10000 Background: Pediatric mature B-cell NHL differ from aggressive B-NHL of adults in terms of biology and treatment outcome. In contrast to adults, rituximab (Rx) is not established in the treatment of pediatric B-NHL has not be determined yet. Even the activity of Rx in pediatric B-NHL is not determined. We conducted a phase II window study to examine the activity of Rx in newly diagnosed pediatric B-NHL.

METHODS: Eligibility: age < 19 y, CD20 B-NHL, ≥ 1 measurable lesion/s, informed consent. Exclusion: Lansky performance scale 5, pre-treatment, impaired renal-, heart-, liver-function, hepatitis B, pre-existing disease, pregnancy.

RESULTS: One hundred thirty-six pts were enrolled from 04/04-08/08. NTC °3/4 toxicities: general condition 16%, fatigue 13%, anaphylaxis (chill/fever/bronchospasm) 6 (1/2/4)%, infection 3%, S-GOT/GPT 10%, acute tumor lysis (ATL) 7%, capillary leakage (0), toxic death (0). Forty-nine pts were not evaluable for response: Withdrawal (anaphylaxis 8, ATL 2, suspected progression, not verified 4, other 2), IT therapy in CNS- pts (8), corticosteroids (3), technical inadequacy of response evaluation (21), no index lesion (1). Of the 87 evaluable pts 37 were RPs (42.5%, 95%-CI 32% - 54%). RR by histology: BL/B-ALL 29/68, DLBCL 6/14, juvenile follicular lymphoma 1/2, PMBCL 1/1, B-NHL nfs 0/2. Fifty pts were non-RPs.

CONCLUSIONS: Although the RR was lower than requested Rx as single agent is active in pediatric B-NHL. No significant financial relationships to disclose.

CONCLUSION: As shown by the significant influence of metastatic sites, some P die from their advanced systemic disease situation before they would experience cerebral progression, in part explaining the influence of systemic treatment. In other individuals however, intensified local treatment and systemic treatment appear to influence both cTTP and OS significantly, implicating a direct influence of systemic therapy on BM. This might result from an impaired blood brain barrier around metastatic sites, making sufficient tissue concentrations of cytotoxic agents possible. No significant financial relationships to disclose.

TREATMENT: Rx 375 mg/m(2) IV at day 1; concomitant therapy: Rasburicase, steroids only for anaphylaxis, intrathecal (IT) triple drug at days 1, 3 for CNS pts only. Begin of chemotherapy at day 5. Response evaluation: product of 2 perpendicular diameters of 1 - 3 index lesions/% blasts in BM/PB within 24 h prior to Rx and at day 5: responder (RP): at least 1 lesion with at least objective effect (decrease of ≥25%) and no progress (increase of ≥25 %) at other sites. Study plan: Simon 2-stage phase II with α and β = 5%. Response rate (RR) for poor activity was set to 45%, for good activity 65%. 33 pts entered the first stage, final evaluation after 79 pts.