Rituximab (MabThera)

Often described as the "magic bullet" of cancer treatments, Rituximab is used to treat several types of low-grade non-Hodgkin's lymphoma and is sometimes given by itself to people whose cancer has come back after chemotherapy. For some types of lymphoma it is the first treatment used and is given in combination with chemotherapy.

Belonging to a group of cancer drugs known as monoclonal antibodies, these antibodies are used to try and destroy some types of cancer cells while causing little harm to normal cells. Designed to recognise certain proteins that are found on the surface of some cancer cells, Rituximab locks onto a protein called CD20 which is found on the surface of one of the main types of normal white blood cells (B-cell lymphocytes).

It is also present on the surface of most of the abnormal B-cell lymphocytes which occur in most types of non-Hodgkin's lymphoma. Rituximab acts by attacking both abnormal (malignant) and normal B-cell lymphocytes. However, says CancerBACUP, the body quickly replaces any normal white blood cells which are damaged, so the risk of side effects from this is very small.

Trastuzumab (Herceptin)

Heralded as having "enormous implications for women with advanced breast cancer" by Delyth Morgan, the chief executive of Breakthrough Breast Cancer, this drug has also achieved notoriety for its availability having become subject to a national postcode lottery despite having received NICE approval as long ago as March 2002.

Trastuzumab is used to treat women whose breast cancer has come back or has metastasised (spread to other parts of the body). It also belongs to a group of cancer drugs called monoclonal antibodies.

Some breast cancer cells can be stimulated to divide and grow when a protein produced naturally in the body (human epidermal growth factor) attaches itself to another protein, which is found on the surface of breast cancer cells (HER2, sometimes called CerbB2).

Trastuzumab blocks this action by attaching itself to the HER2 protein so that the epidermal growth factor cannot reach the breast cancer cells. In doing so it stops the cells from dividing and growing. Trastuzumab also works by attracting the body's own immune cells to help destroy the cancer cells.

Unlike many cancer treatments, which attack all cells including healthy ones, Herceptin has fewer side-effects as it targets only cancer cells.

Currently it appears that only about one in five women with breast cancer have tumours that will be sensitive to trastuzumab. It only works in women who have increased amounts of the HER2 protein and appears to have little effect in other women.

Without treatment, HER2 positive women have an average life expectancy of less than one year.

Imatinib (Glivec)

"The day leukaemia patients have been waiting for," is how Dr Richard Sullivan of Cancer Research UK described the decision when Imatinib was finally given NICE approval in early 2002.

Imatinib is currently used for the treatment of patients with certain types of leukaemia (most commonly chronic myeloid leukaemia) and a rare type of stomach cancer known as gastro-intestinal stromal tumour (GIST).

It works by blocking signals within cancer cells and preventing a series of chemical reactions that cause the cell to grow and divide.

The growth of cells in the body is controlled by a group of chemicals called growth factors. These can attach themselves to special proteins on the surface of particular cells. This starts a series of chemical reactions within the cell which trigger it to grow and multiply. In people with chronic myeloid leukaemia (CML) white blood cells are produced which have a damaged receptor protein. This receptor sends out the "grow and divide" signal to the cells even when there is no growth factor present. This leads to an overproduction of immature white blood cells.

Imatinib identifies the faulty receptor and sticks to it, which prevents it from stimulating the cells to grow. Because it blocks the "grow" signal, Imatinib is known as a signal transductase inhibitor.

Anastrozole: the next big step toward prevention?

Cancer Research UK announced a major new trial in September which it heralded as embarking on "the next big step towards preventing breast cancer".

The drug involved in the trial, Anastrozole, is believed to reduce the risk of breast cancer in post-menopausal women by more than 50 per cent.

The 10-year study, IBIS-11 (or International Breast Cancer Intervention Study 11), will test the drug on 10,000 healthy women who are judged to be at an increased risk of the disease.

Anastrozole has already been shown to be the most effective hormone treatment for breast cancer and, with approximately 30,000 postmenopausal women diagnosed with breast cancer every year,

Cancer Research UK estimates that "if successful" intervention with the drug could mean several thousand fewer women developing the disease each year.

The trial follows the successful IBIS-1 study which demonstrated that tamoxifen reduced the incidence of breast cancer by a third in women at a higher risk of the disease. During trials of anastrozole as a treatment for early breast cancer, researchers observed that women taking the drug were around 40 per cent less likely to be diagnosed with a second cancer in the opposite breast compared to women taking tamoxifen.

Although both anastrozole and tamoxifen work by interfering with the production of oestrogen, Anastrozole actually stops the production of the hormone in postmenopausal women and appears to have fewer side-effects than tamoxifen. However anastrozole does not have the beneficial effects of tamoxifen on the bones, although Cancer Research UK says that this will be carefully monitored and managed within the trial.

"If the drug lives up to its promise," says Kate Law, Head of Clinical Trials at Cancer Research UK, "thousands of cancers could be prevented in the UK alone."