Iodine-131 tositumomab (Bexxar ®)
Tositumomab, commonly known as Bexxar ®, is a treatment being tested in people with certain types of non-Hodgkin lymphoma.
Here we aim to give a balanced summary of the information available so far, and this information should ideally be read with our general information about non-Hodgkin lymphoma.
You'll see your doctor regularly while you have this treatment so they can monitor its effects. This information should help you discuss any queries about your treatment and its side effects with your doctor or specialist nurse.
When a drug is being developed, it has to go through various stages of research called clinical trials or studies. These aim to establish:
- a safe dosage
- the side effects that the drug may cause
- which cancers it may be used to treat.
The trials also find out:
- how effective the drug is
- whether it's better than existing treatments
- whether it has extra benefits when given with existing drugs.
At the moment, Bexxar is only available to a small number of people in the UK, usually in clinical trials. In certain circumstances, it may also be given to individual patients who have been selected by their doctor as suitable - this is called a named-patient basis.
Many drugs that are thought to be promising may be found to not be as good as existing treatments, or to have side effects that outweigh any benefits. For this reason, doctors and other medical staff carry out frequent and careful checks on the progress of each patient who is having one of these developmental drugs. If you're taking a developmental drug, your doctor will tell you all about the drug, the procedures being used and how you'll be looked after while you're taking it. If at any time you have concerns, you should ask your doctor or nurse for information and advice.
Bexxar can only be given in hospitals with the appropriate specialist facilities, so you may need to travel to another hospital to receive it.
Bexxar belongs to a group of cancer drugs known as monoclonal antibodies. Monoclonal antibodies are sometimes called targeted therapies because they work by ‘targeting’ specific proteins (receptors) on the surface of cells.
Bexxar is a type of monoclonal antibody known as a radiolabelled monoclonal antibody. It is made up of a monoclonal antibody (tositumomab) with a radioactive substance attached to it (Iodine-131 or I-131). The radiation from I-131 can destroy cancer cells. It can also affect normal cells.
Bexxar ‘locks on’ to a protein called CD20, which is found on the surface of white blood cells called B-lymphocytes (B-cells). CD20 is present both on normal B-cells and on the abnormal (malignant) B-cells found in many types of non-Hodgkin lymphoma.
When Bexxar locks on to the B-cells, it delivers radiation that damages or kills them. Both normal and abnormal B-cells are killed, but the body can replace the normal B-cells that are damaged.
At the moment, Bexxar is only used in clinical trials to treat certain types of B-cell non-Hodgkin lymphoma that have come back after previous treatment.
Bexxar is given as a drip into a vein (intravenous infusion). It's usually given in the nuclear medicine department of the hospital.
You'll usually need to make four visits to the hospital over 1-2 weeks. The first three visits (between days one and seven) are needed to calculate how much radioactivity you will be given. On the fourth visit (between days seven and 14) you will be given the treatment dose of Bexxar. Before you start treatment, and for two weeks after it is finished, you'll need to take a daily iodine supplement. This is taken as tablets or liquid drops, and it helps protect the thyroid gland from the radioactive iodine.
On the first visit, you'll be given two infusions. The first is an infusion of the monoclonal antibody tositumomab, which is given over an hour. The second infusion contains tositumomab with a very small amount of radioactive iodine (I-131) and takes about 20 minutes to give. You'll then have a body scan. This takes about 15-30 minutes.
On your second and third visits, you'll have two more body scans. These show how the radiation has spread around your body. This helps the doctors calculate exactly how much radioactive iodine (I-131) to add to your treatment dose of Bexxar.
On the fourth visit you'll be given the actual treatment - called the therapeutic dose. You'll have two infusions. The first one is of tositumomab and is given over an hour. The second infusion is of tositumomab with the treatment dose of radioactive iodine (I-131). This is given over 20 minutes. You’ll be given steroids and an antihistamine drug to help prevent you having a reaction to the treatment. These are given through a drip.
You'll need to stay in hospital for a few days after this treatment because of the possibility of radiation exposure to other people. The risk to other people is small and most of the radiation will leave your body in your sweat and urine within a week.
Certain restrictions will be needed during this time. You will probably be looked after in a room of your own or with someone else having similar treatment. Lead screens will be placed at either side of your bed to absorb any radiation that leaves your body. Visiting times will be restricted, and pregnant women and children will not be allowed to visit. However, you should feel well and can bring books and magazines into your room, watch TV or listen to the radio to help pass the time.
Bexxar is still a relatively new drug so it's too early to know about all of the possible side effects. Those listed here appear to be the most common. If you notice any effects that aren't listed here, discuss them with your doctor or specialist nurse.
The treatment doesn't usually cause many problems. However, it is possible to have an allergic reaction to the monoclonal antibody in Bexxar. Signs of an allergic reaction include a skin rash, itching, swelling of the tongue or throat, irritation of the nasal passages, wheezing, a cough and breathlessness. You'll be monitored closely during your treatment, but tell a nurse or doctor if you have any of these symptoms.
To reduce the chance of developing an allergic reaction, you'll be given medicines such as antihistamines before the infusion. If a reaction does occur, the Bexxar infusion can be slowed down or stopped until the reaction is over.
These may include fever, chills, sweating, headaches, itching, and joint and muscle aches. These effects may occur a few hours after the drug is given, but they don't usually last for more than a day or two.
Feeling sick (nausea), being sick (vomiting) and tummy (abdominal) pain
Occasionally, some people have these effects in the first few days after the treatment. Let your nurse or doctor know if you feel sick or have tummy pain, as they can prescribe medicines to help.
Diarrhoea may occur a few days after treatment. It can usually be controlled with medicine, but let your doctor know if it’s severe or continues. It's important to drink plenty of fluids if you have diarrhoea.
Risk of infection
Bexxar can reduce the number of white blood cells in your blood, which help to fight infection. White blood cells are produced by the bone marrow. If the number of white blood cells is low, you will be more prone to prone to infections. A low white blood cell count is called neutropenia. Your resistance to infection usually reaches its lowest point 4-7 weeks after the first dose of Bexxar and remains low for about a month. Your white blood cell levels then increase steadily and usually return to normal over several weeks.
Contact your doctor or the hospital straight away if:
- your temperature goes above 38˚C (100.4˚F)
- you suddenly feel unwell, even if your temperature is normal.
You'll have regular blood tests to check your blood cell count.
Bruising or bleeding
Bexxar can reduce the production of platelets, which help the blood to clot. Tell your doctor if you have any unexplained bruising or bleeding, such as nosebleeds, bleeding gums, blood spots or rashes on the skin. You can have a platelet transfusion if your platelet count is low.
Anaemia (low number of red blood cells)
Bexxar can reduce the number of red blood cells, which carry oxygen around the body. A low red cell count is called anaemia. This may make you feel tired and breathless. Tell your doctor or nurse if you have these symptoms. You may need to have a blood transfusion if the number of red blood cells becomes too low. Red blood cell numbers usually recover in 3-4 weeks.
Bexxar can affect the thyroid gland in some people, making it work less effectively. Symptoms of an underactive thyroid may include tiredness, weight gain, constipation, aches, feeling cold, dry skin and dry hair. You will have a yearly blood test to check your thyroid gland is working normally and, if needed, you can be given thyroid hormone tablets.
There is a risk that Bexxar may cause a second cancer to develop. Your doctor should discuss this risk with you.
It’s important to let your doctor know straight away if you feel unwell or have any severe side effects, even if they’re not mentioned above.
Bexxar makes you slightly radioactive for a few days after your treatment. You may still have a very small amount of radiation in your body when you go home, but it will disappear over the next few days. Your doctor or nurse will advise you about any precautions you need to take at this time.
You may be advised to stay up to two metres (six feet) away from others, particularly children, for a few days. What precautions you need to take and for how long will depend on the dose of radiation you're given. They may also vary according to hospital guidelines.
Some medicines should only be used under the supervision of your doctor while you have Bexxar treatment. This includes blood thinners (anticoagulants) and drugs such as aspirin and ibuprofen.
Some other medicines, including those you can buy in a shop or chemist, can be harmful to take when you’re having Bexxar. Tell your doctor about any medicines you are taking, including over-the-counter drugs, complementary therapies and herbal drugs.
Your ability to become pregnant or father a child may be affected by having this treatment. It's important to discuss fertility with your doctor before starting treatment.
It's not advisable to become pregnant or father a child during treatment with Bexxar, or for one year afterwards. This is because it may harm the developing baby. It's important to use effective contraception during treatment. You can discuss this with your doctor.
There is a potential risk that Bexxar may be present in breast milk so women are advised not to breastfeed during treatment and for a few months afterwards.
If you are travelling by air it's possible you could set off radiation detectors at airports for some weeks after treatment with Bexxar. You may be questioned by security staff, so it's a good idea to have a doctor's letter that explains that you have recently had radioactive iodine treatment.
Non-cancer hospital admission
If you’re admitted to hospital for a reason not related to the cancer, it’s important to tell the doctors and nurses looking after you that you are having Bexxar treatment. You should tell them the name of your cancer specialist so that they can ask them for advice.
It’s a good idea to know who you should contact if you have any problems or troublesome side effects when you’re at home. During office hours you can contact the clinic or ward where you had your treatment. Your specialist nurse or doctor will tell you who to contact during the evening or at weekends.
This information has been compiled using a number of reliable sources, including:
- GlaxoSmithKline. Prescribing information Bexxar® (Tositumomab and Iodine I 131 Tositumomab). 2005.
- Chamarthy M. R, et al. Radioimmunotherapy of Non-Hodgkin’s Lymphoma: From the ‘Magic Bullets’ to ‘Radioactive Magic Bullets’. Yale Journal of Biology and Medicine. 2011. 84(4): 391-407.
With thanks to Dr Andrew Davies, Senior Lecturer in Medical Oncology and Honorary Consultant, and the people affected by cancer who reviewed this edition. Reviewing information is just one of the ways you could help when you join our Cancer Voices network.