P.R. Patel

Application of a Novel Murine Ear Vein Model to Evaluate the Effects of a Vascular Radioprotectant on Radiation-Induced Vascular Permeability and Leukocyte Adhesion

Vascular injury after radiation exposure contributes to multiple types of tissue injury through a cascade of events. Some of the earliest consequences of radiation damage include increased vascular permeability and promotion of inflammation, which is partially manifested by increased leukocyte-endothelial (L/E) interactions. We describe herein a novel intravital imaging method to evaluate L/E interactions, as a function of shear stress, and vascular permeability at multiple time points after local irradiation to the ear. This model permitted analysis of quiescent vasculature that was not perturbed by any surgical manipulation prior to imaging. To evaluate the effects of radiation on vascular integrity, fluorescent dextran was injected intravenously and its extravasation in the extravascular space surrounding the ear vasculature was measured at days 3 and 7 after 6 Gy irradiation. The vascular permeability rate increased approximately twofold at both days 3 and 7 postirradiation (P < 0.05). Leukocyte rolling, which is indicative of L/E interactions, was significantly increased in mice at 24 h postirradiation compared to that of nonirradiated mice. To assess our model, as a means for assessing vascular radioprotectants, we treated additional cohorts of mice with a thrombopoietin mimetic, TPOm (RWJ-800088). In addition to stimulating platelet formation, thrombopoietin can protect vasculature after several forms of injury. Thus, we hypothesized that TPOm would reduce vascular permeability and L/E adhesion after localized irradiation to the ear vasculature of mice. If TPOm reduced these consequences of radiation, it would validate the utility of our intravital imaging method. TPOm reduced radiation-induced vascular leakage to control levels at day 7. Furthermore, L/E cell interactions were also reduced in irradiated mice treated with TPOm, compared with mice receiving irradiation alone, particularly at high shear stress (P = 0.03, Kruskal-Wallis). We conclude that the ear model is useful for monitoring quiescent normal tissue vascular injury after radiation exposure. Furthermore, the application of TPOm, for preventing early inflammatory response created by damage to vascular endothelium, suggests that this drug may prove useful in reducing toxicities from radiotherapy, which damage microvasculature that critically important to tissue function.

Development and Preliminary Evaluation of a Murine Model of Chronic Radiation-Induced Proctitis

PURPOSEnRadiotherapy (RT) is commonly used to treat most pelvic malignancies. While treatment is often effective, curative radiation doses to the rectum can result in chronic radiation-induced proctitis, which is characterized by diarrhea, tenesmus, and/or rectal bleeding, recently termed pelvic radiation disease. An animal model of chronic radiation-induced proctitis would be useful to test both preventative and therapeutic strategies to limit this morbidity but has been elusive because of the high rodent mortality associated with acute bowel RT injury. The objective of this research was to develop a novel mouse model of chronic radiation-induced proctitis using advanced technology.nnnMETHODS AND MATERIALSnUsing an X-RAD 225-Cx (Precision X-Ray) small animal irradiator, multiple plan configurations were evaluated for planning treatment volume and organ-at-risk avoidance to deliver a 15xa0Gy 3D conformal treatment plan. The final plan was verified by high resolution 3D dosimetry (PRESAGE/optical-CT), and delivered using a single arc. Mice were monitored for mortality for 250xa0days, followed by histopathological correlates including mucicarmine, Massons trichrome, and fecal pellet length.nnnRESULTSnSix beam arrangements were considered: single and parallel-opposed fields with whole-pelvis coverage, and collimated fields in parallel-opposed, 3-field, 4-field, and arc geometries. A collimated arc plan offered superior planning treatment volume coverage and organ-at-risk avoidance compared to whole-pelvis irradiation. Treatment verification with PRESAGE 3D dosimetry (Heuris Inc) showed >99% of voxels passing gamma analysis with 2%/2xa0mm criteria. Our treatment resulted in no acute mortality and 40% mortality at 250xa0days. Histopathological analysis showed increased mucous production and fibrosis of the irradiated colon, but no change in fecal pellet length.nnnCONCLUSIONSnOur model was able to target successfully lower colon and rectum with lower mortality than other published models. This permitted measurement of late effects that recapitulate some features of rectal damage in humans.

Carcinoma of the ampulla of Vater: Patterns of failure after resection and benefit of adjuvant radiotherapy.

254 Background: Ampullary carcinoma is a rare malignancy. Despite radical resection, survival rates remain low with high rates of local failure. To define the role of radiation therapy and chemotherapy with surgery, we performed a single institution analysis of treatment- related outcomes.nnnMETHODSnA retrospective analysis was performed of all patients undergoing potentially curative therapy for adenocarcinoma of the ampulla of Vater at Duke University Hospitals between 1975 and 2009. Local control (LC), overall survival (OS), disease-free survival (DFS), and metastases-free survival (MFS) were estimated using the Kaplan-Meier Method.nnnRESULTSnOne hundred thirty-seven patients with ampullary carcinoma underwent potentially curative pancreaticoduodenectomy. Sixty-one patients undergoing resection received adjuvant (n= 43) or neoadjuvant (n=18) radiation therapy with concurrent chemotherapy (CRT). Patients receiving radiotherapy were more likely to have poorly differentiated tumors. Median radiation dose was 50 Gy. Median follow up was 8.8 years. Of patients receiving neoadjuvant therapy, 67% were downstaged on final pathology with 28% achieving pathologic complete response. Three-year local control was significantly improved in patients receiving CRT (88% vs. 55% p= 0.001) with trend toward a 3-year OS benefit in patients receiving CRT (62% vs. 46% p=0.074). Despite this, there was no significant difference in 3-year DFS (66% CRT vs 48% surgery alone p=0.09) or MFS (69% CRT vs 63% surgery alone p=0.337).nnnCONCLUSIONSnLong term survival rates are low. Local failure rates are high following radical resection alone and improved with CRT. Despite more adverse pathologic features in patients receiving CRT, survival outcomes were at least equivalent with a trend toward statistical significance. Given the patterns of relapse with surgery alone and local control benefit in patients receiving CRT, the use of chemoradiotherapy in selected patients should be considered. No significant financial relationships to disclose.