Even though doctors sometimes skip bone marrow exams during clinical trials, a Mayo Clinic study discovered that they are crucial after experimental multiple myeloma treatments. Other standard tests for multiple myeloma patients’ responses to treatments can give false positives if used alone. The study was published in the journal Blood in late July.

Whether the study’s findings will apply to patients not in clinical trials is up for debate. However, the findings are very important to doctors doing clinical trials with patients, wrote Dr. S. Vincent Rajkumar, lead researcher of the study, in an e-mail to the Myeloma Beacon. Clinical trials depend on all researchers reporting complete response in the same way, so that scientists can compare treatments studied under different trials. Rajkumar’s research confirms the need for bone marrow exams to report complete response.

Bone marrow exams -- either aspirations or biopsies -- look for the amount of plasma cells in the bone marrow. In their published paper, the Mayo Clinic scientists wrote that the exams can be cumbersome and uncomfortable for patients, so some doctors skip them.

The current standard is for doctors to perform three lab tests to see how well their patients are faring after experimental treatment: a bone marrow exam, serum immunofixation, and urine immunofixation. Some doctors argue that just doing serum and urine immunofixation is enough because if those results show that a patient has completely responded to his or her treatment, then it is unlikely that bone marrow exam results will show otherwise.

Before the study, “many, including me, felt that the bone marrow requirement may not be needed, and it basically put patients through an unnecessary procedure,” wrote Rajkumar.

However, his research found that this notion was incorrect, and that doctors should continue performing all three tests.

Rajkumar and his colleagues examined data from 92 people with treated multiple myeloma. The data came from 1995 and afterwards. The study participants all had good results from serum and urine immunofixation and had a bone marrow exam within 30 days of their immunofixation tests. In 14 percent of these people, bone marrow exams showed that they still had five percent or more plasma cells. This result meant that they did not completely respond to treatment, even though their serum and urine immunofixation results showed improvement.

Rajkumar emphasized that the study was geared towards doctors in research settings. The study was not designed to test whether patients who are not in clinical trials need bone marrow exams. “That is a separate, controversial issue,” Rajkumar wrote.

Nevertheless, the study’s results showed it may be important for doctors to know their patients’ plasma cell amounts because these amounts are correlated with survival times. After they achieved good serum and urine immunofixation results, the study participants who had less than five percent plasma cells on average lived significantly longer than those who had five percent or more plasma cells. However, there was no significant difference in how long the people in these two groups lived after their initial diagnosis.

Researchers also found that adding another exam that looked at free light chains did not make the results more accurate. Ten percent of their study participants with normal results from a free light chain exam still had five percent or more plasma cells in their bone marrow.

The study paper recommended that others research what happens when doctors keep treating patients who have good serum and urine immunofixation results, but have five percent or more plasma cells. This can help these patients fully recover their blood function and improve survival rates.

For more information, please see the article in the journal Blood.