Bowel cancer: New treatments, improved prognosis

While bowel cancer (also known as colorectal cancer) remains one of the most deadly cancers, researchers are making steady progress against this disease. New medicines are helping people with even the most advanced metastatic disease (that is cancer that has spread to other parts of the body) to live longer. Admittedly, there's no cure, and the improvements - which can add several months to a patient's life - may seem modest.

However, for people living with advanced bowel cancer - and their loved ones - small improvements make a huge difference. Experts are confident that treatment will keep getting better.

"I think the attitude has changed among doctors, especially when it comes to metastatic colorectal cancer," says cancer specialist Dr Paulo Hoff. "We used to have a pessimistic view, but now we're seeing more patients with metastatic cancer responding to treatment. They are also responding well for a longer time."

"We have more tools than ever before to treat colorectal cancer," says bowel cancer specialist Dr Leonard Saltz. "What we're doing now is learning how to use them most effectively."

A turning point in treating bowel cancer

For decades medication for bowel cancer was limited to two medicines, 5- fluorouracil (5FU) and leucovorin. However, about 15 years ago, things began to change, with the approval of two new medicines:

• Irinotecan was introduced for people with metastatic bowel cancer that had recurred or spread beyond the colon.
• A few years later, oxaliplatin was approved for use in combination with 5-fluorouracil and leucovorin.

The new medicines improved survival to an extent. For example, one study published in the New England Journal of Medicine in 2004 found that adding oxaliplatin to standard chemotherapy (treatment that uses anticancer -cytotoxic - medicines to destroy cancer cells) boosted survival by 11% among patients with advanced disease.

Advances in targeted therapies for bowel cancer

Subsequently targeted therapies were introduced. Bevacizumab and cetuximab are monoclonal antibodies, a new generation of cancer medicines that can specifically target malignant tumours.

The problem with traditional chemotherapy is that it cannot be focused. The medicines go throughout the body, affecting both cancerous cells and healthy cells alike. Targeted therapies affect the specific mechanisms that allow cancer cells to grow. As a result, they may have fewer side effects.

Bevacizumab is modelled on the antibodies that naturally protect the body. It blocks the effects of a substance in the blood that helps tumours grow new blood vessels. This substance is called vascular endothelial growth factor (VEGF.) By preventing the creation of new blood vessels in the tumour, the cancer is starved of oxygen and nutrients. Cetuximab blocks the effects of a different growth factor called epidermal growth factor (EGF).

Studies have shown that these medicines do help. A 2004 article published in the New England Journal of Medicine found that bevacizumab, when combined with 5-fluorouracil and leucovorin and irinotecan for metastatic cancer, could increase life expectancy by about five months. Another 2004 article in the New England Journal of Medicine looked at people who were no longer responding to irinotecan. By adding cetuximab to irinotecan, the doctors were able to significantly slow down the progression of the disease, when compared with the use of cetuximab alone for treatment.

However, there are some drawbacks to these new medicines. For one, they are both only approved for certain cancer patients. They haven't yet been shown to work in earlier stages of the disease, and they are still associated with side effects. In addition, bevacizumab seems to increase the risk of heart attacks and strokes, which makes it unsafe for some people.