Browsing by Author "Ko, Ryan"

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    Abdominal FLASH irradiation reduces radiation-induced gastrointestinal toxicity for the treatment of ovarian cancer in mice
    (Springer Nature, 2020-12-10) Levy, Karen; Natarajan, Suchitra; Wang, Jinghui; Chow, Stephanie; Eggold, Joshua T.; Loo, Phoebe E.; Manjappa, Rakesh; Melemenidis, Stavros; Lartey, Frederick M.; Schüler, Emil; Skinner, Lawrie; Rafat, Marjan; Ko, Ryan; Kim, Anna; Al-Rawi, Duaa H.; von Eyben, Rie; Dorigo, Oliver; Casey, Kerriann M.; Graves, Edward E.; Bush, Karl; Yu, Amy S.; Koong, Albert C.; Maxim, Peter G.; Loo, Billy W., Jr.; Rankin, Erinn B.; Radiation Oncology, School of Medicine
    Radiation therapy is the most effective cytotoxic therapy for localized tumors. However, normal tissue toxicity limits the radiation dose and the curative potential of radiation therapy when treating larger target volumes. In particular, the highly radiosensitive intestine limits the use of radiation for patients with intra-abdominal tumors. In metastatic ovarian cancer, total abdominal irradiation (TAI) was used as an effective postsurgical adjuvant therapy in the management of abdominal metastases. However, TAI fell out of favor due to high toxicity of the intestine. Here we utilized an innovative preclinical irradiation platform to compare the safety and efficacy of TAI ultra-high dose rate FLASH irradiation to conventional dose rate (CONV) irradiation in mice. We demonstrate that single high dose TAI-FLASH produced less mortality from gastrointestinal syndrome, spared gut function and epithelial integrity, and spared cell death in crypt base columnar cells compared to TAI-CONV irradiation. Importantly, TAI-FLASH and TAI-CONV irradiation had similar efficacy in reducing tumor burden while improving intestinal function in a preclinical model of ovarian cancer metastasis. These findings suggest that FLASH irradiation may be an effective strategy to enhance the therapeutic index of abdominal radiotherapy, with potential application to metastatic ovarian cancer.
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    Reduced cognitive deficits after FLASH irradiation of whole mouse brain are associated with less hippocampal dendritic spine loss and neuroinflammation
    (Elsevier, 2019-10) Simmons, Danielle A.; Lartey, Frederick M.; Schüler, Emil; Rafat, Marjan; King, Gregory; Kim, Anna; Ko, Ryan; Semaan, Sarah; Gonzalez, Selena; Jenkins, Melissa; Pradhan, Pooja; Shih, Zion; Wang, Jinghui; Eyben, Rievon; Graves, Edward E.; Maxim, Peter G.; Longo, Frank M.; Loo, Billy W., Jr.; Radiation Oncology, School of Medicine
    Aim To evaluate the impact of ultra-rapid FLASH mouse whole brain irradiation on hippocampal dendritic spines and neuroinflammation, factors associated with cognitive impairment after brain irradiation. Methods We administered 30 Gy whole brain irradiation to C57BL6/J mice in sub-second (FLASH) vs. 240 s conventional delivery time keeping all other parameters constant, using a custom configured clinical linac. Ten weeks post-irradiation, we evaluated spatial and non-spatial object recognition using novel object location and object recognition testing. We measured dendritic spine density by tracing Golgi-stained hippocampal neurons and evaluated neuroinflammation by CD68 immunostaining, a marker of activated microglia, and expression of 10 pro-inflammatory cytokines using a multiplex immunoassay. Results At ten weeks post-irradiation, compared to unirradiated controls, conventional delivery time irradiation significantly impaired novel object location and recognition tasks whereas the same dose given in FLASH delivery did not. Conventional delivery time, but not FLASH, was associated with significant loss of dendritic spine density in hippocampal apical dendrites, with a similar non-significant trend in basal dendrites. Conventional delivery time was associated with significantly increased CD68-positive microglia compared to controls whereas FLASH was not. Conventional delivery time was associated with significant increases in 5 of 10 pro-inflammatory cytokines in the hippocampus (and non-significant increases in another 3), whereas FLASH was associated with smaller increases in only 3. Conclusion Reduced cognitive impairment and associated neurodegeneration were observed with FLASH compared to conventional delivery time irradiation, potentially through decreased induction of neuroinflammation, suggesting a promising approach to increasing therapeutic index in radiation therapy of brain tumors.