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regimen-monograph
TOSI
A - Regimen Name
TOSI Regimen
Tositumomab
Disease Site
Hematologic - Lymphoma - Non-Hodgkin's Low Grade
Intent
Palliative
Regimen Category
Standard : Standard therapy endorsed by the Disease Site Group or a regimen widely used by most Regional Cancer Centres in this disease site. The category is unrelated to the source or availability of funding.
Rationale and Uses
Patients with CD20 positive follicular non-Hodgkin’s lymphomas who are refractory to chemotherapy and rituximab, and those with transformed non-Hodgkin’s lymphoma that is refractory to at least one prior course of chemotherapy, with or without rituximab.
B - Drug Regimen
| tositumomab | See Table | ||||||||||||||||||||||||||||||||
* Doses should be modified in the presence of thrombocytopenia (100 to <150 x 109/L).
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D - Premedication and Supportive Measures
Antiemetic Regimen:
Minimal
Other Supportive Care:
- Thyroid Protection Regimen:
- Saturated solution of potassium iodide (SSKI) 4 drops PO three times daily OR
- Lugol’s solution 20 drops PO three times daily OR
- Potassium iodide tablets 130mg PO daily
- Administered at least 24 hours (i.e. at least 3 doses of SSKI OR 3 doses of Lugol’s solution, OR at least one dose of 130mg KI tablet administered) prior to the administration of the 131I-tositumomab dosimetric dose and continued until 2 weeks after administration of the 131I-tositumomab therapeutic dose.
- Premedication for administration of tositumomab in the dosimetric and therapeutic steps (30 min prior):
- Acetaminophen 650mg po
- Diphenhydramine 50mg po
E - Dose Modifications
Doses should be modified according to the protocol by which the patient is being treated. The following recommendations have been adapted from clinical trials or product monographs and could be considered.
Dosage with toxicity
Hematologic Toxicities:
Doses should be modified in the presence of thrombocytopenia (100 to < 150 x 109/L); 131I tositumomab should not be given to patients with platelet count less than 100 x 109/L. Also do not administer if patient has ANC < 1.5 x 109/L, impaired bone marrow reserve, prior myeloablative therapy with stem cell support, or bone marrow involvement greater than 25%.
Dose modification for other toxicity:
Tositumomab and 131I-tositumomab should be permanently discontinued in patients who develop severe hypersensitivity reactions.
Hepatic Impairment
No data available
Renal Impairment
No data available; however the kidneys are the main route of excretion of 131I–tositumomab, and reduced clearance may result in increased radioactivity exposure.
F - Adverse Effects
Refer to tositumomab drug monograph(s) for additional details of adverse effects
Most Common Side Effects |
Less Common Side Effects, but may be |
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H - Drug Administration and Special Precautions
Refer to tositumomab drug monograph(s) for additional details
I - Recommended Clinical Monitoring
Recommended Clinical Monitoring
- Complete blood count (CBC) with differential; prior to and weekly following administration of tositumomab and 131I-tositumomab until levels recover; monitoring should be more frequent in patients who develop moderate or severe cytopenia, or as clinically indicated.
- Liver function tests; baseline
- Monitor all patients closely, especially those with pre-existing cardiac and pulmonary conditions or prior significant cardiac adverse events.
- Patients who have had prior exposure to murine proteins should be screened for HAMA as they may be at increased risk for hypersensitivity; prior to treatment
- Renal function tests; baseline and prior to treatment
- TSH and/or signs or symptoms of hypothyroidism at baseline, every 6 months for the first 2 years, and annually thereafter
- Vital signs and signs and symptoms of infusion-related or allergic reactions to be monitored during each of the infusions. Watch for signs and symptoms for up to 48 hours after the infusion.
- Clinical assessment of bleeding, infection and GI effects
- Grade toxicity using the current NCI-CTCAE (Common Terminology Criteria for Adverse Events) version
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J - Administrative Information
Tositumomab and 131I -tositumomab (Bexxar® regimen) is a complex radioisotope-containing regimen and should only be administered in specialized units by authorized personnel.
K - References
Davis T, Kaminski MS, Leonard JP, et al. Long-term results of a randomized trial compared tositumomab and Iodine-131 tositumomab (Bexxar) with tositumomab alone in patients with relapsed or refractory low-grade or transformed low grade or transformed low grade NHL [abstract] Blood 2003;102 (11 Pt 1):405a, A1474.
Davies AJ, Rohatiner AZ, Howell S, et al., Tositumomab and iodine I 131 tositumomab for recurrent indolent and transformed B cell NHL. J Clin Oncol 2004;22(8):1469-79.
Kaminski MS, Zelenetz AD, Press OW, et al., Pivotal study of iodine I 131 tositumomab for chemotherapy-refractory low grade or transformed low grade B cell NHL, J Clin Oncol 2001;19(19):3918-28.
Horning SJ, Younes A, Jain V, Kroll S et al., Efficacy and safety of tositumomab and iodine 131 tositumomab in B cell lymphoma, progressive after rituximab. J Clin Oncol 2005; 23(4):712-9.
October 2017 Removed archived PEBC link
M - Disclaimer
Regimen Abstracts
A Regimen Abstract is an abbreviated version of a Regimen Monograph and contains only top level information on usage, dosing, schedule, cycle length and special notes (if available). It is intended for healthcare providers and is to be used for informational purposes only. It is not intended to constitute or be a substitute for medical advice, and all uses of the Regimen Abstract are subject to clinical judgment. Such information is provided on an “as-is” basis, without any representation, warranty, or condition, whether express, or implied, statutory or otherwise, as to the information’s quality, accuracy, currency, completeness, or reliability, and Cancer Care Ontario disclaims all liability for the use of this information, and for any claims, actions, demands or suits that arise from such use.
Information in regimen abstracts is accurate to the extent of the ST-QBP regimen master listings, and has not undergone the full review process of a regimen monograph. Full regimen monographs will be published for each ST-QBP regimen as they are developed.
Regimen Monographs
Refer to the New Drug Funding Program or Ontario Public Drug Programs websites for the most up-to-date public funding information.
The information set out in the drug monographs, regimen monographs, appendices and symptom management information (for health professionals) contained in the Drug Formulary (the "Formulary") is intended for healthcare providers and is to be used for informational purposes only. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects of a particular drug, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for a given condition. The information in the Formulary is not intended to constitute or be a substitute for medical advice and should not be relied upon in any such regard. All uses of the Formulary are subject to clinical judgment and actual prescribing patterns may not follow the information provided in the Formulary.
The format and content of the drug monographs, regimen monographs, appendices and symptom management information contained in the Formulary will change as they are reviewed and revised on a periodic basis. The date of last revision will be visible on each page of the monograph and regimen. Since standards of usage are constantly evolving, it is advised that the Formulary not be used as the sole source of information. It is strongly recommended that original references or product monograph be consulted prior to using a chemotherapy regimen for the first time.
Some Formulary documents, such as the medication information sheets, regimen information sheets and symptom management information (for patients), are intended for patients. Patients should always consult with their healthcare provider if they have questions regarding any information set out in the Formulary documents.
While care has been taken in the preparation of the information contained in the Formulary, such information is provided on an “as-is” basis, without any representation, warranty, or condition, whether express, or implied, statutory or otherwise, as to the information’s quality, accuracy, currency, completeness, or reliability.
CCO and the Formulary’s content providers shall have no liability, whether direct, indirect, consequential, contingent, special, or incidental, related to or arising from the information in the Formulary or its use thereof, whether based on breach of contract or tort (including negligence), and even if advised of the possibility thereof. Anyone using the information in the Formulary does so at his or her own risk, and by using such information, agrees to indemnify CCO and its content providers from any and all liability, loss, damages, costs and expenses (including legal fees and expenses) arising from such person’s use of the information in the Formulary.
Last Updated: July 27, 2026
