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Prolonged Rituximab Treatment Improves Event-Free Survival and Response Duration in Follicular Lymphoma: Presented at ASH

By Bruce Sylvester

PHILADELPHIA, PA -- December 12, 2002 -- The anti-tumor effect of rituximab continues long after the end of its therapeutic administration, researchers report, according to research presented at the annual meeting of the American Society of Hematology held here December 6-10.

Previous research showed that the efficacy of rituximab increased with duration of treatment, said Michele Ghielmini, MD, clinical researcher with the Lymphoma Working Group, Swiss Group for Clinical Cancer Research (SAKK) in Bern, Switzerland. "We wanted to compare the effects of a standard course of therapy with a prolonged course to study and verify this clinical phenomena," he added.

His team enrolled 202 patients with newly diagnosed or resistant/relapsed follicular lymphoma who received standard induction treatment with rituximab 375 mg/m² weekly for four weeks.

Subjects who responded or had stable disease at week 12 were randomized to observation or maintenance therapy with rituximab 375 mg/m² every eight weeks at months 3, 5, 7 and 9.

The 185 evaluable patients responded to induction therapy at a rate of 46 percent for pretreated patients and 67 percent for chemotherapy-naive patients (p<0.01).

"Adverse predictors of response were bulky disease (p=0.002) and male gender (p=0.04)," the researchers noted.

A total of 151 subjects were randomized to observation versus maintenance therapy. Patient characteristics were equally balanced between both arms, according to the authors.

The median event-free survival (EFS) at a median follow-up of 35 months from the start of induction treatment was 12 months for the observation arm and 23 months for the maintenance arm (p=0.02). The difference was more pronounced in chemotherapy-naive patients (19 versus 36 months, p=0.009). Dr. Ghielmini noted.

Among subjects in the observation arm who showed a treatment response at week 12, 56 percent were still in remission at 12 months compared to 80 percent in the maintenance arm (p=0.01).

Median duration of response was 17 months for the observation arm compared to 36 months for the maintenance arm (p=0.0009).

At the end of induction treatment, 34 patients achieved improved responses, and the rate of complete response increased from 10 percent at randomization to 16 percent at month 7, 23 percent at month 12, and 29 percent at further follow-up. There was no difference in complete response rate between the two arms, the investigators reported.

"The number of circulating B-lymphocytes tended to return to pre-treatment levels after one year of observation (65 percent of baseline), while they remained low in patients receiving prolonged treatment (33 percent of baseline, p=0.04). Plasma levels of immunoglobulin (Ig) G, IgA and IgM remained stable for both groups, and incidence of infections and other side effects was also low.

According to the researchers, the findings show that patients with follicular lymphoma who are stable or respond to standard rituximab treatment benefit from treatment with additional 4 single doses of rituximab at two-month intervals, achieving reduced risk of progression or relapse as well as a significantly improved chance of remaining in remission at one year, without inducing additional toxicity.

"This effect is obtained mainly by the capacity of maintenance treatment to prevent relapse in responding patients," the authors concluded.

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