Background. One of the perspective therapeutic possibilities in follicular lymphomas (FL) is the fludarabine-based regimen FND (fludarabine, mitoxantron, dexamethason). However serious signs of myelotoxicity and significant immunosuppression with appearance of the opportunistic infections were described after the fludarabine treatment. Methods and Results. FoUicular lymphoma patients with advanced disease grade I-II were treated with FND (6-8 cycles). The immunotoxicity was evaluated by measuring of immunoglobuline levels (IgA, IgG, IgM) and that of lymphocytes subpopulations (CD3+, CD4+, CD8+, CD20+, CD56+) in peripheral blood. The myelotoxicity was evaluated by cultures of progenitor cells (CFC and LTC-IC). Totally 34 patients (medián age 55,5 years) were evaluated, the overall response was 72 % (CR 61 %, PR 11 %, progression 28 %). 73 % patients of 11 after 6-8 FND show persisting CR (27 % relapsed) with medián follow-up about 15 months. The dominating toxicity was myelotoxicity. The leucopenia grade III-IV occurred in about 30 % cycles. Because of toxicity it was necessary to reduce doses of FND in 10 % cycles and this treatment had to be finished ahead of schedule in 29 % patients. The significant immunotoxicity was found only in the decrease of whole lymphocyte population (p<0,05) and of IgG level (p<0,05). The decrease of lymphocyte subpopulations did not reach any statistical significance. The long-term myelotoxicity caused the decrease of LTC-IC that had a clinical correlation with the very difficult mobilization of PBSC. Conclusions. FND is efficient in treatment of follicular lymphoma. However myelotoxicity seems to be limiting. Myelotoxicity doesn't allow administering scheduled dose of FND in substantial amount of patients, long-term myelotoxicity complicates PBSC-mobilization. Lymphotoxicity is apparent, but seems not to be clinically important

        Key words: follicular lymphoma, fludarabine, myelotoxicity, immunotoxicity