The Department of Radiation Oncology is investigating a new type of radiation therapy that targets radiation to the tumor using monoclonal antibodies (MAbs). This form of therapy is called radioimmunotherapy (RIT).
The nationally-recognized, multidisciplinary RIT program began at City of Hope 16 years ago. Currently funded by a number of grants from the National Cancer Institute, researchers are investigating the use of MAbs -- genetically engineered molecules specifically designed to hone in on cancer cells. Active research efforts within the Department of Radiation Oncology focus on the use of radiolabeled MAbs as a method to target therapeutic amounts of radioisotope through the blood stream directly to the cancer cell.
RIT uses the radioactive metal to Yttrium-90, which delivers higher levels of local radiation to the tumor. The radiolabeled MAb is administered through a vein and then circulates through the body to the surface of tumor cells. The tumor cells are destroyed by the radiation given off from the localized radiolabeled MAbs.
Three different antibodies are being used in our current radiation oncology clinical trials. One binds carcinoembryonic antigen (CEA), a tumor antigen found in certain patients with breast, colon, lung, thyroid and ovarian cancers. The second antibody binds to CD20, an antigen found on the surface of certain lymphomas. The third antibody binds to HER2 (human epidermal growth factor receptor 2) which is overexpressed in approximately 25% of breast cancer patients.
Currently, ongoing clinical trials are investigating the potential utility of genetically engineered, high affinity, radiolabeled monoclonal antibodies to detect and treat disease in patients with colon, lung, breast, and thyroid,as well as leukemias and lymphomas. These trials are evaluating strategies to further improve the therapeutic index of this treatment modality through the addition of chemotherapy agents or through stem cell transplantation.
There has been significant progress made in the treatment of lymphomas and leukemias with radioimmunotherapy. These malignancies are sensitive to radiation and therefore are ideal targets for this form of therapy. Within the next few years, radioimmunotherapy will soon become part of the standard therapies offered to these patients. Investigators are actively evaluating the use of radioimmunotherapy in patients undergoing bone marrow transplantation, to determine whether this form of radiation can complement and/or replace traditional forms of radiation in these patients.
Finally, clinical trials are evaluating the ability of smaller molecular weight, faster clearing antibodies to detect and eventually treat colon, breast, and prostate cancer and other malignancies. These novel faster clearing antibodies are also being evaluated in the laboratory and in the clinic as tools to detect small deposits of tumors using PET imaging. PET is a powerful tool for cancer detection, often detecting tumors that are not detected by other imaging modalities. These agents will help physicians better diagnose and treat disease. In addition, the radiation oncologist using IMRT, CT treatment planning and image fusion technology, will be better able to focus the high dose region to areas of active disease within the tumor.
The Radioimmunotherapy Program is a multidisciplinary effort involving basic and clinical scientists. In addition to Radiation Oncology, other collaborating specialties at City of Hope include:
This collaborative effort is made possible by the unique research environment that City of Hope provides.