A new approach to treating this intractable cancer delivers a one-two punch that achieved complete remission lasting longer than 4 years in 72% of the patients studied. The researchers from Wiell Cornell Medical Center and the Center for Lymphoma and Myeloma, both in New York, N.Y., and Corixa Corp., San Francisco, California, presented their findings today at the Society of Nuclear Medicine's 51st Annual Meeting in Philadelphia.
Although follicular lymphoma cancer cells are very sensitive to radiation treatment, radiation therapy is impractical because there is no clear target. The cancer sites are widespread, and some of them may be so small that they are undetectable. The standard treatment for this type of non-Hodgkin's lymphoma is chemotherapy and, recently, non-radiolabeled monoclonal antibodies; unfortunately, because the standard therapies do not kill all cancer cells, the cancer usually recurs within a few years. Subsequent chemotherapy sessions tend to be less and less effective.
The new approach combines radioimmunotherapy with conventional chemotherapy, which may augment the antitumor effects of either treatment alone. First, a course of conventional chemotherapy kills many of the cancer cells and shrinks the tumors; then, rather than wait for the almost inevitable relapse, radioimmunotherapy is administered several weeks later to deliver the knockout punch.
Radioimmunotherapy is a new type of cancer treatment. A radioactive isotope of iodine (iodine-131) is attached to a molecule designed to seek out proteins on the surface of the cancer cells (a monoclonal antibody). The monoclonal antibody carries the radiation straight to the remaining cancer cells, where the radioactive iodine delivers a lethal dose of radiation at the cellular level with minimal damage to surrounding tissues.
The advantage of following chemotherapy closely with molecularly targeted radiation therapy may be that, with many or most cancer cells destroyed by the chemotherapy, the full force of the radioactivity is concentrated on the few remaining cancerous cells.
For the study, 35 patients with untreated follicular non-Hodgkin's lymphoma were administered three cycles of fludarabine. Six to eight weeks following the last round of chemotherapy, when the patients had recovered from the expected side effects of chemotherapy, the researchers administered the Bexxar treatment. Bexxar (from Corixa Corporation) consists of the monoclonal antibody, tositumomab, labeled with idodine-131.
All patients completing the therapy showed at least a partial response, and 83% achieved complete remission. With standard treatment, up to 60% of patients achieve a complete response, and most relapse within 3 years. In this study, 72% of all patients treated are still in complete remission 4.4 years later. While there is no "control" group in this phase II study, these findings compare favorably to standard treatment regimens for this patient population.
According to one of the authors of the study, Lale Kostakoglu, MD, "the results are very encouraging. We feel that the further evaluation of the addition of RIT to chemotherapeutic regimens for patients with follicular lymphoma is warranted. This may be the future of treatment with radiolabeled antibodies."