About Radioimmunotherapy (RIT)
Radioimmunotherapy or RIT is an exciting and relatively new personalized cancer treatment that combines the cancer killing of radiation therapy with the precise targeting capacity of immunotherapy. In RIT, a tumor-killing dose of a radioactive substance is linked to a monoclonal antibody that targets and binds selectively to a malignant tumor (cancer) when injected into the body. The ability of the antibody to bind to a tumor-associated antigen (a molecule that can stimulate an immune response) ensures that the tumor gets a high dose of radiation, which can kill the targeted cancer cells and nearby cancer cells, while normal tissue gets only a minimal dose. This minimizes toxicity to normal tissues.
RIT Product Examples
The two FDA approved RIT regimens are Zevalin (approved by FDA in 2002) and Bexxar (approved by FDA in 2003).
Zevalin and Bexxar were the first FIT agents approved for the treatment of patients whose non-Hodgkins lymphoma (NHL) proved unresponsive or resistant (refractory) to conventional chemotherapy. NHL is a cancer in which abnormal white blood cells (lymphocytes) emerge and divide uncontrollably, often growing first in lymph nodes and then growing widely throughout the body, and if unsuccessfully treated, leading to organ dysfunction and death. Non-Hodgkin's lymphoma is the sixth most frequently occurring cancer in the United States and afflicts half a million people in the US.
RIT also has therapeutic potential for other types of cancers, including prostate cancer, metastatic melanoma, ovarian cancer, leukemia, high-grade brain tumors, metastatic colorectal cancer and neoplastic meningitis.
Benefits of RIT
Chemotherapy, currently the most common and widely known treatment for cancer, is a non-targeted therapy that kills not only cancer cells but normal, healthy cells, as well. This leads to severe side effects for patients including nausea, vomiting, hair loss, diminished white blood cell and platelet counts, and severe loss of energy. Chemotherapy is typically given over many months. By contrast, RIT has fewer, less severe side effects than chemotherapy and has the ability to directly target and kill the cancer cells. This is why this new generation of cancer treatment is appropriately referred to as targeted therapy. Researchers have found that RIT increases the ability of the therapy to target and eradicate tumors throughout the body, offering promise to patients who nearly lost hope when their chemotherapy treatments proved ineffective. And whereas chemotherapy necessitates enduring weeks or months of harsh and disabling treatments, RIT is administered in only a few doses over a two-week period.
Track Record of Success
While we won’t know for a few more years whether or not patients have been completely cured, Zevalin and Bexxar tend to work very well for most lymphoma patients in whom they are indicated. Initial indicators are positive as some patients appear to have been cured, and virtually all of them will live longer because of their RIT treatments. According to one clinical trial, patients with follicular lymphoma who received standard treatment achieved remission 36 percent of the time. Yet, when Zevalin was added, the remission rate soared to 89 percent. Disease free survival was prolonged by two years using Zevalin in a recent randomized trial of over 400 patients, leading the European Regulatory Authorities to grant approval 4-28-08 for Zevalin therapy as a key component of treatment of follicular lymphoma. In a separate study, Bexxar produced at least some response in 97 percent of patients. Zevalin and Bexxar are particularly essential for older patients who cannot handle a stem cell transplant.
Despite all its promising benefits and its proven record of saving thousands of lives, RIT is not as widely utilized as it could or should be. Dr. Bruce Cheson, Professor of Medicine and Director of Hematology Research at the Lombardi Comprehensive Cancer Center at Georgetown University Hospital says, "RIT is the most effective, least used treatment in oncology."
The Bottom Line
Radioimmunotherapy (RIT) is a proven cancer treatment that significantly extends the lives of cancer patients, especially those with non-Hodgkin’s lymphoma. Molecular imaging plays a major role in this personalized therapy. For the sake of hundreds of thousands of patients with lymphoma, highly-effective RIT medicines such as Zevalin and Bexxar must be reimbursed at a level that allows patients adequate access.