- Email: [email protected]
Minimizing Immunosuppressive Effects of Photon and Proton Radiation Therapy on Circulating Lymphocytes
Volume 99 Number 2S Supplement 2017
Poster Viewing E577
were then adjusted for age, sex, and time from neoadjuvant treatment. The analysis was done using logistic regressions of response, with bootstrap standard errors for comparisons between treatment and no treatment. Results: Sixteen patients were included in the responders group. Thirteen patients, with a mean NAR score of 21.33, were included in the nonresponders group. The pretreatment median percent of PBLs positive for gH2AX in the responders group and non-responders group was 17.5% and 12.7% respectively (adjusted p Z 0.028). After 5 uM aphidicolin treatment, the median percent of PBLs positive for gH2AX for responders and non-responders was 25.9% and 19.9% respectively (adjusted p Z 0.039). After 2 Gy radiation treatment, the median percent of PBLs positive for gH2AX for responders and non-responders was 23% and 18.6% respectively (adjusted p Z 0.031). The median gH2AX difference between the two groups was not statistically better after 5 uM aphidicolin and 2 Gy radiation treatments when compared to pretreatment difference (p Z 0.99 and p Z 0.32 respectively). The rest of the DNA damaging treatments did not elicit a statistically significant difference in gH2AX on adjusted analysis between the responders and non-responders group. Conclusion: Higher baseline PBL gH2AX was correlated with a better response to CRT in locally advanced rectal cancer patients. Measuring PBL gH2AX after treatment with a number of DNA damaging agents did not better predict for the CRT response. Author Disclosure: V. Avkshtol: None. S. Arora: None. R.W. Lesh: None. E.A. Golemis: None. B. Egleston: None. J.E. Meyer: None.
immune markers including CD3 (T lymphocytes), F4/80 (macrophages) and PD-L1. All animal experiments were reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) of Columbia University Medical Center. Results: 100% of 47 mice developed tumors, with 0% surgical mortality. Tumor grafts grew more uniformly than tumors derived from intrarenal injection of 9464D cell suspension (P < 0.05). Tumors were clearly delineated within the kidney following injection of iohexol contrast agent, allowing precise radiation targeting. RT induced intratumoral PD-L1 expression. Combined SBRT/aPD1 was more effective than either SBRT or aPD1 alone in reducing the rate of tumor growth (P < 0.001) as well as tumor weight at 35 days post-implant (P < 0.05). Combination therapy, however, was associated with toxicity, with 40% of mice dying within one week following SBRT/aPD1 administration. Tumors treated with combined SBRT/aPD1 demonstrated dense infiltration by macrophages and T lymphocytes. Conclusion: Our intrarenal syngeneic tumor graft model of advanced-stage neuroblastoma produces uniform tumor growth and is amenable to imageguided radiation therapy. SBRT/ICI promotes tumor infiltration by immune cells and slows tumor growth, and further mechanistic studies are warranted. Author Disclosure: S. Barton: None. S. Okochi: None. C. Street: None. D. Banerjee: None. A. Kadenhe-Chiweshe: None. D.J. Yamashiro: None. E.P. Connolly: None.
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Combined Stereotactic Body Radiation Therapy and Immune Checkpoint Inhibition Slows Tumor Growth in a Novel Syngeneic Model of Neuroblastoma S.M. Barton,1 S. Okochi,2 C. Street,2 D. Banerjee,3 A. KadenheChiweshe,2 D.J. Yamashiro,3 and E.P. Connolly1; 1Department of Radiation Oncology, Columbia University Medical Center, New York, NY, 2 Department of Surgery, Columbia University Medical Center, New York, NY, 3Department of Pediatrics, Columbia University Medical Center, New York, NY
Minimizing Immunosuppressive Effects of Photon and Proton Radiation Therapy on Circulating Lymphocytes L. Basler,1 N. Andratschke,1 S. Ehrbar,1 G. Lucconi,2 A. Bolsi,2 A. Lomax,2 D.C. Weber,2 M. Guckenberger,1 and S. Tanadini-Lang1; 1 University Hospital Zuerich, Zuerich, Switzerland, 2Paul Scherrer Institute, Villigen, Switzerland
Purpose/Objective(s): The majority of pediatric patients diagnosed with advanced-stage neuroblastoma die from their disease despite intensive multimodality therapy. Combination stereotactic body radiation therapy (SBRT) and immune checkpoint inhibition (ICI) represents a promising therapeutic avenue. We sought to develop a highly reproducible, syngeneic mouse model of advanced-stage neuroblastoma, in order to investigate the effects of combination SBRT/ICI on local control and the tumor immune microenvironment. Materials/Methods: We prepared an intrarenal tumorgraft model using the 9464D cell line, derived from the TH-MYCN transgenic neuroblastoma mouse. Following tumor implantation, mice were randomized to SBRT versus sham RT, as well as concurrently dosed anti-PD-1 antibody (aPD1) versus isotype control. SBRT fractions were delivered using the Small Animal Radiation Research Platform in 360 degree axial arcs to minimize normal tissue toxicity. Given increased radioresistance of 9464D relative to human neuroblastoma cell lines, three 8-Gy fractions were delivered. Tumor volume was monitored via CT and 3D ultrasound. Quantitative multiplex immunohistochemistry (qmIHC) staining was performed for
Purpose/Objective(s): Tumor immune escape may be a major reason for failure of immunotherapy and has been shown to be potentially overcome by radiotherapy. However, radiation also has detrimental effects on tumor infiltrating and circulating lymphocytes (CLs). This in silico planning study aimed to model the low-dose effects of photon- and proton-irradiation on CLs depending on dose, fractionation and treatment technique in the context of cancer immunotherapy. Materials/Methods: A model has been implemented in MATLAB to estimate the dose delivered to CLs during stereotactic body radiotherapy of a liver metastasis treated with 3 x 15 Gy. Three scenarios were evaluated, with a virtual liver metastasis positioned at different intra-hepatic locations. Six photon and two proton treatment plans were generated for each location: Volumetric modulated arc therapy (VMAT) and 3D conformal radiotherapy (3DCRT) with and without flattening filter, and proton radiotherapy with either single field uniform dose (SFUD) or intensity modulated proton therapy (IMPT) techniques using a pencil beam scanning delivery paradigm. Cumulative dose to CLs was calculated using a DVH based convolution algorithm. It considers the hepatic blood flow and velocity, hepatic transition time, total body blood volume, heart-to-heart circulation time, treatment delivery time, dose rate and beam energy. A dose of 0.5Gy was considered effective in inactivating or killing CLs.
Abstract 3374 Treatment modality
Beam energy
Flattening filter
3DCRT 3DCRT 3DCRT VMAT VMAT VMAT Proton IMPT Proton SFUD
10 MV 6 MV 6 MV 10 MV 6 MV 6 MV
FFF FFF FF FFF FFF FF
Dose rate 2400 MU/min 1400 MU/min 600 MU/min 2400 MU/min 1400 MU/min 600 MU/min
Number of fields/arcs
Total BOT
MLD
CL0.5
7 7 7 2 3 4 2 2
57 s 111 s 253 s 74 s 147 s 363 s 78 s 71 s
4.3 4.3 4.3 3.8 3.7 3.7 2.7 2.4
15,2% 22,9% 29,9% 18,5% 23,0% 24,1% 11,8% 9,8%
Gy Gy Gy Gy Gy Gy Gy Gy
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Results: Mean liver dose (MLD) was mostly influenced by treatment modality: lowest values were achieved with protons followed by VMAT and 3DCRT. In contrast, the proportion of CLs receiving 0.5Gy (CL0.5) was mostly influenced by beam-on time (BOT), which is associated with photon energy and dose rate. 7-field 3D-CRT with 10MV FFF followed by VMAT with 10MV FFF resulted in lowest mean CL0.5 values of 15.2% and 18.5% (Table). 2-field proton plans further reduced CL0.5 to 9.8% for the SFUD and 11.8% for the IMPT plan. Additionally, metastasis location influenced CL0.5, with a mean of 16.2% (8.8 - 23.5%) for the apical, 15.8% (7.9 25.9%) for the basal and 26.2% (12.8 - 40.2%) for the central location. Conclusion: A model has been established to estimate immunosuppressive effects of radiotherapy through inactivation of circulating lymphocytes. In contrast to our initial assumption that integral dose might be the most important factor influencing the proportion of lymphocytes receiving >0.5 Gy, treatment delivery time had the strongest impact: best CL-sparing was achieved with 10MV FFF VMAT and 3D photon techniques with proton radiotherapy further improving lymphocyte sparing. Author Disclosure: L. Basler: None. N. Andratschke: None. S. Ehrbar: None. G. Lucconi: None. A. Bolsi: None. A. Lomax: None. D.C. Weber: None. M. Guckenberger: None. S. Tanadini-Lang: None.
Author Disclosure: C. Bergom: None. B. Fish: None. T. Gasperetti: None. R.A. Schlaak: None. A. Frei: None. M. Medhora: Advisor; Positive Bioscience, Mumbai, India.
3375 Identifying Genetic Variants that Enhance the Therapeutic Ratio of Radiation C. Bergom, B. Fish, T. Gasperetti, R.A. Schlaak, A. Frei, and M. Medhora; Medical College of Wisconsin, Milwaukee, WI Purpose/Objective(s): Radiation therapy (RT) is used by more than 60% of cancer patients, but RT is typically not personalized based upon tumor sensitivity or normal tissue sensitivity biomarkers. RT doses are often constrained so the risk of severe damage to adjacent normal tissues (e.g. heart, lungs, kidneys) is <5-10%, meaning that in over 90% of patients it may be possible to dose escalate RT to the tumor without unacceptable side effects if predictive biomarkers for normal tissue toxicity were available. Our goal is to identify genetic factors that will allow more personalized and effective RT or drug targets for mitigation or protection of normal tissue injuries. Materials/Methods: To demonstrate the impact of host genetic differences on normal tissue RT toxicity, we utilized consomic rat models. Chromosome 3 from the Brown Norway (BN) rat strain was introgressed by repeated back crossing into a SS-Dahl (SS) background to derive the strain SS.BN3. Host factors in the SS.BN3 strain have been shown to alter the RT sensitivity of breast tumors when compared to the SS strain. Congenic rats with only a small (36 megabase, Mb) region of chromosome 3 from SS rats were used to genetically map the phenotypes. Eight-week-old female rats were treated with 13 Gy whole thorax RT or 12.5 Gy total body RT with bone marrow rescue, and animals were examined for radiation pneumonitis and nephropathy. Blood urea nitrogen (BUN) levels were obtained in the total body RT group. Survival curves were analyzed using Kaplan Meier method and log-rank test. Results: The SS.BN3 consomic rats demonstrated protection against lung and kidney RT toxicity compared to SS rats. In rats receiving total body RT, there was a significant and dramatic improvement in survival, with all SS rats (nZ9) morbid due to renal damage by day 140, while no SS.BN3 rats were morbid (p<0.01). At 120 days post RT, the median BUN level in SS rats was >120 mg/ dl versus within normal limits for the SS.BN3 rats. In rats administered whole thorax RT, more SS rats were morbid due to lung toxicity 50-80 days after RT, while SS.BN3 rats demonstrated little lung toxicity. Preliminary results suggest the radioprotective phenotype maps to a w36 Mb region containing genes important for vasculogenesis. The SS.BN3 rats had previously been demonstrated to have abnormal blood vessels and conferred enhanced RT tumor radiosensitivity due to tumor microenvironmental factors. Conclusion: Taken together, the consomic rat models present a novel system to genetically map variants that protect against normal tissue RT toxicity and enhance tumor RT responses. Our data suggest genetic variant(s) on rat chromosome 3 both protect normal tissues and enhance tumor responses to improve the therapeutic ratio for RT. Future work will identify these genes for therapeutic targeting and better prediction of RT responses.
3376 Comprehensive mRNA Prognostic Biomarker Analysis of Grade 2/3 Gliomas S. Beyer,1 E.H. Bell,1 J. McElroy,2 O. Oehlke,3 J. Fleming,1 A. Becker,1 O. Staszewski,3 M. Prinz,3 A. Grosu,4 and A. Chakravarti1; 1The Ohio State University, Columbus, OH, 2The Ohio State University, Center for Biostatistics, Columbus, OH, 3University of Freiburg, Freiburg, Germany, 4 Department of Radiation Oncology, University Medical Center Freiburg, Freiburg, Germany Purpose/Objective(s): Grade II and III gliomas exhibit variable prognoses and responses to chemotherapy and radiation. Gliomas have traditionally been categorized according to grade and histology, however predicting prognosis and treatment response with this classification system is challenging. The World Health Organization released a new classification system for gliomas based on histology and molecular biomarkers, including isocitrate dehydrogenase (IDH) mutations and 1p/19q co-deletions, thus improving our ability to predict tumor prognosis. Previous studies have revealed prognostic molecular subgroups, including IDH wild-type, IDH mutant/1p/19q intact and IDH mutant/1p/19q co-deleted. Our study aims to identify prognostic biomarkers of Grade II/III gliomas that are independent of IDH and 1p/19 status by mRNA profiling. Materials/Methods: We established a clinical database of 58 Grade II (nZ19) and III (nZ38) gliomas from Freiburg, Germany, with corresponding tissue. We extracted RNA from formalin-fixed paraffin embedded (FFPE) Grade II/III glioma tissues and utilized the Affymetrix HTA ClariomD array. Normalization (RMA) and summarization were carried out using Affymetrix transcriptome analysis console software. Cox regression analysis identified mRNA expression significantly associated with overall survival (OS). Over-represented signaling pathways were identified by Ingenuity Pathway Analysis. Results: Our analysis identified 6,998 probe sets significantly associated with OS (p<0.05) independent of IDH mutation status, 1p/19q co-deletion status and age. 4,643 probe sets corresponded to protein-coding genes (2,443 with high hazard ratio (HR) and 2,200 with low HR). Conclusion: Axon guidance signaling and invasion/cell migration pathways were over-represented among genes associated with decreased OS (high HR) independent of IDH and 1p/19q status. Pathways involving lymphocyte/chemokine signaling were over-represented among genes associated with increased OS (low HR). An analysis of predictive biomarkers is currently ongoing to identify gene expression associated with treatment response among gliomas (surgery alone, adjuvant RT, or adjuvant chemotherapy) and will be presented at the annual ASTRO meeting. Future studies will include a larger institutional cohort of gliomas for validation of these prognostic and predictive biomarkers in addition to functional characterization of biomarkers in vitro. Author Disclosure: S. Beyer: Employee; The Ohio State University. E.H. Bell: None. J. McElroy: Employee; The Ohio State University. O. Oehlke: None. J. Fleming: None. A. Becker: None. O. Staszewski: None. M. Prinz: None. A. Grosu: None. A. Chakravarti: None.
3377 Targeted Inhibition of PI3K and MEK in Combination With Radiation Therapy in UT15: A Murine Model of Head and Neck Squamous Cell Carcinoma K.G. Blas Jr,1 S. Galoforo,2 T.G. Wilson,2 S.A. Krueger,3 I.S. Grills,4 B. Marples,5 and G.D. Wilson4; 1Beaumont Health, Royal Oak, MI, 2 Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI, 3MI Bioresearch, Ann Arbor, MI, 4Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, 5University of Miami Miller School of Medicine, Department of Radiation Oncology, Miami, FL
Poster Viewing E577
were then adjusted for age, sex, and time from neoadjuvant treatment. The analysis was done using logistic regressions of response, with bootstrap standard errors for comparisons between treatment and no treatment. Results: Sixteen patients were included in the responders group. Thirteen patients, with a mean NAR score of 21.33, were included in the nonresponders group. The pretreatment median percent of PBLs positive for gH2AX in the responders group and non-responders group was 17.5% and 12.7% respectively (adjusted p Z 0.028). After 5 uM aphidicolin treatment, the median percent of PBLs positive for gH2AX for responders and non-responders was 25.9% and 19.9% respectively (adjusted p Z 0.039). After 2 Gy radiation treatment, the median percent of PBLs positive for gH2AX for responders and non-responders was 23% and 18.6% respectively (adjusted p Z 0.031). The median gH2AX difference between the two groups was not statistically better after 5 uM aphidicolin and 2 Gy radiation treatments when compared to pretreatment difference (p Z 0.99 and p Z 0.32 respectively). The rest of the DNA damaging treatments did not elicit a statistically significant difference in gH2AX on adjusted analysis between the responders and non-responders group. Conclusion: Higher baseline PBL gH2AX was correlated with a better response to CRT in locally advanced rectal cancer patients. Measuring PBL gH2AX after treatment with a number of DNA damaging agents did not better predict for the CRT response. Author Disclosure: V. Avkshtol: None. S. Arora: None. R.W. Lesh: None. E.A. Golemis: None. B. Egleston: None. J.E. Meyer: None.
immune markers including CD3 (T lymphocytes), F4/80 (macrophages) and PD-L1. All animal experiments were reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) of Columbia University Medical Center. Results: 100% of 47 mice developed tumors, with 0% surgical mortality. Tumor grafts grew more uniformly than tumors derived from intrarenal injection of 9464D cell suspension (P < 0.05). Tumors were clearly delineated within the kidney following injection of iohexol contrast agent, allowing precise radiation targeting. RT induced intratumoral PD-L1 expression. Combined SBRT/aPD1 was more effective than either SBRT or aPD1 alone in reducing the rate of tumor growth (P < 0.001) as well as tumor weight at 35 days post-implant (P < 0.05). Combination therapy, however, was associated with toxicity, with 40% of mice dying within one week following SBRT/aPD1 administration. Tumors treated with combined SBRT/aPD1 demonstrated dense infiltration by macrophages and T lymphocytes. Conclusion: Our intrarenal syngeneic tumor graft model of advanced-stage neuroblastoma produces uniform tumor growth and is amenable to imageguided radiation therapy. SBRT/ICI promotes tumor infiltration by immune cells and slows tumor growth, and further mechanistic studies are warranted. Author Disclosure: S. Barton: None. S. Okochi: None. C. Street: None. D. Banerjee: None. A. Kadenhe-Chiweshe: None. D.J. Yamashiro: None. E.P. Connolly: None.
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Combined Stereotactic Body Radiation Therapy and Immune Checkpoint Inhibition Slows Tumor Growth in a Novel Syngeneic Model of Neuroblastoma S.M. Barton,1 S. Okochi,2 C. Street,2 D. Banerjee,3 A. KadenheChiweshe,2 D.J. Yamashiro,3 and E.P. Connolly1; 1Department of Radiation Oncology, Columbia University Medical Center, New York, NY, 2 Department of Surgery, Columbia University Medical Center, New York, NY, 3Department of Pediatrics, Columbia University Medical Center, New York, NY
Minimizing Immunosuppressive Effects of Photon and Proton Radiation Therapy on Circulating Lymphocytes L. Basler,1 N. Andratschke,1 S. Ehrbar,1 G. Lucconi,2 A. Bolsi,2 A. Lomax,2 D.C. Weber,2 M. Guckenberger,1 and S. Tanadini-Lang1; 1 University Hospital Zuerich, Zuerich, Switzerland, 2Paul Scherrer Institute, Villigen, Switzerland
Purpose/Objective(s): The majority of pediatric patients diagnosed with advanced-stage neuroblastoma die from their disease despite intensive multimodality therapy. Combination stereotactic body radiation therapy (SBRT) and immune checkpoint inhibition (ICI) represents a promising therapeutic avenue. We sought to develop a highly reproducible, syngeneic mouse model of advanced-stage neuroblastoma, in order to investigate the effects of combination SBRT/ICI on local control and the tumor immune microenvironment. Materials/Methods: We prepared an intrarenal tumorgraft model using the 9464D cell line, derived from the TH-MYCN transgenic neuroblastoma mouse. Following tumor implantation, mice were randomized to SBRT versus sham RT, as well as concurrently dosed anti-PD-1 antibody (aPD1) versus isotype control. SBRT fractions were delivered using the Small Animal Radiation Research Platform in 360 degree axial arcs to minimize normal tissue toxicity. Given increased radioresistance of 9464D relative to human neuroblastoma cell lines, three 8-Gy fractions were delivered. Tumor volume was monitored via CT and 3D ultrasound. Quantitative multiplex immunohistochemistry (qmIHC) staining was performed for
Purpose/Objective(s): Tumor immune escape may be a major reason for failure of immunotherapy and has been shown to be potentially overcome by radiotherapy. However, radiation also has detrimental effects on tumor infiltrating and circulating lymphocytes (CLs). This in silico planning study aimed to model the low-dose effects of photon- and proton-irradiation on CLs depending on dose, fractionation and treatment technique in the context of cancer immunotherapy. Materials/Methods: A model has been implemented in MATLAB to estimate the dose delivered to CLs during stereotactic body radiotherapy of a liver metastasis treated with 3 x 15 Gy. Three scenarios were evaluated, with a virtual liver metastasis positioned at different intra-hepatic locations. Six photon and two proton treatment plans were generated for each location: Volumetric modulated arc therapy (VMAT) and 3D conformal radiotherapy (3DCRT) with and without flattening filter, and proton radiotherapy with either single field uniform dose (SFUD) or intensity modulated proton therapy (IMPT) techniques using a pencil beam scanning delivery paradigm. Cumulative dose to CLs was calculated using a DVH based convolution algorithm. It considers the hepatic blood flow and velocity, hepatic transition time, total body blood volume, heart-to-heart circulation time, treatment delivery time, dose rate and beam energy. A dose of 0.5Gy was considered effective in inactivating or killing CLs.
Abstract 3374 Treatment modality
Beam energy
Flattening filter
3DCRT 3DCRT 3DCRT VMAT VMAT VMAT Proton IMPT Proton SFUD
10 MV 6 MV 6 MV 10 MV 6 MV 6 MV
FFF FFF FF FFF FFF FF
Dose rate 2400 MU/min 1400 MU/min 600 MU/min 2400 MU/min 1400 MU/min 600 MU/min
Number of fields/arcs
Total BOT
MLD
CL0.5
7 7 7 2 3 4 2 2
57 s 111 s 253 s 74 s 147 s 363 s 78 s 71 s
4.3 4.3 4.3 3.8 3.7 3.7 2.7 2.4
15,2% 22,9% 29,9% 18,5% 23,0% 24,1% 11,8% 9,8%
Gy Gy Gy Gy Gy Gy Gy Gy
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International Journal of Radiation Oncology Biology Physics
Results: Mean liver dose (MLD) was mostly influenced by treatment modality: lowest values were achieved with protons followed by VMAT and 3DCRT. In contrast, the proportion of CLs receiving 0.5Gy (CL0.5) was mostly influenced by beam-on time (BOT), which is associated with photon energy and dose rate. 7-field 3D-CRT with 10MV FFF followed by VMAT with 10MV FFF resulted in lowest mean CL0.5 values of 15.2% and 18.5% (Table). 2-field proton plans further reduced CL0.5 to 9.8% for the SFUD and 11.8% for the IMPT plan. Additionally, metastasis location influenced CL0.5, with a mean of 16.2% (8.8 - 23.5%) for the apical, 15.8% (7.9 25.9%) for the basal and 26.2% (12.8 - 40.2%) for the central location. Conclusion: A model has been established to estimate immunosuppressive effects of radiotherapy through inactivation of circulating lymphocytes. In contrast to our initial assumption that integral dose might be the most important factor influencing the proportion of lymphocytes receiving >0.5 Gy, treatment delivery time had the strongest impact: best CL-sparing was achieved with 10MV FFF VMAT and 3D photon techniques with proton radiotherapy further improving lymphocyte sparing. Author Disclosure: L. Basler: None. N. Andratschke: None. S. Ehrbar: None. G. Lucconi: None. A. Bolsi: None. A. Lomax: None. D.C. Weber: None. M. Guckenberger: None. S. Tanadini-Lang: None.
Author Disclosure: C. Bergom: None. B. Fish: None. T. Gasperetti: None. R.A. Schlaak: None. A. Frei: None. M. Medhora: Advisor; Positive Bioscience, Mumbai, India.
3375 Identifying Genetic Variants that Enhance the Therapeutic Ratio of Radiation C. Bergom, B. Fish, T. Gasperetti, R.A. Schlaak, A. Frei, and M. Medhora; Medical College of Wisconsin, Milwaukee, WI Purpose/Objective(s): Radiation therapy (RT) is used by more than 60% of cancer patients, but RT is typically not personalized based upon tumor sensitivity or normal tissue sensitivity biomarkers. RT doses are often constrained so the risk of severe damage to adjacent normal tissues (e.g. heart, lungs, kidneys) is <5-10%, meaning that in over 90% of patients it may be possible to dose escalate RT to the tumor without unacceptable side effects if predictive biomarkers for normal tissue toxicity were available. Our goal is to identify genetic factors that will allow more personalized and effective RT or drug targets for mitigation or protection of normal tissue injuries. Materials/Methods: To demonstrate the impact of host genetic differences on normal tissue RT toxicity, we utilized consomic rat models. Chromosome 3 from the Brown Norway (BN) rat strain was introgressed by repeated back crossing into a SS-Dahl (SS) background to derive the strain SS.BN3. Host factors in the SS.BN3 strain have been shown to alter the RT sensitivity of breast tumors when compared to the SS strain. Congenic rats with only a small (36 megabase, Mb) region of chromosome 3 from SS rats were used to genetically map the phenotypes. Eight-week-old female rats were treated with 13 Gy whole thorax RT or 12.5 Gy total body RT with bone marrow rescue, and animals were examined for radiation pneumonitis and nephropathy. Blood urea nitrogen (BUN) levels were obtained in the total body RT group. Survival curves were analyzed using Kaplan Meier method and log-rank test. Results: The SS.BN3 consomic rats demonstrated protection against lung and kidney RT toxicity compared to SS rats. In rats receiving total body RT, there was a significant and dramatic improvement in survival, with all SS rats (nZ9) morbid due to renal damage by day 140, while no SS.BN3 rats were morbid (p<0.01). At 120 days post RT, the median BUN level in SS rats was >120 mg/ dl versus within normal limits for the SS.BN3 rats. In rats administered whole thorax RT, more SS rats were morbid due to lung toxicity 50-80 days after RT, while SS.BN3 rats demonstrated little lung toxicity. Preliminary results suggest the radioprotective phenotype maps to a w36 Mb region containing genes important for vasculogenesis. The SS.BN3 rats had previously been demonstrated to have abnormal blood vessels and conferred enhanced RT tumor radiosensitivity due to tumor microenvironmental factors. Conclusion: Taken together, the consomic rat models present a novel system to genetically map variants that protect against normal tissue RT toxicity and enhance tumor RT responses. Our data suggest genetic variant(s) on rat chromosome 3 both protect normal tissues and enhance tumor responses to improve the therapeutic ratio for RT. Future work will identify these genes for therapeutic targeting and better prediction of RT responses.
3376 Comprehensive mRNA Prognostic Biomarker Analysis of Grade 2/3 Gliomas S. Beyer,1 E.H. Bell,1 J. McElroy,2 O. Oehlke,3 J. Fleming,1 A. Becker,1 O. Staszewski,3 M. Prinz,3 A. Grosu,4 and A. Chakravarti1; 1The Ohio State University, Columbus, OH, 2The Ohio State University, Center for Biostatistics, Columbus, OH, 3University of Freiburg, Freiburg, Germany, 4 Department of Radiation Oncology, University Medical Center Freiburg, Freiburg, Germany Purpose/Objective(s): Grade II and III gliomas exhibit variable prognoses and responses to chemotherapy and radiation. Gliomas have traditionally been categorized according to grade and histology, however predicting prognosis and treatment response with this classification system is challenging. The World Health Organization released a new classification system for gliomas based on histology and molecular biomarkers, including isocitrate dehydrogenase (IDH) mutations and 1p/19q co-deletions, thus improving our ability to predict tumor prognosis. Previous studies have revealed prognostic molecular subgroups, including IDH wild-type, IDH mutant/1p/19q intact and IDH mutant/1p/19q co-deleted. Our study aims to identify prognostic biomarkers of Grade II/III gliomas that are independent of IDH and 1p/19 status by mRNA profiling. Materials/Methods: We established a clinical database of 58 Grade II (nZ19) and III (nZ38) gliomas from Freiburg, Germany, with corresponding tissue. We extracted RNA from formalin-fixed paraffin embedded (FFPE) Grade II/III glioma tissues and utilized the Affymetrix HTA ClariomD array. Normalization (RMA) and summarization were carried out using Affymetrix transcriptome analysis console software. Cox regression analysis identified mRNA expression significantly associated with overall survival (OS). Over-represented signaling pathways were identified by Ingenuity Pathway Analysis. Results: Our analysis identified 6,998 probe sets significantly associated with OS (p<0.05) independent of IDH mutation status, 1p/19q co-deletion status and age. 4,643 probe sets corresponded to protein-coding genes (2,443 with high hazard ratio (HR) and 2,200 with low HR). Conclusion: Axon guidance signaling and invasion/cell migration pathways were over-represented among genes associated with decreased OS (high HR) independent of IDH and 1p/19q status. Pathways involving lymphocyte/chemokine signaling were over-represented among genes associated with increased OS (low HR). An analysis of predictive biomarkers is currently ongoing to identify gene expression associated with treatment response among gliomas (surgery alone, adjuvant RT, or adjuvant chemotherapy) and will be presented at the annual ASTRO meeting. Future studies will include a larger institutional cohort of gliomas for validation of these prognostic and predictive biomarkers in addition to functional characterization of biomarkers in vitro. Author Disclosure: S. Beyer: Employee; The Ohio State University. E.H. Bell: None. J. McElroy: Employee; The Ohio State University. O. Oehlke: None. J. Fleming: None. A. Becker: None. O. Staszewski: None. M. Prinz: None. A. Grosu: None. A. Chakravarti: None.
3377 Targeted Inhibition of PI3K and MEK in Combination With Radiation Therapy in UT15: A Murine Model of Head and Neck Squamous Cell Carcinoma K.G. Blas Jr,1 S. Galoforo,2 T.G. Wilson,2 S.A. Krueger,3 I.S. Grills,4 B. Marples,5 and G.D. Wilson4; 1Beaumont Health, Royal Oak, MI, 2 Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI, 3MI Bioresearch, Ann Arbor, MI, 4Department of Radiation Oncology, Beaumont Health System, Royal Oak, MI, 5University of Miami Miller School of Medicine, Department of Radiation Oncology, Miami, FL