103 Patterns of Lymph Node Positivity on 11 C-acetate PET Imaging in Correlation to the RTOG Pelvic Radiation Field for Prostate Cancer C.M. McClinton, M. Niroumand, J. Hill, R. Dusing, P. Kumar, and X. Shen; University of Kansas Medical Center, Kansas City, KS Purpose/Objective(s): 11 C-acetate positron emission tomography (PET) imaging allows for the detection of occult metastatic disease that may otherwise go undetected with standard imaging for prostate cancer. The aim of this study was to evaluate the ability of the standard Radiation Therapy Oncology Group (RTOG) pelvic radiation field to cover all sites of lymph node disease in patients with node-positive prostate cancer as determined by 11 C-acetate PET imaging. Materials/Methods: A retrospective analysis was conducted on 125 male patients with prostate cancer who underwent 11 C-acetate PET scans at our institution between 2007 and 2014. Patients with non-lymph node metastatic disease and/or those who were negative for nodal disease on PET imaging, as determined by the interpreting radiologist, were excluded from this study. On the node-positive scans, individual lymph nodes were characterized by location, size on corresponding computed tomography-based attenuation correction (CTAC) imaging, and standardized uptake value (SUV) on 11 C-acetate PET. Anatomic location of each positive node was then transposed to the standard RTOG pelvic radiation field. Results: A total of 176 11 C-acetate PET scans (range: 1e5 scans) on 125 men were reviewed. The majority of patients were white (123, 98%) with a mean age of 66 years. Of the 176 scans, 55 scans (from 53 men) met criteria for inclusion in the study. Thirty-six patients had a prior prostatectomy (68%), 9 had brachytherapy (16%), and 8 had external beam radiotherapy (15%). Median prostate-specific antigen at diagnosis was 8.23 (1.41e85). Gleason score (GS) was available for 45 patients: 11 were GS 6 or less (24%), 19 were GS 7 (42%), 7 were GS 8 (16%), and 8 were GS 9e10 (18%). The 55 included scans contained a total of 161 positive lymph nodes. Of the positive individual nodes, 76.5% were less than 1 cm. The most frequent sites of lymph node involvement were in the distribution of the external iliacs (33.5%), common iliacs (16.8%), and para-aortics (18.0%). Additionally, 11.2% of positive nodes were identified as nodes of Cloquet. In relation to the RTOG pelvic radiation field, 48.4% of positive nodes were within the treatment field while 51.6% fell outside the field. Of the nodes that were outside of the radiation field, 34.9% were para-aortic, 22.9% were proximal common iliac, 15.7% were distal external iliac, and 21.7% were nodes of Cloquet. Conclusion: Based on 11 C-acetate PET imaging, the RTOG pelvic radia- tion field will miss nearly half of all positive lymph nodes. Clinicians should use caution when using the standard RTOG contouring atlas in patients with node-positive prostate cancer. 11 C-acetate PET imaging may be useful in defining target volumes for patients with node-positive pros- tate cancer. Author Disclosure: C.M. McClinton: None. M. Niroumand: None. J. Hill: None. R. Dusing: None. P. Kumar: None. X. Shen: None. 104 Seven-Year Outcomes of a Prospective Trial of Concomitant Docetaxel and Proton Therapy for High-Risk Prostate Cancer N.P. Mendenhall, 1 C.M. Bryant, 1 B.S. Hoppe, 1 R.C. Nichols, Jr, 1 W.M. Mendenhall, 2 C.G. Morris, 1 Z. Li, 3 C.R. Williams, 3 J.A. Costa, 3 and R.H. Henderson 1 ; 1 University of Florida Health Proton Therapy Institute, Jacksonville, FL, 2 University of Florida, Gainesville, FL, 3 University of Florida, Jacksonville, FL Purpose/Objective(s): To assess late outcomes of a novel approach to treatment of high-risk prostate cancer using concomitant docetaxel and proton therapy (PT). Materials/Methods: Forty men with high-risk prostate cancer (PCa) were enrolled on a prospective institutional review board-approved trial of 78 Gy (RBE) in 39 fractions to the prostate and seminal vesicles (without pelvic node irradiation) plus docetaxel followed by 6 months of androgen deprivation therapy (ADT). The primary objective was to measure grade 3+ toxicity; secondary objectives were to document disease control and patient-reported quality-of-life assessment. Median age was 72 years (range, 53e88 years). Eligibility required prostate-specific antigen (PSA) of 20 and/or Gleason score of 8 and/or clinical stage of T3. During proton therapy docetaxel was delivered in weekly doses of 20 mg/m2. Median follow-up is 7.2 years (range, 0.5 to 8.3 years). International Prostate Symptom Score (IPSS), CTCAE version 3.0 toxicity, and Expanded Prostate Index Composite (EPIC) were performed at baseline and 6-month intervals after treatment. Results: Patient status is as follows: alive without evidence of disease, 26 patients; alive with PCa, 5; dead of PCa, 4; dead of intercurrent disease, 5, including 1 with PSA progression; lost to follow-up, 2, who were alive and without disease at 3.7 and 4.6 years after treatment. Freedom from biochemical and/or clinical disease progression and overall survival rates are 73% and 79% at 7 years. Patterns of progression include the following: PSA only (n Z 3) and PSA plus distant metastases (n Z 7, including 1 with pelvic node recurrence). Disease progression occurred in 2 of 24 patients with T1e2 and Gleason 8 disease and in 8 of 16 patients with either T3 or Gleason 9. Three CTCAE version 3 grade 3 genitourinary and 1 gastrointestinal events occurred, which resolved with intervention and did not recur. Respective baseline and last follow-up median patient-reported outcome scores in the 26 surviving patients who have remained free of disease pro- gression are as follows: EPIC bowel summary, 96 and 93; EPIC urinary incontinence, 100 and 90; EPIC urinary irritative and obstructive symptoms, 94 and 88; IPSS, 7 and 9; EPIC hormonal function, 90 and 90; and EPIC sexual function, 41 and 24. Conclusion: Proton therapy in conjunction with low-dose concomitant docetaxel was well tolerated and produced a disease control rate of 73% at 7 years of follow-up. Ninety-two percent of patients with T1e2 disease and Gleason 8 remain disease free, but more intensive therapy appears warranted for those with either T3 or Gleason 9 disease. While well tolerated, the contribution of docetaxel in achieving disease control is unclear and will require future comparative studies. Author Disclosure: N.P. Mendenhall: None. C.M. Bryant: None. B.S. Hoppe: None. R. Nichols: None. W.M. Mendenhall: None. C.G. Morris: None. Z. Li: None. C.R. Williams: None. J.A. Costa: None. R.H. Henderson: None. 105 Integrative Radiotranscriptomic Analysis of Breast Carcinoma Identifies Androgen Receptor as a Target for Therapeutic Sensitization B. Yard, 1 E.K. Chie, 1 C. Peacock, 1 D. Adams, 2 P. Tamayo, 2 and M. Abazeed 1 ; 1 Cleveland Clinic, Cleveland, OH, 2 Broad Institute, Cambridge, MA Purpose/Objective(s): Comprehensive genomic profiling of breast cancer has demonstrated significant biologic diversity. Radiation therapy is a mainstay of treatment for breast cancer; however, current predictors of radiation response are largely limited to clinical and histopathological features and extensive systematic analyses of the correlation between radiotherapeutic sensitivity and -omic parameters remain insufficient. Materials/Methods: We developed new technology that makes possible the profiling of cancer cell line response to targeted and cytotoxic therapies in high-throughput capacity. We used this technology to study the radiosensitivity of 28 breast cancer cell lines annotated by the Cancer Cell Line Encyclopedia (CCLE) project. Gene Set Enrichment Analysis (GSEA) was performed to correlate radiosensitivity with gene expression features of the assayed cell lines. Results: We confirmed that the activity of ER and HER2, two previously characterized biomarkers of resistance to cytotoxic therapy, strongly predict for radiation resistance in breast cancer cells; in addition, one of the most correlated and intriguing gene sets identified were associated with the androgen receptor (AR) pathway. To validate the GSEA findings, we used CCLE data to show that HER2, ER, and AR mRNA levels were strongly Volume 93  Number 3S  Supplement 2015 Oral Scientific Sessions S47