Newly Approved Therapy Successfully Targets Non-Hodgkin's Lymphoma

“The approach we took with Bexxar is an innovation,” says Kaminski, co-director of the Leukemia/Lymphoma/Bone Marrow Transplant Program at the U-M Comprehensive Cancer Center. “Prior to Bexxar, most of our treatment strategies were based upon chemotherapy and external beam radiation therapy, which is effective – but not always – and certainly toxic to patients.”

Unlike traditional chemotherapy and radiation, which both kill healthy cells along with the cancer cells, the Bexxar therapeutic regimen uses radiation to target the cancerous cells. Patients receive a single treatment injection, instead of multiple rounds of treatment over several months of chemotherapy, and there are very few side effects.

Kaminski has used Bexxar in clinical trials, but in June the FDA gave it the green light as an approved treatment for non-Hodgkin’s lymphoma that no longer responds to other treatments. In September, Medicare announced it would pay for Bexxar therapeutic regimen.

Non-Hodgkin’s lymphoma is a cancer of the lymph system, which is part of the immune system. Lymphoma spreads easily through the lymph system and the bloodstream and consequently tends to be widespread when it’s diagnosed. There are many different types of non-Hodgkin’s lymphoma and prognosis varies widely.

Bexxar is approved for use in people with follicular lymphoma who have had previous chemotherapy. Bexxar is a dual-action therapy that pairs the tumor-targeting ability of an antineoplastic (cancer killing) monoclonal antibody (Tositumomab) and the therapeutic potential of radiation with patient-specific dosing. Combined, these agents form a radiolabeled monoclonal antibody carried throughout the body that is able to bind to the target antigen found on cancer cells, thereby initiating an immune response against the cancer and delivering a dose of radiation directly to tumor cells. Bexxar is the only non-Hodgkin’s lymphoma therapy that is specifically dosed based on an individual’s drug clearance rate, allowing the delivery of a pre-determined amount of radiation to each patient.

“It turns out that virtually all lymphomas derived from a specific kind of lymphocyte called B-cells have on their cell’s surface a protein called CD20,” explains Kaminski who developed the treatment along with U-M nuclear medicine pioneer Richard Wahl, M.D., now chair of nuclear medicine at Johns Hopkins University Medical Center.

“The antibody that we attach the radio-isotope to recognizes this particular CD20 target, and latches onto it. So when you introduce the antibody into the bloodstream, it’s going to naturally bind to only things or cells that have this target,” Kaminski says.

Once the antibody hooks onto the CD20, the radio-isotopes emit powerful particles that plunge right through the tumor cells, killing off the cancer just in that vicinity.

In addition to sparing the patient from the toxic side effects of chemotherapy, including nausea and hair loss, treatment with Bexxar is quicker than chemotherapy. Where chemotherapy is administered over three to four week cycles for six to eight months, Bexxar treatment occurs within one week.

On the first day of treatment, patients are injected with a test dose of radioactive Bexxar that’s meant to determine how that person’s body processes the tagged antibody. Nuclear medicine scans assess how quickly the Bexxar reaches the tumor and how quickly the radiation disappears from the patient’s body. At that point, oncologists can create an individual Bexxar dose for that patient. The patient receives the therapeutic dose one week after the test injection. In total, the treatment requires four office visits – one for the test dose, two for the nuclear medicine scans, and one for the therapeutic dose.

“The treatment is then finished right after that,” Kaminski says. “There are no repetitive cycles. A patient goes home and the treatment starts to work just as soon as it’s been given.”

About six to eight weeks later, the patient undergoes a CT scan, physical exam and blood work to determine whether the treatment has worked. Doctors can tell at this point if the lymphoma has gone into remission.

Patients who receive Bexxar have already gone through multiple rounds of chemotherapy and in many cases were no longer responding to the conventional drugs used to treat lymphoma. Traditionally, their prognosis would be poor. Within this group, clinical trials found 70 percent of patients responded to Bexxar and 20 percent to 30 percent achieved a complete remission, where no signs of lymphoma are present in imaging tests or biopsy.

“The promise of this treatment is that there will be many more patients living free of disease, without side effects, than ever before,” Kaminski says. “This offers a new option and provides hope for patients who had run out of options.”

Bexxar is marketed in the United States by Corixa Corp. and GlaxoSmithKline.

For more information about cancer treatment and studies at UMHS, call (800) 865-1125. For more information on Bexxar from its manufacturer, visit http://www.bexxar.com or call (877) 4-BEXXAR.

About non-Hodgkin’s lymphoma

• Non-Hodgkin’s lymphoma is the sixth leading cause of cancer deaths.

• It’s divided into two groups: B-cell lymphoma and T-cell lymphoma. More than 85 percent are B-cell lymphoma.

• About 300,000 people in the United States have non-Hodgkin’s lymphoma

• In 2004, an estimated 54,000 to 55,000 new cases will be diagnosed.

• Average age at diagnosis is in the mid-60s, and it affects men more often than women.

• Symptoms include painless swelling of lymph nodes in the neck, underarm or groin. Other signs are night sweats, fatigue, fever, weight loss and red, itchy patches on the skin.

Web resources:

U-M Health Topics A-Z: Non-Hodgkin’s lymphomahttp://www.med.umich.edu/1libr/cancer/leuk05.htm

U-M Comprehensive Cancer Center: Non-Hodgkin’s lymphoma information guide http://www.cancer.med.umich.edu/learn/pwnonhodlymphoma.htm

U-M Comprehensive Cancer Center: Lymphoma Clinichttp://www.cancer.med.umich.edu/clinic/lymphomaclinic.htm

National Cancer Institute: Non-Hodgkin’s lymphoma homepagehttp://www.cancer.gov/cancerinfo/types/non-hodgkins-lymphoma/

American Cancer Society: Learn about cancerhttp://www.cancer.org/docroot/lrn/lrn_0.asp