Evaluating the long-term effectiveness of ibrutinib–rituximab treatment versus standard chemoimmunotherapy in patients with chronic lymphocytic leukemia.

This study investigated the long-term effectiveness of ibrutinib (Imbruvica)–rituximab (Rituxan) (IR) treatment versus standard chemoimmunotherapy (CIT) in patients aged 70 or younger with previously untreated chronic lymphocytic leukemia (CLL). The data showed that the IT regimen significantly improved the survival outcomes compared to standard CIT over the long term in these patients.

Chronic lymphocytic leukemia (CLL) is a type of cancer in which the bone marrow makes too many lymphocytes (a type of white blood cell). Highly effective targeted therapies have been developed for CLL as it can be challenging to treat.

Standard CIT for CLL consists of fludarabine (Fludara), cyclophosphamide (Cytoxan), and rituximab (FCR regimen). Ibrutinib is a targeted therapy known as a kinase inhibitor. It has shown good outcomes when given alone and has been approved for the treatment of CLL. Rituximab is an immune protein that works by helping the body’s immune system attack cancer cells. The combination of ibrutinib and rituximab has been used in trials for the treatment of CLL. However, the long-term effectiveness and safety of ibrutinib–rituximab (IR) treatment versus standard CIT in patients with CLL are still unknown.

This study involved 529 patients aged 70 or younger with previously untreated CLL. Patients were randomly assigned into 2 groups. Group 1 included 354 patients who received IR for six cycles, followed by ibrutinib until disease progression. Group 2 included 175 patients who received six cycles of CIT (FCR regimen). The average follow-up time was 5.8 years.

Patients in group 1 were 73% more likely to survive without cancer worsening compared to patients in group 2. 

Among the 354 patients who received the IR regimen, 214 (60.5%) patients remained on ibrutinib. Among the 138 patients who stopped treatment, 37 (10.5%) patients stopped therapy due to disease progression or death, 77 (21.9%) patients stopped therapy for side effects, and 24 (6.8%) patients withdrew for other reasons. Disease progression was uncommon among patients able to remain on ibrutinib.

Among patients in group 1, the average survival from stopping treatment until disease progression or death was 25 months for patients who stopped treatment for a reason other than disease progression. Patients in group 1 were 53% more likely to have a better overall survival compared to patients in group 2.

This study concluded that the ibrutinib–rituximab regimen significantly improved the survival outcomes compared to standard CIT over the long term in patients aged 70 or younger with previously untreated CLL.

This study was sponsored by Pharmacyclics, the manufacturer of ibrutinib.