Radiation therapy is a highly effective means to kill cancer cells;unfortunately tumors can grow back from small pockets of residual disease. We propose that immune responses initiated by radiation therapy have the potential to control residual disease in the treatment site and distant metastases. Our research thus far has demonstrated three main points: first, that radiation therapy induces tumor antigen-specific T cell responses that are required for the full efficacy of radiation therapy;second, that high dose radiation therapy releases adjuvants that are required to prime adaptive responses to tumor antigens;and third, a negative fact, that the tissue repair response activated by radiation damage limits immune responses at the tumor.
The aim of this proposal is to understand the relationship between radiation dose and the positive and negative immune responses to tumors. We hypothesize that hypofractionated radiation therapy would result in superior adaptive immune responses to tumor antigens. We further examine how radiation interacts with immunotherapies to extend inflammation in the tumor and target residual disease.
The specific aims of this study are to 1: Test the hypothesis that hypofractionated radiation therapy would result in superior adaptive immune responses to tumor antigens;2: Test the hypothesis that vaccine therapies synergize with hypofractionated radiation therapy to boost and target T cell responses, and extend inflammatory destruction in the tumor;3: Test the hypothesis that hypofractionated radiation therapy is a superior partner for clinical vaccine therapies in neoadjuvant chemoradiation for pancreatic cancer. Our study design incorporates preclinical radiation therapy of spontaneous models of pancreatic cancer using an advanced imaging and treatment platform. In addition, we use two matching clinical studies of immunomodulation combined with neoadjuvant chemoradiation therapy for locally advanced and borderline resectable pancreatic cancer to examine the effect of radiation fractionation on T cell immune responses. We and others are designing and conducting clinical studies combination immunotherapy and radiation: these data will be key to the design of an effective combination.

Public Health Relevance

Cancer patients are treated with effective cytotoxic therapies that can reduce the tumor to few viable cancer cells: unfortunately for cancer patients, tumors can recur from small pockets of residual disease. Killing cancer cells using high dose radiation therapy provides an opportunity to prime adaptive immune responses to target this residual disease. This proposal uses an advanced preclinical model and clinical studies to determine whether high dose radiation therapy can more effectively target adaptive immune responses to the tumor than conventionally fractionated radiation.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Radiation Therapeutics and Biology Study Section (RTB)
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Ahmed, Mansoor M
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Providence Portland Medical Center
United States
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