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Tositumomab and Iodine 131 I-Tositumomab

Pronunciation: TOE-sih-too-MOE-mab EYE-uh-dine
Class: Monoclonal antibody

Trade Names

Bexxar
- Injection kits

Bexxar therapy (Canada)

Pharmacology

Blocks (complement-dependent cytotoxicity) CD20 antigen, which is found on the surface of normal and malignant B lymphocytes. Cell death is associated with ionizing radiation from the radioisotope.

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Indications and Usage

Treatment of patients with CD20 positive, follicular, non-Hodgkin lymphoma, with and without transformation, whose disease is refractory to rituximab and has relapsed following chemotherapy.

Contraindications

Hypersensitivity to murine proteins or any component of the therapeutic regimen.

Dosage and Administration

Adults

IV The therapeutic regimen consists of 4 components administered in 2 discrete steps: the dosimetric step followed in 7 to 14 days by the therapeutic step.

Dosimetric step

IV Tositumomab 450 mg over 60 min. Reduce the rate 50% for mild to moderate infusional toxicity; interrupt infusion for severe infusional toxicity. After resolution of severe infusional toxicity, resume infusion at a 50% reduction in infusion rate. IV 131 I-tositumomab, which contains 5 mCi 131 I and 35 mg tositumomab, in 30 mL of 0.9% sodium chloride infused over 20 min. Reduce the rate 50% for mild to moderate infusional toxicity; interrupt infusion for severe infusional toxicity. After resolution of severe infusional toxicity, resume infusion at a 50% reduction in infusion rate.

Therapeutic step (7 to 14 days after dosimetric step; do not administer if biodistribution is altered)

IV Tositumomab 450 mg over 60 min. Reduce the rate by 50% for mild to moderate infusional toxicity; interrupt infusion for severe infusional toxicity. After resolution of severe infusional toxicity, resume infusion at a 50% reduction in infusion rate. IV 131 I-tositumomab, reduce the rate 50% for mild to moderate infusional toxicity; interrupt infusion for severe infusional toxicity. After resolution of severe infusional toxicity, resume infusion at a 50% reduction in rate.

Premedication
Adults

PO Thyroid protective agents: Saturated solution of potassium iodide (SSKI) 4 drops 3 times daily; Lugols solution 20 drops 3 times daily; or potassium iodide tablets 130 mg every day. Start thyroid protective agents at least 24 h prior to administration of 131 I-tositumomab dosimetric dose and continue until 2 wk after administration of the 131 I-tositumomab therapeutic dose. Ameliorate/prevent infusion reaction: Acetaminophen 650 mg and diphenhydramine 50 mg, 30 min prior to administration of tositumomab in the dosimetric and therapeutic steps.

General Advice

  • For IV administration only. Not for intradermal, SC, or IM administration.
  • Administer dosimetric and therapeutic dose through the same IV tubing set with in-line 0.22 micro filter. Changing IV tubing and filter between doses can result in loss of drug.

Storage/Stability

Store tositumomab in refrigerator (36° to 46°F) prior to dilution. Protect from strong light. Do not shake and do not freeze. Diluted solutions can be stored for up to 24 h in refrigerator or for up to 8 h at room temperature (59° to 86°F). Discard any unused portions in the vial. Store iodine 131 I-tositumomab in original lead pot in freezer (-4°F or below) prior to dilution. Diluted solution can be stored for up to 8 h in refrigerator or at room temperature.

Drug Interactions

None well documented.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Hypotension (7%); vasodilation (5%).

CNS

Headache (16%); dizziness, somnolence (5%).

Dermatologic

Rash (17%); pruritus (10%); sweating (8%).

EENT

Pharyngitis (12%); rhinitis (10%).

GI

Nausea (36%); abdominal pain, vomiting (15%); anorexia (14%); diarrhea (12%); constipation, dyspepsia (6%).

Hematologic

Hematologic toxicities (most frequently observed adverse event); hemorrhage in thrombocytopenic patients; secondary leukemia; myelodysplasia.

Metabolic

Peripheral edema (9%); weight loss (6%); dehydration.

Musculoskeletal

Myalgia (13%); arthralgia (10%).

Respiratory

Increased cough (21%); dyspnea (11%); pneumonia (6%)

Miscellaneous

Asthenia (46%); infection (eg, sepsis [45%]); fever (37%); pain (19%); chills (18%); hypothyroidism (14%); back pain (8%); chest pain (7%); neck pain, hypersensitivity (6%); severe and prolonged cytopenias; allergic reactions; infusional toxicity (including fever, rigors/chills, sweating); pleural effusion.

Precautions

Warnings

Hypersensitivity reactions

Medications for treatment of severe hypersensitivity, including anaphylaxis, should be available.

Cytopenias

Prolonged and severe thrombocytopenia and neutropenia may occur.

Pregnancy

Fetal harm can occur.

Special requirements

Only physicians and other health care professionals qualified by training in the safe use and handling of therapeutic radionuclides should administer 131 I-tositumomab.


Pregnancy

Category X .

Lactation

Excreted in breast milk.

Children

Safety and efficacy not established.

Elderly

Rate and duration of response were decreased in patients 65 yr and older.

Hypersensitivity

Hypersensitivity reactions, including anaphylaxis, may occur.

Renal Function

Impaired renal function may decrease rate of excretion of radiolabeled iodine, increasing exposure to the radioactive component.

Carcinogenesis

Radiation is a potential carcinogen.

Malignancies

Myelodysplastic syndrome and/or acute leukemia may occur.

Hypothyroidism

May occur. All patients must receive thyroid blocking agents.

Overdosage

Symptoms

Hematologic toxicity.

Patient Information

  • Advise patient, family, or caregiver that medication will be prepared and administered in a health care setting by a health care provider.
  • Reinforce need for compliance with thyroid blocking agents and life-long monitoring of thyroid function.
  • Advise patient of the risks associated with cytopenias and the need for frequent monitoring of blood counts for up to 12 wk after treatment and possibly longer.
  • Advise patient that radioactive material will be in the body for several days following each dose. Provide and review with patient, family, or caregiver written instructions for minimizing radiation exposure of family members, friends, and the general public.
  • Advise patient to immediately report any of the following to health care provider: fever or other signs of infection, sore throat, bleeding, unusual bruising or small purple spots under the skin, signs of an allergic reaction (eg, shortness of breath, rash, hives).
  • Instruct women of childbearing potential to use effective contraception before starting treatment, during therapy, and for 12 mo after therapy has been completed.
  • Instruct sexually active men to use effective contraception during therapy and for 12 mo after therapy has been completed.

Copyright © 2009 Wolters Kluwer Health.

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