by Gregory M. Vogel
For the first time, a targeted radiation treatment called helical TomoTherapy is being combined with other therapies to treat multiple myeloma. Results of the study by City of Hope Cancer Center researchers were presented at the American Society of Hematology’s 47th annual meeting in December.
Each year, approximately 16,000 Americans are diagnosed with multiple myeloma, a disease in which cancerous blood plasma cells proliferate in bone marrow, forming malignant tumors that crowd out other important cells. Standard treatments include high-dose chemotherapy with or without fractionated total body irradiation (FTBI), but both cause serious side effects. To reduce these side effects, patients can be supplemented with their own peripheral blood progenitor cells (PBPC). Despite advances in the field, long-term prospects still remain poor: 80 percent of patients given a tandem high-dose chemotherapeutic regimen of melphalan with or without FTBI and PBPC relapse after seven years.
By itself, FTBI kills myeloma cells, but it can harm important organs, including the heart, eyes, intestines, lungs and liver. Combining melphalan with FTBI is highly toxic, and results are no better than melphalan alone.
A research team led by George Somlo, M.D., director, Myeloma Program in the Department of Hematology & Hematopoietic Cell Transplantation, and Jeffery Wong, M.D., chair, Department of Radiation Oncology, began a trial investigating the effectiveness of helical TomoTherapy with melphalan.
To date, three patients have received 1,000 centigrays (cGy) of radiation. In the first two patients, the amount of radiation delivered to sensitive nontarget organs showed a 2.5-fold median decrease in comparison to radiation delivered to the bone marrow; the third patient is just recovering from the procedure. Side effects so far were moderate.
While it is too early to report on the outcome of the treatment, results of the trial indicate that helical TomoTherapy may enable the delivery of total marrow irradiation at high doses to treat multiple myeloma while avoiding collateral toxicities.
In the next phase of research, scientists plan to raise the TMI radiation level by 20 percent to 1,200 cGy.
Researchers participating in the study include Stephen J. Forman, M.D., Amrita Krishnan, M.D., Leslie Popplewell, M.D., and Pablo Parker, M.D., all of the Department of Hematology & Hematopoietic Cell Transplantation; Tim Schultheiss, Ph.D., and An Liu, Ph.D., of the Department of Radiation Physics; and Firoozeh Sahebi, M.D., City of Hope-Southern California Kaiser Permanente Regional Bone Marrow Transplant Program.