THE cancer patient's case was fairly typical: Surgery to remove the breast tumour, followed by chemotherapy.

But oncologist Wong Nan Soon of the National Cancer Centre Singapore (NCCS) did not also prescribe tamoxifen, the hormone treatment received by most breast cancer patients.

It cuts the risk of the cancer recurring by 20 per cent to 30 per cent, and costs only about $30 a month.

Dr Wong did not prescribe tamoxifen because a genetic test of the woman's tumour revealed that she would not respond to the treatment. It was pointless to put her through its side effects, such as hot flushes, fatigue and aching joints.Yet just a decade ago, women with breast cancer invariably had the same treatment regime: Surgery to remove the tumour, followed by chemotherapy and hormonal treatment to try and kill any residual cells missed by the knife.

Today, surgery remains the main option. But after the tumour has been removed, follow-up treatment is now targeted to the type of tumour.

This comes with the discovery of why some, but not others, react better to certain treatments.

Doctors now know that while three in four women have tumours that respond well to tamoxifen, there is a small number whose chances of survival drop when given the hormonal treatment.

Associate Professor Tan Puay Hoon, head of pathology at the Singapore General Hospital, said a simple test that costs $196 will identify who should not be given tamoxifen.

Today, all women in Singapore with breast cancer, the most common cancer among women, have their tumours genetically tested.

And targeted therapy has improved even more with a more expensive medicine called Herceptin. But it works for only about one in four women.

For such women, Herceptin, which costs $35,000 to $40,000 for a year's treatment, would halve the risk of the cancer recurring.

A person with Stage 2 cancer - a tumour that is 2cm to 5cm but has not yet spread to the lymph nodes - has a 30 per cent chance of the cancer recurring within 10 years. This drops to 15 per cent if Herceptin is used.

Dr Wong said that once cancer recurs, survival is slim as the cancer is difficult to get rid of and would likely have spread to other parts of the body.

Herceptin is not subsidised, but a $2 million donation from the Singapore Cancer Society has made it possible for 190 subsidised patients at the NCCS to receive the treatment this year.

With targeted treatment comes hope that the number of women who die of breast cancer will fall from the current 270 a year.

This has happened in the United States, which has been using targeted therapy for some time. Dr Wong thinks the cure rates here will follow the US pattern, where nine in 10 women survive.

Unfortunately, about 15 per cent of women do not benefit from either tamoxifen or Herceptin. There are other drugs, but it is not known yet what works best.

The NCCS will start a trial early next year to try and find out what these might be.

But Dr Wong said screening is still the most important way to beat the disease as it is best to catch and treat all cancers early.

salma@sph.com.sg