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Your doctor has recommended a medication called Herceptin as treatment for your breast cancer. This information sheet provides a brief introduction to Herceptin and explains the common side effects you may experience. This does not mean you will definitely get them. It is also possible you may experience a side effect not mentioned here.
What is Herceptin?
It is not chemotherapy or a
hormone therapy. It is called a monoclonal antibody which utilises
the natural immune system to kill tumour cells. Although cancers grow
mainly beyond normal growth control,
they are sufficiently similar to the own 
body’s
cells to enable them to hide from the immune system (the body’s defence mechanism against “foreign”
attack). There are, however, some subtle differences between cancer cells
and normal cells. Some of these differences may be detected with special
sensitive laboratory tests. In the case of breast cancer there may be too many
copies of a cancer-causing gene called an oncogene. This oncogene called HER2 is
part of a family of genes called c-erbB-2 (otherwise known as her-2-/neu). Each HER2 gene results in the
expression of a receptor on the surface of the cell. If the gene makes too much
receptor, it is referred to as being "over expressed".
Cells that over express too much of the HER2 gene can be a specific
target for therapies such as Herceptin. Technology now exists to make antibodies
in the laboratory called monoclonal antibodies. Specific antibodies have been
made to detect and attach to the HER2 receptors. The antibody is therefore known
as anti-HER2 called trastuzumab or its commercial name
Herceptin.
How does Herceptin work? Herceptin works in a different way than standard cancer therapy, such as chemotherapy or hormone therapies. Herceptin® (Trastuzumab) is believed to function in three main ways:
1) Blocking tumour cell growth: Herceptin binds to the HER2 (receptors) on the tumour cell surface and this stops the receptor signalling the cell to grow and divide.
2) Signalling of the immune system: Certain immune system cells, called natural killer (NK) cells, attach to Herceptin when it is bound to the tumour cells. The NK cells then detect an abnormality, and kill the tumour cell.
3) Working with chemotherapy: Herceptin and chemotherapy work in different ways, but when given together, the two drugs can form a partnership (synergy) so kill tumour cells more effectively than either Herceptin or chemotherapy when given alone.
Who is eligible for Herceptin? Patients must have tumours which over express the HER2 protein (see above). Herceptin is currently approved for use in patients whose cancer has spread from the breast to other sites (metastasised). It is usually given in combination with chemotherapy drugs called taxanes. It is sometimes given with other chemotherapy drugs at the discretion of the oncologist but these combinations have not yet gained regulatory approval. Herceptin can also be given on its own (monotherapy) if patients have received a taxane or anthracycline containing chemotherapy regimens previously (or cannot tolerate these drugs). For these indications the aim of treatment is not to cure, but to control specific symptoms caused by the cancer. This is otherwise known as palliative treatment. It is hoped that treatment improves the quality of life; therefore the side effects from the treatment should not outweigh the benefits of shrinking the tumour.
There is now emerging evidence that Herceptin is likely to have a benefit after the initial diagnosis of HER2+ve breast cancer (adjuvant). These trials are very new and regulatory bodies have not yet given their approval.
Preparation for Herceptin. As Herceptin is a very specific treatment, your 
doctor
needs to find out if your tumour over-expresses
HER-2
receptors before even considering treatment. This is usually achieved by
performing a special laboratory test on a small piece of you original tumour
(from the time of your original surgery or biopsy). Occasionally, your doctor
may need a more recent tumour for analysis and may recommend a further biopsy.
In either case the tumour is usually send to a lab which specialises in specific
tests called immunohistochemistry. A report will be issued by the pathologist on
whether your tumour over expresses HER2 and how much is expressed. Research
has shown that 20-25% of women have tumours which do over express HER2. If the cancer does over express HER2 it will look
brown/red down the microscope (see 1st left picture). Pathologists
have a
scale of 0-3 depending on the intensity of staining, if it 1 or 0 it is regarded
as HER-2 negative and Herceptin should not be used as treatment If it is grade 2
then a more sensitive test called FISH is performed, which looks at the DNA
of the tumour cells (second left picture). All tumours which are FISH positive or have 3+ intensity
staining on immunohistochemistry are eligible for Herceptin.
How is Herceptin administered? Herceptin cannot be taken orally as it would be
destroyed by your stomach. It is, therefore, given as a drip into a vein usually
over 90 minutes followed by a period of observation. Occasionally, it is possible to
get
an allergic reaction, particularly to the first treatment. The nurses will therefore be checking "how you are
feeling" and measuring your breathing, pulse and blood pressure blood
regularly. If all 
goes well the drip can last 1-2 hours,
but sometimes, in
response to mild reaction, it may have to be slowed down over several hours.
Rarely if the allergic reaction is prominent it has to be stopped altogether
and abandoned. To avoid a mild reaction often paracetamol and an antihistamine
are given before the infusion. The dose is calculated by the weight of the patient,
this is most often 4mg/kg on the first day then 2mg/kg once a week. This
treatment continues until
the tumour stops responding. However, based on recent information your doctor
may choose to give Herceptin every three weeks particularly if this coincides with the
chemotherapy visits. Herceptin is usually
given within a cancer department
or hospital. In some areas of the country, after the first few treatments it may be possible to
receive the
Herceptin infusion in your own home provided these facilities have been set up
and are available
locally. As mentioned above, Herceptin may also be given in conjunction with chemotherapy.
The dose, frequency of treatment and
side effects will also depend on the chemotherapy drugs used. The rationale and the specific regimen will be explained to
you by the doctors and nurses before therapy starts.
Are there any side effects to Herceptin? When given with chemotherapy most of the side effects relate to the chemotherapy drugs (see chemotherapy). Herceptin generally does not make these worse. Herceptin does have some mild side effects on its own which may occur in addition to those caused by chemotherapy. As mentioned above this does not mean you will definitely get them. It is also possible you may experience a side effect not mentioned here:-
The early effects often are related to an "allergic" reaction. If they do occur, it is often while the drug is being infused or shortly afterwards.
Potential side effects include:
If associated with a fast pulse and lower blood pressure these symptoms indicate an early allergic reaction. As mentioned above if these symptoms are prominent the infusion has to be slowed down or abandoned altogether. To avoid a mild reaction often paracetamol and an antihistamine are given before the infusion.
The ongoing effects may occur at any time whilst you are receiving Herceptin. These are usually worse a day or two after the infusion and could include:-
Late side effects may occur after receiving Herceptin for some time. The most important of these is heart damage - this is rare (In clinical trials around 4%). To ensure patients receiving Herceptin do not experience any damage to the heart, all patients must have a test for heart function before starting treatment and at regular intervals (usually every few months) after starting Herceptin. These tests include an echocardiogram or MUGA scan. The risks of the development of heart damage are higher if you have previously received chemotherapy containing drugs called anthracyclines or if you already have an underlying heart or lung problem.
How will I know the treatment is working? Your doctor would require evidence that treatment is helping particularly after a 2-3 months. This can be achieved from a number of sources including; an improvement in a specific symptom such as pain, a shrinkage of a lump on examination, improvements in a blood test or often evidence from repeat X-rays and scans such as CT or MRI. If there is no palliative benefit by this time treatment may be stopped.
Further general information Your doctors and specialist nurses are in an ideal position to give you relevant information on your disease and treatment as they know your individual circumstances. Cancerbackup has a help line (0808 800 1234) and a prize winning video available in English, Italian, Urdu, Bengali, Gujarati & Hindi explaining Radiotherapy & Chemotherapy. Cancernet.co.uk has over 500 pages describing cancer, its management, practical tips and tool which patients, their carers and their doctors have found helpful during the cancer journey.