Sustained Benefit After Two Years From Rare Blood Cancer Drug

Ibrutinib found to control Waldenstrom's Macroglobulinemia in 95% of patients.

A recent FDA-approved treatment for a rare blood cancer showed extremely promising results during a clinical trial.

In a study published in The New England Journal of Medicine, ibrutinib (Imbruvica) controlled Waldenstrom's Macroglobulinemia after 2 years in 95% of patients. The results showed the median overall response rate at 91% following a median 19 months of treatment.

Meanwhile, 69% of patients did not have their cancer worsen 2 years after starting treatment. When there was progression of the disease, it started at a median of 9.6 months following the onset of treatment.

Ibrutinib is the first and only treatment for the rare form of lymphoma, which affects approximately 1500 people in the United States each year.

"These findings herald a new era for the treatment of Waldenstrom's Macroglobulinemia, and show how genome sequencing can lead to the discovery of cancer mutations that can be specifically targeted by new therapies," first author Steven Treon, MD, PhD, said in a press release.

Waldenstrom's is caused by an abnormality in bone marrow B lymphocytes, which causes it to overproduce the immunoglobulin protein IgM that causes the blood to thicken. As a result, patients can suffer bleeding, dizziness, headaches, weight loss, bruising, and nerve damage.

Ibrutinib eliminates cancer cells by targeting a pathway that involves Bruton's tyrosine kinase protein.

The trial enrolled 63 patients who received at least 1 previous treatment taking daily ibrutinib orally until the disease worsened or unacceptable toxic effects began.

After taking ibrutinib, the median blood levels of IgM declined from 3520 mg per deciliter to 880 mg per deciliter. The median hemoglobin levels jumped from 10.5 g per deciliter to 13.8 g per deciliter.

Furthermore, bone marrow involvement dropped from 60% to 25%.

The highest response rates were reported in patients with the MYD88 genetic mutation without the CXCR4 mutation. The next highest response rate occurred in cancers with both the MYD88 and CXCR4 mutations, followed by patients who did not carry either mutation.

Adverse events from ibrutinib included low white blood cell and platelet counts, bleeding, and atrial fibrillation in patients with a history of arrhythmia.