Tolerance of Treatment Subsequent to Front-Line Tositumomab/Iodine-131 Tositumomab in Patients With Follicular Lymphoma

Front-line treatment for previously untreated follicular B-cell lymphoma with the iodine-131-labeled anti-CD20 antibody tositumomab (Bexxar) has been reported to result in a 97% response rate and a 74% complete response rate. Although the median duration of response has not yet been reached with a median follow-up of 2.7 years, concerns have been raised over the tolerability of salvage treatments upon relapse of disease. We have reviewed the clinical course of the 28 patients that have relapsed among the original group of 76 patients treated with tositumomab/iodine-131 tositumomab as front-line therapy.

Of 28 relapsed patients (median age, 50 years [range: 28-60 years]), 22 have received some form of treatment and 6 are being observed. For those who were subsequently treated, the median time from tositumomab/iodine-131 tositumomab treatment to salvage treatment was 321 days (range: 67-1,440 days) and the median time from relapse to treatment was 104 days (range: 3-775 days). Seventeen patients received at least one chemotherapy regimen at some point, 12 received rituximab(Drug information on rituximab) (Rituxan) either alone or in combination with chemotherapy, 8 received localized irradiation (one as the only subsequent treatment), and 1 was retreated with tositumomab/iodine-131 tositumomab. The median number of total regimens received post-tositumomab/iodine-131 tositumomab was 2.5 (range: 1-7).

Of the 17 patients who received chemotherapy, 8 were given 2 or more regimens (range: 2-5), including 4 patients who underwent stem cell transplants (2 autologous, 2 allogeneic). All four of these transplanted patients had received at least three prior chemotherapy regimens. With only one exception, no patient had treatment discontinued because of blood count intolerance due to a hypocellular marrow. No difficulties were encountered in stem cell mobilization or engraftment posttransplant. No cases of myelodysplasia or acute myelogenous leukemia have been observed to date. There were no adverse effects beyond those expected in patients treated with rituximab or local irradiation.

CONCLUSION: Front-line tositumomab/iodine-131 tositumomab therapy does not preclude other treatment options, including those involving myelosuppressive agents.