recognition techniques for deconvolution of the contrast-to-time patterns. Identified areas in the prostate bed were scored as positive only if there was early contrast wash in and then wash-out in a characteristic pattern. Results: Out of the 33 pts, 14 (42%) were positive in the prostate bed. The median age of the patients presenting for RT was 63 years (43 - 79). Nine patients (26%) had a prostatectomy Gleason Score (GS) of 6, 13 (38%) had a GS of 7, 7 (20%) had a GS of 8, and 5 (15%) had a GS of 9. The average pre-RT PSA was 1.16 (0.1 - 9.2); 0.96 (median 0.33) for MRI (-) Pts and 1.8 (median 0.5) for MRI (+). For MRI (-) pts the median interval between surgery and radiation was 2.7 yrs and 2.54 yrs for MRI (+). Of the MRI(+) pts 6 (43%) were T2, 5 (36%) T3a, 2 (14%)T3b and 1 (7%) T4. Of the MRI(-) pts 11 (58%) were T2, 4 (21%) T3a, 4 (21%)T3b and 0 (0%) T4. Due to small numbers these differences were not statistically significant. Conclusions: Our data indicate that MRI, combined with DCE detects abnormalities suggestive of residual tumor in the prostate bed in 42% of patients evaluated for RT. This suggests a substantial amount of disease for which standard doses of salvage radiation may be inadequate. By limiting the high dose of radiation only to the gross disease, we may improve our therapeutic index. Author Disclosure: M.C. Abramowitz: None. R. Stoyanova: None. B. Kava: None. M. Soloway: None. M. Manoharan: None. J. Casillas: None. A. Pollack: None.
2417
COX-2 Expression Does Not Predict Biochemical Failure in Patients Treated with Salvage Radiation Therapy for Prostate Cancer
K. S. Tzou1, S. J. Buskirk1, M. G. Heckman1, A. S. Parker1, V. Patel2, L. Pelaez2, T. W. Hilton1, J. L. Peterson1, L. A. Vallow1, A. Pollack2 1
Mayo Clinic Florida, Jacksonville, FL, 2University of Miami, Miami, FL
Purpose/Objective(s): Evidence in the literature suggests that high expression of cyclooxygenase-2 (COX-2) in prostate tumor tissue is associated with increased biochemical failure (BCF), distant metastasis, and any failure after definitive
Proceedings of the 53rd Annual ASTRO Meeting external beam radiation therapy (EBRT). To date, there are no published data regarding whether higher COX-2 levels are associated with increased risk of BCF following salvage radiation therapy (SRT) for prostate cancer. We sought to evaluate COX-2 expression in radical prostatectomy (RP) specimens and its association with BCF in men treated with SRT for a detectable PSA after RP. Materials/Methods: We identified 151 men with prostate cancer treated with SRT for a detectable PSA after RP between July 1987 to July 2003 at Mayo Clinic Florida, and for whom we had sufficient diagnostic tissue available for immunohistochemical staining and image analysis of COX-2 expression. Staining levels of COX-2 were detected by monoclonal antibody and quantified by an automated imaging system. COX-2 staining intensity was initially recorded as a numerical variable, and then categorized into 3 levels based on sample tertiles: low (\115), moderate (115-130), and high (.130). Relative risks (RRs) and 95% confidence intervals (CIs) from Cox proportional hazards models were used to evaluate the association between COX-2 staining intensity and the primary endpoint of BCF (PSA $ 0.4 ng/mL post-SRT and rising), in single variable models and after multivariable adjustment. Results: Median follow-up was 4.6 years. The estimated incidence of BCF at 8 years was 57%, 62%, and 47.9% in the low, moderate, and high COX-2 intensity groups, respectively. We observed no evidence of an association between COX-2 intensity and BCF when considering COX-2 as a continuous variable (RR: 0.81 [25 unit increase], 95% CI: 0.63 - 1.05, P = 0.11), or as the aforementioned three-level categorical variable (RR [moderate vs. low]: 1.11, 95% CI: 0.66 - 1.86, P = 0.69; RR [high vs. low]: 0.71, 95% CI: 0.42 - 1.18, P = 0.18). These results remained consistent in multivariable analysis adjusting for pathologic tumor stage, Gleason score, pre-SRT PSA, pre-RP PSA, SRT dose, age, time from RP to initiation of SRT, margin status, pre-SRT hormone therapy, and year of start of SRT. Conclusions: This is the first study to examine the association of COX-2 expression in prostate cancer and patient outcomes after SRT. Although COX-2 overexpression has been associated with an increased risk of BCF after definitive prostate cancer EBRT plus hormone therapy, our data did not show any significant association between COX-2 expression and the risk of BCF after radiation in the salvage setting. If confirmed, COX-2 is not likely to be useful as a biomarker for predicting which men will benefit most from SRT. Author Disclosure: K.S. Tzou: None. S.J. Buskirk: None. M.G. Heckman: None. A.S. Parker: None. V. Patel: None. L. Pelaez: None. T.W. Hilton: None. J.L. Peterson: None. L.A. Vallow: None. A. Pollack: None.
2418
Prospective Pilot Trial of Daily Vitamin D Supplementation in the Active Surveillance of Low-Risk Prostate Cancer
L. Cannick, D. T. Marshall, S. J. Savage, E. Garrett-Mayer, L. H. Ambrose, S. Gattoni-Celli Medical University of South Carolina, Charleston, SC Purpose/Objective(s): Vitamin D inhibits the stress-activated protein kinase p38, an activator of the pro-inflammatory cytokine interleukin 6, implicated in the initiation and progression of prostate cancer. The specific aims of this study are to: 1) determine if daily doses of vitamin D3 (VD3) at 4,000 IU by mouth, taken for at least 12 months, are safe and will result in decreased PSA levels in patients with low risk prostate cancer on active surveillance, and 2) compare percent positive cores from biopsies done before and after treatment with VD3. Materials/Methods: 52 patients(pts) with early stage low risk prostate cancer, serum PSA value #10.0 ng/ml, and a Gleason score of 6 or less, clinical stage \T2b, have been enrolled in this IRB approved pilot study. All pts are monitored via active surveillance for at least one year, which includes routine labs every 8 weeks and a prostate biopsy recommended 12 months after the initial biopsy. Patients are given 4,000 IU orally of VD3 each day. Upon completion of the protocol pts may elect to continue active surveillance or proceed to definitive treatment. The total planned sample size was 80 pts. The study was closed to accrual in September 2010 due to the start of a competing randomized trial testing VD3 versus placebo in active surveillance for low risk prostate cancer pts. Results: From October 2007 to September 2010, 52 pts were enrolled: 14 African America (AA), 37 white (CC), and 1 Asian. Three pts were withdrawn from the study. For pts with baseline VD3 levels\20ng/ml (severely deficient) the median pre-treatment PSA was 5.65 (n = 11), and for subjects with baseline VD3 levels .20ng/ml their median PSA was 4.07 (n = 41). The average baseline VD3 levels by race were AA 23.89ng/ml (n = 14), and CC 36.56ng/ml (n = 37), (p = 0.002). VD3 levels for all pts rose above 20-ng/ml after only 8 weeks of supplementation. With 11.1 months median follow-up, there have been no toxicities associated with the trial. For the 33 pts that have completed the study, there has been an objective decrease in the overall number of positive cores, with no correlation to changes in PSA. Conclusions: These encouraging preliminary observations reveal no adverse effects from the use of 4,000 IU of VD3 daily with .11 months follow-up. Baseline VD3 levels were lower in AA prostate cancer pts than in CC pts. 8 weeks of oral supplementation is sufficient to achieve levels above 20ng/ml. The use of VD3 supplementation may decrease the volume of prostate cancer as seen on repeat biopsy in these pts with low risk disease on active surveillance. Final results will be analyzed when all enrolled pts have completed the study in August of 2011. Author Disclosure: L. Cannick: None. D.T. Marshall: None. S.J. Savage: None. E. Garrett-Mayer: None. L.H. Ambrose: None. S. Gattoni-Celli: None.
2419
Is Alpha/Beta Value of Linear-Quadratic Model Dependent on Histologic Grade in Prostate Cancer?
1,2
Y. Seo , K. Konishi2, M. Morimoto2, F. Isohashi2, T. Ogata2, Y. Takahashi2, I. Sumida2, M. Koizumi2, Y. Yoshioka2 1
Kaizuka City Hospital, Osaka, Japan, 2Osaka University Graduate School of Medicine, Osaka, Japan
Purpose/Objective(s): Multiple studies have shown that an alpha/beta value of a linear-quadratic (LQ) model is much lower in prostate cancer than that in most rapidly growing tumors. However, it is unknown whether the alpha/beta values differ depending on a histologic grade in prostate cancer.
S411
S410
Volume 81, Number 2, Supplement, 2011
Materials/Methods: Between 1994 and 2007, 1649 men received external beam radiotherapy (RT) alone (median dose = 76 Gy). All men underwent transrectal ultrasound-guided biopsy of the prostate before RT. All slides for cases diagnosed in RI were reviewed at FCCC. Most cases were examined by an oncologic pathologist with a special experience in urologic pathology. Cases with discrepancy in grading with the RI were examined by two or more oncologic pathologists until a consensus diagnosis was reached. The Kappa coefficient (k) was used to examine the agreement between FCCC and RI GS (including major and minor patterns). k of 1 indicates perfect agreement, whereas k of 0 indicates agreement no better than chance. Risk of BF was examined using Cox proportional hazards multivariable analyses (MVA) with FCCC GS and RI GS separately, each model adjusting for T-stage (T1-2 v T3/4), initial PSA (continuous) and RT dose (continuous). Harrell’s C-index (HCI) was used to assess concordance in the Cox regression between predicted and observed events. HCI of 1 indicates a perfect ability to rank the outcomes in the order they actually occurred, whereas 0.5 is a purely random ranking; this value is comparable to the area under the receiver operator characteristic curve. Results: RI GS were distributed 69% GS 2-6, 16% GS 3+4, 11% GS 4+3, and 4% GS 8-9. Compared to RI GS, FCCC GS was upgraded in 14% of patients and downgraded in 12%, based on change in major/minor pattern. Agreement between FCCC and RI GS was moderate, k = 0.53, (95% CI 0.50-0.57). FCCC GS had improved performance to RI GS, HCI = 0.76 vs. 0.74. FCCC GS (p\0.0001) was a strong predictor of BF in the MVA; Hazard Ratio (HR) estimates for FCCC GS 2-6 (ref), 3+4, 4+3 and 8-9 were 1.00 (ref), 1.82, 4.14 and 2.92 (HR for 4+3 vs 3+4 was 2.27, p\0.0001). In the model using RI GS (p\0.0001), corresponding HR estimates were 1.00 (ref), 1.53, 2.44 and 1.76. (HR for 4+3 vs 3+4 was 1.59, p = 0.037). Upgraded GS (HR = 1.58, 95% CI 1.112.24, p = 0.011) and downgraded GS (HR = 0.41, 95% CI 0.25-0.67, p = 0.0004) were independent predictors of BF in a model also including RI GS. Conclusions: FCCC upgrading or downgrading of RI GS was a strong independent predictor of BF. FCCC GS showed a notable difference between 4+3 versus 3+4 for BF risk. This is an example of how a second opinion at a comprehensive cancer center may alter treatment recommendations and improves the patient’s knowledge of his prognosis. Validation of these findings at other centers is warranted. Author Disclosure: N.C. Townsend: None. K. Ruth: None. T. Al-Saleem: None. E.M. Horwitz: None. M. Sobczak: None. R.G. Uzzo: None. R. Viterbo: None. M.K. Buyyounouski: None.
2416
Dynamic Contrast Enhanced MRI for the Identification of Prostate Cancer in the Prostate Bed After Radical Prostatectomy
M. C. Abramowitz, R. Stoyanova, B. Kava, M. Soloway, M. Manoharan, J. Casillas, A. Pollack University of Miami, Miami, FL Purpose/Objective(s): The delivery of high doses of radiation to the entire prostate bed is somewhat limited due to the presence of the bladder and rectum. Dose escalation data in the post-prostatectomy setting suggests that local control is suboptimal and related to tumor burden. If regions in the prostate bed could be identified, then higher than standard doses could be directed to the smaller volumes with less potential long term morbidity. DCE MRI can be utilized to identify tumor associated new angiogenic blood vessels. This has been shown to have a higher sensitivity than T2 weighted MRI images alone. We applied this technology to 34 men with an elevated PSA after radical surgery and evaluated enhancement patterns to identify residual or recurrent disease. Materials/Methods: 33 patients who were referred for RT consultation at the University of Miami from 6/1/2008 to 1/21/2011 were prospectively evaluated. The DCE-MRI data were acquired on a 3T MR scanner (Siemens Trio Tim, Erlangen, Germany). T2 and T1 MR images were acquired prior to contrast material injection followed by 11-12 post-contrast image sets. The DCE data were analyzed with in-house software, utilizing pattern recognition techniques for deconvolution of the contrast-to-time patterns. Identified areas in the prostate bed were scored as positive only if there was early contrast wash in and then wash-out in a characteristic pattern. Results: Out of the 33 pts, 14 (42%) were positive in the prostate bed. The median age of the patients presenting for RT was 63 years (43 - 79). Nine patients (26%) had a prostatectomy Gleason Score (GS) of 6, 13 (38%) had a GS of 7, 7 (20%) had a GS of 8, and 5 (15%) had a GS of 9. The average pre-RT PSA was 1.16 (0.1 - 9.2); 0.96 (median 0.33) for MRI (-) Pts and 1.8 (median 0.5) for MRI (+). For MRI (-) pts the median interval between surgery and radiation was 2.7 yrs and 2.54 yrs for MRI (+). Of the MRI(+) pts 6 (43%) were T2, 5 (36%) T3a, 2 (14%)T3b and 1 (7%) T4. Of the MRI(-) pts 11 (58%) were T2, 4 (21%) T3a, 4 (21%)T3b and 0 (0%) T4. Due to small numbers these differences were not statistically significant. Conclusions: Our data indicate that MRI, combined with DCE detects abnormalities suggestive of residual tumor in the prostate bed in 42% of patients evaluated for RT. This suggests a substantial amount of disease for which standard doses of salvage radiation may be inadequate. By limiting the high dose of radiation only to the gross disease, we may improve our therapeutic index. Author Disclosure: M.C. Abramowitz: None. R. Stoyanova: None. B. Kava: None. M. Soloway: None. M. Manoharan: None. J. Casillas: None. A. Pollack: None.
2417
COX-2 Expression Does Not Predict Biochemical Failure in Patients Treated with Salvage Radiation Therapy for Prostate Cancer
K. S. Tzou1, S. J. Buskirk1, M. G. Heckman1, A. S. Parker1, V. Patel2, L. Pelaez2, T. W. Hilton1, J. L. Peterson1, L. A. Vallow1, A. Pollack2 1
Mayo Clinic Florida, Jacksonville, FL, 2University of Miami, Miami, FL
Purpose/Objective(s): Evidence in the literature suggests that high expression of cyclooxygenase-2 (COX-2) in prostate tumor tissue is associated with increased biochemical failure (BCF), distant metastasis, and any failure after definitive
Proceedings of the 53rd Annual ASTRO Meeting external beam radiation therapy (EBRT). To date, there are no published data regarding whether higher COX-2 levels are associated with increased risk of BCF following salvage radiation therapy (SRT) for prostate cancer. We sought to evaluate COX-2 expression in radical prostatectomy (RP) specimens and its association with BCF in men treated with SRT for a detectable PSA after RP. Materials/Methods: We identified 151 men with prostate cancer treated with SRT for a detectable PSA after RP between July 1987 to July 2003 at Mayo Clinic Florida, and for whom we had sufficient diagnostic tissue available for immunohistochemical staining and image analysis of COX-2 expression. Staining levels of COX-2 were detected by monoclonal antibody and quantified by an automated imaging system. COX-2 staining intensity was initially recorded as a numerical variable, and then categorized into 3 levels based on sample tertiles: low (\115), moderate (115-130), and high (.130). Relative risks (RRs) and 95% confidence intervals (CIs) from Cox proportional hazards models were used to evaluate the association between COX-2 staining intensity and the primary endpoint of BCF (PSA $ 0.4 ng/mL post-SRT and rising), in single variable models and after multivariable adjustment. Results: Median follow-up was 4.6 years. The estimated incidence of BCF at 8 years was 57%, 62%, and 47.9% in the low, moderate, and high COX-2 intensity groups, respectively. We observed no evidence of an association between COX-2 intensity and BCF when considering COX-2 as a continuous variable (RR: 0.81 [25 unit increase], 95% CI: 0.63 - 1.05, P = 0.11), or as the aforementioned three-level categorical variable (RR [moderate vs. low]: 1.11, 95% CI: 0.66 - 1.86, P = 0.69; RR [high vs. low]: 0.71, 95% CI: 0.42 - 1.18, P = 0.18). These results remained consistent in multivariable analysis adjusting for pathologic tumor stage, Gleason score, pre-SRT PSA, pre-RP PSA, SRT dose, age, time from RP to initiation of SRT, margin status, pre-SRT hormone therapy, and year of start of SRT. Conclusions: This is the first study to examine the association of COX-2 expression in prostate cancer and patient outcomes after SRT. Although COX-2 overexpression has been associated with an increased risk of BCF after definitive prostate cancer EBRT plus hormone therapy, our data did not show any significant association between COX-2 expression and the risk of BCF after radiation in the salvage setting. If confirmed, COX-2 is not likely to be useful as a biomarker for predicting which men will benefit most from SRT. Author Disclosure: K.S. Tzou: None. S.J. Buskirk: None. M.G. Heckman: None. A.S. Parker: None. V. Patel: None. L. Pelaez: None. T.W. Hilton: None. J.L. Peterson: None. L.A. Vallow: None. A. Pollack: None.
2418
Prospective Pilot Trial of Daily Vitamin D Supplementation in the Active Surveillance of Low-Risk Prostate Cancer
L. Cannick, D. T. Marshall, S. J. Savage, E. Garrett-Mayer, L. H. Ambrose, S. Gattoni-Celli Medical University of South Carolina, Charleston, SC Purpose/Objective(s): Vitamin D inhibits the stress-activated protein kinase p38, an activator of the pro-inflammatory cytokine interleukin 6, implicated in the initiation and progression of prostate cancer. The specific aims of this study are to: 1) determine if daily doses of vitamin D3 (VD3) at 4,000 IU by mouth, taken for at least 12 months, are safe and will result in decreased PSA levels in patients with low risk prostate cancer on active surveillance, and 2) compare percent positive cores from biopsies done before and after treatment with VD3. Materials/Methods: 52 patients(pts) with early stage low risk prostate cancer, serum PSA value #10.0 ng/ml, and a Gleason score of 6 or less, clinical stage \T2b, have been enrolled in this IRB approved pilot study. All pts are monitored via active surveillance for at least one year, which includes routine labs every 8 weeks and a prostate biopsy recommended 12 months after the initial biopsy. Patients are given 4,000 IU orally of VD3 each day. Upon completion of the protocol pts may elect to continue active surveillance or proceed to definitive treatment. The total planned sample size was 80 pts. The study was closed to accrual in September 2010 due to the start of a competing randomized trial testing VD3 versus placebo in active surveillance for low risk prostate cancer pts. Results: From October 2007 to September 2010, 52 pts were enrolled: 14 African America (AA), 37 white (CC), and 1 Asian. Three pts were withdrawn from the study. For pts with baseline VD3 levels\20ng/ml (severely deficient) the median pre-treatment PSA was 5.65 (n = 11), and for subjects with baseline VD3 levels .20ng/ml their median PSA was 4.07 (n = 41). The average baseline VD3 levels by race were AA 23.89ng/ml (n = 14), and CC 36.56ng/ml (n = 37), (p = 0.002). VD3 levels for all pts rose above 20-ng/ml after only 8 weeks of supplementation. With 11.1 months median follow-up, there have been no toxicities associated with the trial. For the 33 pts that have completed the study, there has been an objective decrease in the overall number of positive cores, with no correlation to changes in PSA. Conclusions: These encouraging preliminary observations reveal no adverse effects from the use of 4,000 IU of VD3 daily with .11 months follow-up. Baseline VD3 levels were lower in AA prostate cancer pts than in CC pts. 8 weeks of oral supplementation is sufficient to achieve levels above 20ng/ml. The use of VD3 supplementation may decrease the volume of prostate cancer as seen on repeat biopsy in these pts with low risk disease on active surveillance. Final results will be analyzed when all enrolled pts have completed the study in August of 2011. Author Disclosure: L. Cannick: None. D.T. Marshall: None. S.J. Savage: None. E. Garrett-Mayer: None. L.H. Ambrose: None. S. Gattoni-Celli: None.
2419
Is Alpha/Beta Value of Linear-Quadratic Model Dependent on Histologic Grade in Prostate Cancer?
1,2
Y. Seo , K. Konishi2, M. Morimoto2, F. Isohashi2, T. Ogata2, Y. Takahashi2, I. Sumida2, M. Koizumi2, Y. Yoshioka2 1
Kaizuka City Hospital, Osaka, Japan, 2Osaka University Graduate School of Medicine, Osaka, Japan
Purpose/Objective(s): Multiple studies have shown that an alpha/beta value of a linear-quadratic (LQ) model is much lower in prostate cancer than that in most rapidly growing tumors. However, it is unknown whether the alpha/beta values differ depending on a histologic grade in prostate cancer.
S411