Breast cancer is the most common cancer among women worldwide. Each year about 1.4 million new cases of breast cancer are diagnosed worldwide, and over 450,000 women will die of the disease annually. Breast cancer is also the leading cause of cancer death among Thai women with more than 5,000 women dying from the disease each year.

Although it only affects 15 to 20 per cent of breast cancer patients, the HER2-positive type is one of the most aggressive as it causes cancer cells to reproduce uncontrollably.

On the brighter side, it is one of the cancers for which scientists have developed a targeted therapy known as trastuzumab that can prolong life and allow victims of the disease to enjoy more time with their families.

Developed by a team of scientists with Roche’s Genentech Company in the US, trastuzumab was approved by the US Food and Drug Administration for HER2-positive metastatic breast cancer in 1998 and is available as a treatment of choice in Thailand.

One of the Genentech team who worked on the drug Dr Mark Sliwkowski was recently on a visit to Bangkok and explained to oncologists and selected members of the press how it works.

The HER2 (Human Epidermal Growth Factor Receptor 2) proteins are receptors on breast cells. Normally, HER2 receptors help control how a healthy breast cell grows, divides, and repairs itself. Once it doesn’t work correctly, HER2 will copy of itself and make the breast cells grow and divide in an uncontrolled way. Sliwkowski and his team believed that the only way to stop this HER2 amplification was by using monoclonal antibodies – man-made copies of proteins that the body’s immune system creates to fight off bacteria and viruses in the hope that these antibodies would not only stop tumours from growing but also shrink them.

Using laboratory mice as their subjects, the team developed a mouse antibody that was later refined into to a humanised antibody that wouldn’t be rejected when injected into the human body.

There were several challenges along the way, not least because no previous work had been done on humanised antibodies. “As scientists and drug developers, we fail frequently, which I think is something people don’t appreciate. If your ego or personality can’t accept failure, you don’t learn from the failures. You can’t move on from the failure and so you are not going to be successful,” says Sliwkowski who has been working on the HER2 therapy for decades.

Trastuzumab was initially approved by the US FDA for use in the advanced stage of cancer but is now also used in early stage HER2-positive breast cancer.

Genetech has continued its research into treatments for the disease and has developed the second and third generation of trastuzumab for advance stage treatments. These are Pertuzumab and the latest TDM-1.

In Thailand, trastuzumab is used for early stage HER2-positive breast cancer after the patient has already received chemotherapy or surgery A trastuzumab injection is given every three weeks for 12 months and can prevent the cancer from returning.

However here, as in some other countries, price is a major factor. Each injection costs Bt40,000, which translates to more than Bt1 million for the entire treatment. Patients under the universal Bt30 healthcare scheme and social security are covered for the treatment.

However that cover is no longer applicable for treatment with Trastuzumab, Pertuzumab or |TDM-1 should the cancer return |at a later date.