Re-treatment with I-131 tositumomab in patients with non-Hodgkin's lymphoma who had previously responded to I-131 tositumomab.
OBJECTIVE
To study efficacy and safety of re-treatment with I-131 tositumomab in patients with low-grade, follicular, or transformed low-grade B-cell lymphoma who relapsed following a response to I-131 tositumomab.


METHODS
A prior response > or = 3 months to I-131 tositumomab was required. The single therapeutic dose following a dosimetric dose was adjusted to give the same total body dose (in Gy) as that used for the original dose, or was attenuated if the platelet count was less than 150,000 per mm(3) or if the prior treatment resulted in grade 4 cytopenias lasting longer than 7 days.


RESULTS
Of 32 patients enrolled, 28 completed the therapeutic dose. A median of four therapies were given before re-treatment. Eighteen (56%) of 32 patients had a complete or partial response (median duration, 15.2 months); eight (25%) had a complete response (median duration, 35 months). Five continue in response from 1.8 to 5.7 years, with a median follow-up of 35 months. The overall median response duration was not significantly different for the two treatments, with no clinical factors predicting response or its duration. Ten of 18 re-responders had longer responses with re-treatment, with five having responses > or = 1.5 years longer. Grade 3/4 neutropenia and thrombocytopenia occurred in 50% and 43% of patients, respectively, similar to initial treatment. Antimouse antibodies developed in 10% of patients, and 12% developed elevated serum thyroid-stimulating hormone. Six patients were diagnosed with second malignancies, including four patients who developed myelodysplastic syndrome (one who had not received the therapeutic dose) and one with acute myelogenous leukemia.


CONCLUSIONS
Re-treatment with I-131 tositumomab following a previous response can produce second responses that can be durable.
Kaminski
Mark S
MS
University of Michigan Comprehensive Cancer Center, Ann Arbor, USA. mkaminsk@umich.edu
Radford
John A
JA
Gregory
Stephanie A
SA
Leonard
John P
JP
Knox
Susan J
SJ
Kroll
Stewart
S
Wahl
Richard L
RL
D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D018951:Antigens, CD20 / Q000276:immunology; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D018796:Immunoconjugates / Q000627:therapeutic use; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D016393:Lymphoma, B-Cell / Q000276:immunology / Q000532:radiotherapy*; D008224:Lymphoma, Follicular / Q000532:radiotherapy; D008228:Lymphoma, Non-Hodgkin / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000532:radiotherapy; D016499:Radioimmunotherapy; D019233:Retreatment; D015996:Survival Rate; D016896:Treatment Outcome
D000911:Antibodies, Monoclonal; D018951:Antigens, CD20; D000970:Antineoplastic Agents; D018796:Immunoconjugates; D007457:Iodine Radioisotopes; C119496:tositumomab I-131