When Mr Wong was diagnosed with nose cancer in 2009, he thought it was the end for him.

The cancer was in advanced Stage 4, the worst phase, and the cancer cells had spread to his lungs and lymph nodes.

His doctor told him there was no way to completely get rid of the cancer.

But within weeks, he was thrown a lifeline. The 49-year-old was given the opportunity to take part in a clinical trial that uses immunotherapy to fight advanced nasopharyngeal or nose cancer.

This treatment uses a patient's own immune system to fight the cancer cells.

He won the battle and has been cancer-free for the past five years.

"I feel very blessed," said Mr Wong, who declined to give his full name. "Going for the trial was the last resort. Otherwise, it would just be waiting for death."

He was among 35 people who took part in the trial conducted by the National Cancer Centre Singapore (NCCS) in 2009.

He began his treatment with chemotherapy, receiving the first of four cycles in March 2009.

After the fourth cycle, he received the immunotherapy treatment in six cycles, the last of which was completed in March 2010.

Last month, the results were highlighted at the inaugural International Cancer Immunotherapy Conference held in New York, as an example of how immunotherapy can be used to successfully treat some cancers.

The effort was commended by one of the world's top cancer and immunology experts, Professor Helen Heslop, from the Baylor College of Medicine, Texas, US.

While Mr Wong's case was an "outlier", Dr Toh Han Chong, deputy director of NCCS and a senior consultant at its division of medical oncology, said the results were promising, with the median overall life survival at 30 months instead of 12 to 18 months.

"Every time we see a patient like Mr Wong with nose cancer that has spread to distant sites, we have to tell them realistically that they are not curable," Dr Toh said.

"He has remained cancer-free for over five years. That is extremely rewarding because most people die from this disease."

The team is now conducting a phase 3 trial for advanced nose cancer, the first to be undertaken in the world.

More than 300 patients will be recruited for it and they will come from Singapore as well as countries like Malaysia and the US.

In recent years, immunotherapy has been hailed as a cancer treatment which gives rise to "super survivors" or patients who outlive their expected years.

There are different forms of it and, in Mr Wong's case, his own body's T-cells, a type of white blood cell, were used to attack the cancer cells.

These T-cells were trained to recognise only the Epstein-Barr Virus (EBV) protein found on the surface of the nose-cancer cells.

The EBV proteins are the culprits that trigger the development of nose cancer.

Once the T-cells grow to about one billion, they are put back into the patient.

Many studies have shown that the cells can potentially continue to grow to 1,000 times their original number and stay in the body for as long as 10 years, said Dr Toh.

As they would target just the EBV proteins found on the surface of nose-cancer cells, the body can more effectively destroy them.

The side effects of immunotherapy vary among different cancers, but for nose cancer these were not significant, Dr Toh said.

However, immunotherapy is not a substitute for other forms of cancer treatment such as chemotherapy or surgery, he emphasised.

Rather, it is an "additional weapon" in the war on cancer.

"The results of the trial are encouraging but you need everything - chemotherapy to shrink the cancer before you hit it hard with immunotherapy," he said.