Biological therapies (targeted therapies) for rectal cancer
Biological therapies are anti-cancer medicines that work by affecting processes that occur within the cells.
This interferes with the cells’ ability to grow. There are several different types of biological therapies. The main ones used to treat rectal cancer are monoclonal antibodies. Monoclonal antibodies are drugs that recognise and lock onto specific proteins (receptors) present in particular cancer cells. Because of this they are often called targeted therapies, because they ‘target’ the cancer cells.
Some cancer cells have proteins called epidermal growth factor receptors (EGFRs). These are stimulated to grow and divide when other proteins in the body, known as growth factors, attach to the EGFR receptors. The monoclonal antibodies cetuximab (Erbitux®) and panitumumab (Vectibix®) lock onto the EGFR, stopping growth factors from attaching. This may prevent the cancer cells from growing and dividing.
Not all bowel cancers respond to cetuximab or panitumumab. Your doctors will test the cancer cells for a gene called KRAS. Knowing if the KRAS gene is normal or changed (mutated) can help the doctors decide whether cetuximab or panitumumab will be appropriate for you.
Cetuximab and panitumumab can be used to treat bowel cancers that have spread outside the bowel (advanced or metastatic cancer). Cetuximab is usually given in combination with chemotherapy, but it can also be used on its own. It’s given as a drip (infusion) into a vein. Panitumumab is usually given on its own as an infusion into a vein.
The National Institute for Health and Clinical Excellence (NICE) advises doctors about treatments available on the NHS. It has recommended the use of cetuximab in combination with chemotherapy for some people who have advanced (metastatic) bowel cancer that has spread to the liver, but can’t be removed with surgery.
This treatment may make it possible to remove the secondary cancer in the liver using surgery. Your cancer specialist can discuss with you whether cetuximab is recommended for you. Currently, panitumumab is not recommended by NICE.
Bevacizumab (Avastin®) is also a monoclonal antibody but it works in a slightly different way. It can also be used to treat advanced bowel cancers that have not been controlled by chemotherapy. It works by preventing the cancer from developing a blood supply, and so starves the cancer of oxygen and nutrients. Drugs that interfere with blood vessel growth in this way are called angiogenesis inhibitors or anti-angiogenics. Bevacizumab is currently not recommended by NICE and as a result it may not be possible to get it on the NHS. However, if you live in England, your doctor can apply for funding through the Cancer Drugs Fund so you may be able to have treatment with these drugs that are not available on the NHS.
Some people can have an allergic reaction to cetuximab. This can include a flu-like reaction, a drop in blood pressure or feeling sick (nausea). This is more likely to happen just after you have been given the drug. Some of the other possible side effects include skin rashes, diarrhoea, hair changes, sore eyes and breathlessness.
Bevacizumab can also cause an allergic reaction. Some of the other possible side effects are feeling sick (nausea) and being sick (vomiting), tiredness, diarrhoea, high blood pressure, a lowered resistance to infection and an increased risk of blood clots.
The first dose of cetuximab and bevacizumab is given slowly, over a number of hours. You may also be given drugs to make an allergic reaction less likely.