Efficacy of 90Y-Ibritumomab Tiuxetan in Marginal-Zone Lymphoma (MZL).

Radio-immunotherapy (RIT) is an effective approach for patients with relapse-refractory NHL. RIT targets radiation to the tumor bulk while limiting exposure of normal tissues. Toxicity is prevalently hematologic, but transient and reversible. 90Y-Ibritumomab Tiuxetan in particular has demonstrated activity in follicular (FL) and Diffuse Large B-Cell (DLBC) NHL, but data are still lacking in MZL. 90Y-Ibritumomab Tiuxetan could offer an alternative option to those pts who relapse or do not respond to conventional treatment. We report efficacy results of a pilot study of 90Y-Ibritumomab Tiuxetan delivered at conventional activity (0,4 mCi/kg) in MZL patients. From May 2004 to July 2007, 15 patients were enrolled. Median age was 57 ys (range 36–83 ys); 9 female and 6 male. Six out of 15 pts had Helicobacter Pylori-negative gastric MALT (mucosa-associated lymphoid tissue) NHL. The remaining 9 pts had non gastric extranodal MZL. At time of treatment 6/15 pts had limited disease (stage I/II), 9/15 disseminated disease (stage III/IV; Ann-Arbor Staging System); bone marrow biopsy showed disease localization in 3/15 pts. Median number of previous therapies received was 2 (0–4): all pts except one had received prior CT, 7 prior Rituximab, 3 prior RT. Toxicities were primarily haematological, as expected, and reversible. Response evaluation was performed two months after 90Y-Ibritumomab Tiuxetan administration by upper gastrointestinal endoscopy with multiple biopsy and endoscopic ultrasonography in gastric NHL and by CT scan in the remaining pts. Ten out of 15 patients are now evaluable for response: 6 CR, 1 uCR, 3 SD. Response are durable: 5 CRs have been maintained for CR at 33, 26, 22, 15 and 14 months, respectively.

CONCLUSIONS: 90Y-Ibritumomab Tiuxetan seems to be very active in pts with MZL resistant or refractory to conventional systemic treatment. Its mechanism of action mimics conventional RT already known as valid option in MZL with localized disease. If these preliminary results are confirmed in larger number of patients, one single administration of 90Y-Ibritumomab Tiuxetan delivered at conventional activity (0,4 mCi/kg) could be considered a possible alternative option in the treatment of such indolent disease.