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Factors Predicting Outcome for Intermediate-Risk Prostate Cancer Patients Undergoing I-125 Brachytherapy With or Without External Beam Radiation Therapy
Volume 99 Number 2S Supplement 2017 C.J. Beard,7 Q.D. Trinh,8 and P.L. Nguyen4; 1Harvard Medical School, Boston, MA, 2Harvard Radiation Oncology Program, Harvard Medical School, Boston, MA, 3Brigham and Women’s Hospital, Boston, MA, 4 Department of Radiation Oncology, Dana-Farber Cancer Institute and Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, 5 Stanford University, Stanford, CA, 6Department of R, Boston, MA, 7 Department of Radiation Oncology, Brigham and Women’s Hospital, Boston, MA, 8Center for Surgery and Public Health and Division of Urological Surgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA Purpose/Objective(s): Whether active surveillance can be safely offered to patients with intermediate-risk prostate cancer, particularly those with Gleason 3+4 favorable intermediate-risk (FIR) disease, is unknown. We studied this question by examining the incidence and predictors of upgrading and upstaging among patients with Gleason 3+4 FIR disease. Materials/Methods: We identified 10,089 patients in the National Cancer Database diagnosed from 2010 through 2012 with Gleason 3+4, PSA<10 ng/mL, and cT1c-2a prostate cancer with <50% positive biopsy cores (PBC) without clinical evidence of nodal or metastatic disease who were treated with radical prostatectomy. Multiple logistic regression was used to examine factors associated with upgrading (pathological Gleason 4+3 or 810) or upstaging (pT3-4 or pN1). Results: 27.7% of all Gleason 3+4 FIR patients (2,793) were upgraded or upstaged (15.6% upgraded and 17.0% upstaged). On multivariable analysis, predictors of upgrading or upstaging include higher PSA, percentage of PBC, and cT stage, as well as older age (p<0.001 for all), but not Black race (pZ0.651). When stratified into ordinal variables, PSA 8.1-9.9 ng/mL vs. 2.1-4.0 ng/mL (AOR 1.98, 34.9% vs. 21.4%); 37.5-49.9% vs. <12.5% PBC (AOR 1.77, 34.2% vs. 22.4%); cT2a vs. cT1c stage (AOR 1.32, 31.8% vs 27.1%); and highest quartile age (67) vs. lowest (55; AOR 1.45, 32.7% vs. 22.3%) were associated with increased risk of upstaging or upgrading (p<0.001 for all). 40.3% of men age 67 with 37.5-49.9% PBC were upgraded or upstaged. Conclusion: Overall, just over 1 in 4 Gleason 3+4 FIR patients were upgraded or upstaged after radical prostatectomy. Younger patients with low PBC, low PSA, and cT1c stage have a lower risk of harboring higher grade or stage disease and may be candidates for active surveillance. However, models based on widely available clinical information are insufficient for predicting the risk of more advanced disease, and research is necessary into developing and incorporating additional tools, including magnetic resonance imaging and genomic tests. Author Disclosure: D.D. Yang: None. B.A. Mahal: None. V. Muralidhar: None. M.D. Nezolosky: None. M. Vastola: None. S. Labe: None. N. Boldbaatar: None. M. King: None. N.E. Martin: Consultant; Via Oncology. P.F. Orio: Honoraria; CR BARD. Consultant; Augmenix. ; American Brachytherapy Society, ASTRO. C.J. Beard: None. Q. Trinh: None. P.L. Nguyen: Consultant; GI Windows, Infinity Pharmaceuticals, Nanobiotix. Advisory Board; Dendreon, Ferring, Genome DX, Medivation. ; Genitourinary Cancers Symposium.
2661 Androgen Deprivation Therapy and Elevated Risk of Rheumatoid Arthritis in Patients With Prostate Cancer D.D. Yang,1 A. Krasnova,2 K.T. Nead,3 Q.D. Trinh,4 and P.L. Nguyen5; 1 Harvard Medical School, Boston, MA, 2Center for Surgery and Public Health, Brigham and Women’s Hospital, Boston, MA, 3Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, 4 Center for Surgery and Public Health and Division of Urological Surgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, 5 Department of Radiation Oncology, Dana-Farber Cancer Institute and Brigham and Women’s Hospital, Harvard Medical School, Boston, MA Purpose/Objective(s): Testosterone is immunosuppressive, and studies have shown that men with untreated hypogonadism are at increased risk for autoimmune conditions. To date, there has been no evidence linking androgen deprivation therapy (ADT) to the development of autoimmune
Poster Viewing E277 diseases, including rheumatoid arthritis (RA). We investigated the association between ADT and RA. Materials/Methods: We identified 138,770 men age 66 years or older with stage I-III prostate cancer using the Surveillance, Epidemiology, and End Results -Medicare linked database from 1992 through 2009, excluding patients with a diagnosis of RA in the prior year. Chi-squared test was utilized to compare differences in Kaplan-Meier event rates. Cox regression using inverse probability of treatment weighting to adjust for demographic and clinical factors was used to examine the association between pharmacologic ADT and diagnosis of RA. Results: The 39.9% of patients (55,321) who received ADT experienced a higher 5-year rate of RA than patients who did not receive ADT (4.3% vs. 3.4%, p<0.001), with a number needed to harm of 110 patients. Receipt of any ADT was associated with a 23% increased risk of developing RA (hazard ratio [HR] 1.23, 95% CI 1.12-1.35, p<0.001). The risk of RA increased with a longer duration of ADT, from 17% with 1-6 months (HR 1.17, 95% CI 1.09-1.26, p<0.001) and 26% with 7-11 months (HR 1.26, 95% CI 1.09-1.45, pZ0.002) to 36% with 12 months (HR 1.36, 95% CI 1.16-1.60, p<0.001). Conclusion: ADT was associated with an elevated risk of developing RA in this large cohort of elderly men with non-metastatic prostate cancer. The risk was higher with a longer duration of ADT. Our findings are the first linking ADT to an increased risk of autoimmunity and add to mounting evidence of the many adverse effects of ADT that should prompt physicians to thoughtfully weigh its risks and benefits, particularly for intermediate-risk patients. Author Disclosure: D.D. Yang: None. A. Krasnova: None. K.T. Nead: None. Q. Trinh: None. P.L. Nguyen: Consultant; GI Windows, Infinity Pharmaceuticals, Nanobiotix. Advisory Board; Dendreon, Ferring, Genome DX, Medivation. ; Genitourinary Cancers Symposium.
2662 Factors Predicting Outcome for Intermediate-Risk Prostate Cancer Patients Undergoing I-125 Brachytherapy With or Without External Beam Radiation Therapy A. Yorozu, S. Sutani, R. Kota, S. Saito, and K. Toya; Tokyo Medical Center, Tokyo, Japan Purpose/Objective(s): To evaluate the influence of patient- and treatment-related factors on clinical outcomes in intermediate-risk prostate cancer patients undergoing I-125 brachytherapy (BT). Materials/Methods: From a prospectively collected database of 1846 men treated for prostate cancer with I-125 brachytherapy between 2003 and 2012, 1000 men with intermediate-risk features were analyzed. A total of 402 men were treated only with BT, and another 598 were treated with BT combined with external beam radiotherapy (EBRT). Low-tier intermediate-risk patients (defined as a clinical stage of T1-2, PSA level of <10 ng/ mL, and a Gleason score of 3+4 with a biopsy positive core rate of <33.4%) received BT alone. The prescription dose was 145 Gy without EBRT or 110 Gy with EBRT, and the dose to 90% of the prostate (D90) was 110e130% of the prescription dose. In combined EBRT, 45 Gy in 25 fractions was given to the prostate and seminal vesicles. Neoadjuvant androgen deprivation (NAD) was given to 414 men. Patient and treatment factors were examined for an association with clinical outcomes. Biochemical failure was determined by the Phoenix definition. Among patients with biochemical failure, local recurrence was defined as the detection of cancer by post-treatment biopsy analysis, by MRI or by digital rectal exam. Prostate-cancer-specific mortality (PCSM) and overall survival (OS) were assessed. Radiation doses were converted to the biological effective dose (BED) using an a/b ratio of 2 and the D90 values of the prostate from a day-30 CT scan. The Kaplan-Meier method and Cox regression model were used for analysis. Results: At a median follow-up of 8 years, freedom from biochemical failure (FFbF), actuarial local recurrence rate, PCSM, and OS were 91.9%, 1.3%, 1.1%, 91.5%, respectively. In univariate and multivariate analyses, a Gleason score of 4+3 was the only significant predictor of FFbF
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(pZ0.001), PCSM (p<0.01), and OS (p<0.05). None of the other variables (PSA, T-factor, positive core rate, multiple intermediate-risk factors, EBRT, NAD, or BED) was found to be statistically significant predictor of these outcomes. BED (<200 Gy2) and BT alone were significant predictors for local recurrence in univariate analysis, and BED was significant (p<0.05) in multivariate analysis. Overall, NAD did not predict FFbF (pZ0.075). In patients with a Gleason score of 4+3, FFbF was 92.9% with NAD and 84.1% without NAD (p<0.05). Conclusion: A Gleason score of 4+3 is an important predictor of FFbF, PCSM, and OS in intermediate-risk patients. High radiation dose is an important predictor of local control of intermediate-risk prostate cancer. Low-tier intermediate-risk patients have adequate tumor control with BT alone. High-tier intermediate-risk patients have non inferior outcomes with BT followed by EBRT. Patients with a Gleason score of 4+3 may warrant more aggressive combination therapy. Author Disclosure: A. Yorozu: None. S. Sutani: None. R. Kota: None. S. Saito: None. K. Toya: None.
Conclusion: In a selected population of patients, our results suggest that erectile dysfunction after bracytherapy could be strongly correlated with the doses to the PA. A specific optimization of the seeds implantation based on the dose to these PA could increase the rate of erectile preservation. Author Disclosure: Z. Youbi: None. C. Udrescu: None. S. Horn: None. J. Ribouton: None. F. Lorchel: None. O. Rouviere: None. O. Chapet: None.
2663 Irradiation of the Pudendal Arteries Induces Erectile Dysfunction in Patients Treated by Brachytherapy for Prostate Cancer Z. Youbi,1 C. Udrescu,1 S. Horn,1 J. Ribouton,1 F. Lorchel,1 O. Rouviere,2 and O. Chapet1; 1Centre Hospitalier Lyon Sud, Pierre Benite, France, 2 Hopital Edouard Herriot, Lyon, France Purpose/Objective(s): Erectile dysfunction (ED) is a common side effect in men treated with Iodine-125 brachytherapy (BT) for a prostate cancer. Several studies suggested that ED could be correlated to the doses of irradiation delivered to the pudendal arteries (PA). However these studies were mainly performed in patients treated with external beam irradiation. The purpose of the present study was to determine the relationship between the doses to the PA and the ED after BT. Materials/Methods: Twenty patients (age 65 years; initial IIEF 5 score 20) were selected according to their IIEF-5 score at 3-year after a prostate BT at 145Gy. Ten patients had no ED (Group A; average IIEF5Z22 (20-25)) and 10 had ED (Group B; average IIEF5Z13.2 (11-16)). All of them had a dosimetric CT scan control performed 4 weeks after the implantation using automatic seed detection. Quality of implantation was measured using the conformity index (100% of the dose) and the coverage index. The prostate and the PA were delineated on each slice. Dosimetric parameters for the PA (D5%, D50%) and distance between the apex of the prostate and the right and left PA) were analyzed and compared between the two groups. Results: The average age of the patients was 61.6 years (59-65) and 59.3 years (42-64) in groups A and B respectively. The mean prostate volumes were similar (44cc vs. 42cc). In the 20 patients, the mean conformity index was 0.7 (0.64-0.78) and the mean coverage index was 0.97 (0.93-0.99). The two indexes were equivalent between the two groups. Dosimetric PA parameters and distances from the prostate’s apex to the PA are available in Table 1. A significant difference between the two groups of patients with and without ED is noted for all the evaluated parameters. Abstract 2663; Table 1 Doses (Gy) to pudendal arteries and distances (cm) between the prostate’s apex and the PA for the two groups Without ED
With ED
p
D5% (Gy) D50% (Gy) Distance apex-RPA (cm)
20.7 (13.9-25.2) 10.4 (7.7-20.9) 1.7 (1.2-3.4)
33.1 (30.8-37.2) 16.8 (14.1-18.3) 1.1 (0.6-2.4)
< 0.0001 Z 0.0089 < 0.0011
D5% (Gy) D50% (Gy) Distance apex-LPA (cm)
18.4 (15.2-23.1) 11.6 (7.8-18.2) 1.8 (1-2.8)
33.8 (29.1-37.6) 15.2 (12.8-17.1) 1.2 (0.8-2.2)
< 0.0001 Z 0.0753 Z 0.0052
RPA
LPA
RPA Z right pudendal artery; LPA Z left pudendal artery; ED Z erectile dysfunction.
2664 Testosterone Levels and Sexual Quality of Life Following Stereotactic Body Radiation Therapy for Prostate Cancer: A Multi-institutional Analysis of Prospective Trials Y. Yuan,1 D.B. Fuller,2 G. Mardirossian,2 M.L. Steinberg,1 C.R. King,3 and A.U. Kishan3; 1University of California, Los Angeles, Los Angeles, CA, 2Genesis Healthcare Partners, San Diego, CA, 3Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA Purpose/Objective(s): Stereotactic body radiotherapy (SBRT) is being increasingly utilized for the definitive treatment of low to intermediate risk prostate cancer. Sources of higher incidental testicular dose arises from the use of non-coplanar beams, larger scatter dose fractions, and increased frequency of image-guidance. There remains little knowledge of how testicular scatter dose during SBRT affects testicular function and sexual quality of life after treatment. Materials/Methods: Patients with low to intermediate risk prostate cancer who were enrolled in two multi-institutional prospective clinical trials evaluating prostate SBRT between 2009 and 2014 were identified. Pre- and post-treatment testosterone (T) values were available. Patient-reported quality of life measures were obtained via Expanded Prostate Composite Index-26 (EPIC) questionnaires. The median absolute and relative changes in T within 6 months, 12 months, and 24 months after completion of SBRT were compared to the median pre-treatment baseline using the WilcoxonMann-Whitney test. Average pre- and post-treatment EPIC scores were compared using unpaired t-tests. Results: A total of 77 patients were analyzed with up to 24 months of follow up. The median age was 70 with a median baseline pre-treatment T of 386 ng/dL. Within 6 months of completion of SBRT, the median T was 332 ng/dL, which corresponded to a statistically significant median decrease of 26 ng/dL (p < 0.01) and a median relative decrease of 7.6% (p < 0.01). At 12 months after SBRT, the median T was 345 ng/dL, which correlated with a statistically significant median decrease of 60 ng/dL (p < 0.01) and a median relative decrease of 15.3% (p < 0.01). By 2 years, the median T was 370 ng/dL, corresponding to a non-significant median decrease of 19.5 ng/dL (p Z 0.30) and a median relative decrease of 5.3% (p Z 0.30). The median EPIC sexual function scores pretreatment and within 6, 12, and 24 months after treatment were 63, 43 (p Z 0.98), 47 (p Z 0.98), and 63 (p Z 0.36). The median EPIC hormone/vitality scores pretreatment and within 6, 12, and 24 months after treatment were 100, 95 (p Z 0.21), 100 (p Z 0.97), and 100 (p Z 0.18). Conclusion: In this multi-institutional retrospective study of patients with low to intermediate risk prostate cancer who received prostate SBRT, we found a statistically significant decline in median T levels at 6 and 12 months after treatment although this change never reached any clinically significant hypogonadal state. By 24 months the median T levels were no longer significantly different from baseline. Despite the transient decline in median T levels there was no corresponding significant change in sexual function or hormone/vitality scores. Longer follow up is needed to confirm that low dose testicular scatter does not lead to any lasting or clinically consequential declines in T levels after prostate SBRT. Author Disclosure: Y. Yuan: None. D.B. Fuller: Stock; Accuray, Varian. G. Mardirossian: None. M.L. Steinberg: Honoraria; Accuray. C.R. King: None. A.U. Kishan: None.
2661 Androgen Deprivation Therapy and Elevated Risk of Rheumatoid Arthritis in Patients With Prostate Cancer D.D. Yang,1 A. Krasnova,2 K.T. Nead,3 Q.D. Trinh,4 and P.L. Nguyen5; 1 Harvard Medical School, Boston, MA, 2Center for Surgery and Public Health, Brigham and Women’s Hospital, Boston, MA, 3Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, 4 Center for Surgery and Public Health and Division of Urological Surgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, 5 Department of Radiation Oncology, Dana-Farber Cancer Institute and Brigham and Women’s Hospital, Harvard Medical School, Boston, MA Purpose/Objective(s): Testosterone is immunosuppressive, and studies have shown that men with untreated hypogonadism are at increased risk for autoimmune conditions. To date, there has been no evidence linking androgen deprivation therapy (ADT) to the development of autoimmune
Poster Viewing E277 diseases, including rheumatoid arthritis (RA). We investigated the association between ADT and RA. Materials/Methods: We identified 138,770 men age 66 years or older with stage I-III prostate cancer using the Surveillance, Epidemiology, and End Results -Medicare linked database from 1992 through 2009, excluding patients with a diagnosis of RA in the prior year. Chi-squared test was utilized to compare differences in Kaplan-Meier event rates. Cox regression using inverse probability of treatment weighting to adjust for demographic and clinical factors was used to examine the association between pharmacologic ADT and diagnosis of RA. Results: The 39.9% of patients (55,321) who received ADT experienced a higher 5-year rate of RA than patients who did not receive ADT (4.3% vs. 3.4%, p<0.001), with a number needed to harm of 110 patients. Receipt of any ADT was associated with a 23% increased risk of developing RA (hazard ratio [HR] 1.23, 95% CI 1.12-1.35, p<0.001). The risk of RA increased with a longer duration of ADT, from 17% with 1-6 months (HR 1.17, 95% CI 1.09-1.26, p<0.001) and 26% with 7-11 months (HR 1.26, 95% CI 1.09-1.45, pZ0.002) to 36% with 12 months (HR 1.36, 95% CI 1.16-1.60, p<0.001). Conclusion: ADT was associated with an elevated risk of developing RA in this large cohort of elderly men with non-metastatic prostate cancer. The risk was higher with a longer duration of ADT. Our findings are the first linking ADT to an increased risk of autoimmunity and add to mounting evidence of the many adverse effects of ADT that should prompt physicians to thoughtfully weigh its risks and benefits, particularly for intermediate-risk patients. Author Disclosure: D.D. Yang: None. A. Krasnova: None. K.T. Nead: None. Q. Trinh: None. P.L. Nguyen: Consultant; GI Windows, Infinity Pharmaceuticals, Nanobiotix. Advisory Board; Dendreon, Ferring, Genome DX, Medivation. ; Genitourinary Cancers Symposium.
2662 Factors Predicting Outcome for Intermediate-Risk Prostate Cancer Patients Undergoing I-125 Brachytherapy With or Without External Beam Radiation Therapy A. Yorozu, S. Sutani, R. Kota, S. Saito, and K. Toya; Tokyo Medical Center, Tokyo, Japan Purpose/Objective(s): To evaluate the influence of patient- and treatment-related factors on clinical outcomes in intermediate-risk prostate cancer patients undergoing I-125 brachytherapy (BT). Materials/Methods: From a prospectively collected database of 1846 men treated for prostate cancer with I-125 brachytherapy between 2003 and 2012, 1000 men with intermediate-risk features were analyzed. A total of 402 men were treated only with BT, and another 598 were treated with BT combined with external beam radiotherapy (EBRT). Low-tier intermediate-risk patients (defined as a clinical stage of T1-2, PSA level of <10 ng/ mL, and a Gleason score of 3+4 with a biopsy positive core rate of <33.4%) received BT alone. The prescription dose was 145 Gy without EBRT or 110 Gy with EBRT, and the dose to 90% of the prostate (D90) was 110e130% of the prescription dose. In combined EBRT, 45 Gy in 25 fractions was given to the prostate and seminal vesicles. Neoadjuvant androgen deprivation (NAD) was given to 414 men. Patient and treatment factors were examined for an association with clinical outcomes. Biochemical failure was determined by the Phoenix definition. Among patients with biochemical failure, local recurrence was defined as the detection of cancer by post-treatment biopsy analysis, by MRI or by digital rectal exam. Prostate-cancer-specific mortality (PCSM) and overall survival (OS) were assessed. Radiation doses were converted to the biological effective dose (BED) using an a/b ratio of 2 and the D90 values of the prostate from a day-30 CT scan. The Kaplan-Meier method and Cox regression model were used for analysis. Results: At a median follow-up of 8 years, freedom from biochemical failure (FFbF), actuarial local recurrence rate, PCSM, and OS were 91.9%, 1.3%, 1.1%, 91.5%, respectively. In univariate and multivariate analyses, a Gleason score of 4+3 was the only significant predictor of FFbF
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(pZ0.001), PCSM (p<0.01), and OS (p<0.05). None of the other variables (PSA, T-factor, positive core rate, multiple intermediate-risk factors, EBRT, NAD, or BED) was found to be statistically significant predictor of these outcomes. BED (<200 Gy2) and BT alone were significant predictors for local recurrence in univariate analysis, and BED was significant (p<0.05) in multivariate analysis. Overall, NAD did not predict FFbF (pZ0.075). In patients with a Gleason score of 4+3, FFbF was 92.9% with NAD and 84.1% without NAD (p<0.05). Conclusion: A Gleason score of 4+3 is an important predictor of FFbF, PCSM, and OS in intermediate-risk patients. High radiation dose is an important predictor of local control of intermediate-risk prostate cancer. Low-tier intermediate-risk patients have adequate tumor control with BT alone. High-tier intermediate-risk patients have non inferior outcomes with BT followed by EBRT. Patients with a Gleason score of 4+3 may warrant more aggressive combination therapy. Author Disclosure: A. Yorozu: None. S. Sutani: None. R. Kota: None. S. Saito: None. K. Toya: None.
Conclusion: In a selected population of patients, our results suggest that erectile dysfunction after bracytherapy could be strongly correlated with the doses to the PA. A specific optimization of the seeds implantation based on the dose to these PA could increase the rate of erectile preservation. Author Disclosure: Z. Youbi: None. C. Udrescu: None. S. Horn: None. J. Ribouton: None. F. Lorchel: None. O. Rouviere: None. O. Chapet: None.
2663 Irradiation of the Pudendal Arteries Induces Erectile Dysfunction in Patients Treated by Brachytherapy for Prostate Cancer Z. Youbi,1 C. Udrescu,1 S. Horn,1 J. Ribouton,1 F. Lorchel,1 O. Rouviere,2 and O. Chapet1; 1Centre Hospitalier Lyon Sud, Pierre Benite, France, 2 Hopital Edouard Herriot, Lyon, France Purpose/Objective(s): Erectile dysfunction (ED) is a common side effect in men treated with Iodine-125 brachytherapy (BT) for a prostate cancer. Several studies suggested that ED could be correlated to the doses of irradiation delivered to the pudendal arteries (PA). However these studies were mainly performed in patients treated with external beam irradiation. The purpose of the present study was to determine the relationship between the doses to the PA and the ED after BT. Materials/Methods: Twenty patients (age 65 years; initial IIEF 5 score 20) were selected according to their IIEF-5 score at 3-year after a prostate BT at 145Gy. Ten patients had no ED (Group A; average IIEF5Z22 (20-25)) and 10 had ED (Group B; average IIEF5Z13.2 (11-16)). All of them had a dosimetric CT scan control performed 4 weeks after the implantation using automatic seed detection. Quality of implantation was measured using the conformity index (100% of the dose) and the coverage index. The prostate and the PA were delineated on each slice. Dosimetric parameters for the PA (D5%, D50%) and distance between the apex of the prostate and the right and left PA) were analyzed and compared between the two groups. Results: The average age of the patients was 61.6 years (59-65) and 59.3 years (42-64) in groups A and B respectively. The mean prostate volumes were similar (44cc vs. 42cc). In the 20 patients, the mean conformity index was 0.7 (0.64-0.78) and the mean coverage index was 0.97 (0.93-0.99). The two indexes were equivalent between the two groups. Dosimetric PA parameters and distances from the prostate’s apex to the PA are available in Table 1. A significant difference between the two groups of patients with and without ED is noted for all the evaluated parameters. Abstract 2663; Table 1 Doses (Gy) to pudendal arteries and distances (cm) between the prostate’s apex and the PA for the two groups Without ED
With ED
p
D5% (Gy) D50% (Gy) Distance apex-RPA (cm)
20.7 (13.9-25.2) 10.4 (7.7-20.9) 1.7 (1.2-3.4)
33.1 (30.8-37.2) 16.8 (14.1-18.3) 1.1 (0.6-2.4)
< 0.0001 Z 0.0089 < 0.0011
D5% (Gy) D50% (Gy) Distance apex-LPA (cm)
18.4 (15.2-23.1) 11.6 (7.8-18.2) 1.8 (1-2.8)
33.8 (29.1-37.6) 15.2 (12.8-17.1) 1.2 (0.8-2.2)
< 0.0001 Z 0.0753 Z 0.0052
RPA
LPA
RPA Z right pudendal artery; LPA Z left pudendal artery; ED Z erectile dysfunction.
2664 Testosterone Levels and Sexual Quality of Life Following Stereotactic Body Radiation Therapy for Prostate Cancer: A Multi-institutional Analysis of Prospective Trials Y. Yuan,1 D.B. Fuller,2 G. Mardirossian,2 M.L. Steinberg,1 C.R. King,3 and A.U. Kishan3; 1University of California, Los Angeles, Los Angeles, CA, 2Genesis Healthcare Partners, San Diego, CA, 3Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA Purpose/Objective(s): Stereotactic body radiotherapy (SBRT) is being increasingly utilized for the definitive treatment of low to intermediate risk prostate cancer. Sources of higher incidental testicular dose arises from the use of non-coplanar beams, larger scatter dose fractions, and increased frequency of image-guidance. There remains little knowledge of how testicular scatter dose during SBRT affects testicular function and sexual quality of life after treatment. Materials/Methods: Patients with low to intermediate risk prostate cancer who were enrolled in two multi-institutional prospective clinical trials evaluating prostate SBRT between 2009 and 2014 were identified. Pre- and post-treatment testosterone (T) values were available. Patient-reported quality of life measures were obtained via Expanded Prostate Composite Index-26 (EPIC) questionnaires. The median absolute and relative changes in T within 6 months, 12 months, and 24 months after completion of SBRT were compared to the median pre-treatment baseline using the WilcoxonMann-Whitney test. Average pre- and post-treatment EPIC scores were compared using unpaired t-tests. Results: A total of 77 patients were analyzed with up to 24 months of follow up. The median age was 70 with a median baseline pre-treatment T of 386 ng/dL. Within 6 months of completion of SBRT, the median T was 332 ng/dL, which corresponded to a statistically significant median decrease of 26 ng/dL (p < 0.01) and a median relative decrease of 7.6% (p < 0.01). At 12 months after SBRT, the median T was 345 ng/dL, which correlated with a statistically significant median decrease of 60 ng/dL (p < 0.01) and a median relative decrease of 15.3% (p < 0.01). By 2 years, the median T was 370 ng/dL, corresponding to a non-significant median decrease of 19.5 ng/dL (p Z 0.30) and a median relative decrease of 5.3% (p Z 0.30). The median EPIC sexual function scores pretreatment and within 6, 12, and 24 months after treatment were 63, 43 (p Z 0.98), 47 (p Z 0.98), and 63 (p Z 0.36). The median EPIC hormone/vitality scores pretreatment and within 6, 12, and 24 months after treatment were 100, 95 (p Z 0.21), 100 (p Z 0.97), and 100 (p Z 0.18). Conclusion: In this multi-institutional retrospective study of patients with low to intermediate risk prostate cancer who received prostate SBRT, we found a statistically significant decline in median T levels at 6 and 12 months after treatment although this change never reached any clinically significant hypogonadal state. By 24 months the median T levels were no longer significantly different from baseline. Despite the transient decline in median T levels there was no corresponding significant change in sexual function or hormone/vitality scores. Longer follow up is needed to confirm that low dose testicular scatter does not lead to any lasting or clinically consequential declines in T levels after prostate SBRT. Author Disclosure: Y. Yuan: None. D.B. Fuller: Stock; Accuray, Varian. G. Mardirossian: None. M.L. Steinberg: Honoraria; Accuray. C.R. King: None. A.U. Kishan: None.