Lab tests used to evaluate treatment response after a stem cell transplant for multiple myeloma could lead physicians to wrongfully believe that a patient is having a relapse, according to researchers from the Medical College of Georgia at Augusta University.
The tests under scrutiny are three types of analyses to evaluate antibodies produced by cancerous plasma cells, the cause of myeloma.
In contrast to healthy plasma cells that produce an array of different antibodies, cancerous ones produce only one type of antibody, which is easily distinguished by these tests. But the research team discovered that patients who had stem cell transplants had a transient increase in a group of highly similar antibodies that looks very similar to the appearance of the single-antibody signal.
The similarity could lead physicians to believe that a patient is having a relapse. Researchers call this type of signal an oligoclonal pattern, or band.
The study, “Oligoclonal Pattern/Abnormal Protein Bands in Post-Treatment Plasma Cell Myeloma Patients: Implications for Protein Electrophoresis and Serum Free Light Chain Assay Results,” appeared in the Journal of Clinical Medicine Research.
“We want to emphasize that oligoclonal bands should mostly be recognized as a response to treatment and not be mistaken as a recurrence of the original tumor,” Dr. Gurmukh Singh, vice chair of clinical affairs at the Department of Pathology and Walter L. Shepeard Chair in Clinical Pathology at Augusta University, said in a press release.
The three examined tests separate proteins into groups based on their electrical charge. The team discovered that the group of antibodies that doctors might confuse for a recurrence more often appears in people who had a stem cell transplant, compared to those treated with chemotherapy.
Among 251 patients in the study, 159 had autologous stem cell transplants. Researchers found the deceiving signal in 57.9% of transplanted patients compared to only 8.8% among those who had chemotherapy.
More than half of these signals appeared within the first year of a transplant. But the range was wide, with some patients showing such oligoclonal patterns within two months, and others only five years after the treatment.
These bands disappear over time, but doctors risk misinterpreting them as a relapse. To determine if cancer really has recurred, Singh said it is crucial to consider the location of the signal in the analysis.
“If the original peak was at location A, now the peak is location B, that allows us to determine that it is not the same abnormal, malignant antibody,” Singh said.
“If the location is different, this is just a normal response of recovery of the bone marrow that could be mistaken for recurrence of the disease,” he added, noting that these signals can also appear during an infection.