Have you ever known that lung cancers come in different “sizes”? The common form of lung cancer most patients suffer from is the “large” variety, or in medical lingo, the “non-small cell” type. It would be easy to deduce, therefore, that there has to be a “small” variety, or, “small cell” type of lung cancer.

Mr. L, a gentleman in his late 60s, listened attentively and tried his best in take in the information as I explained that he had the less common small cell type of lung cancer.

“Small” versus “non-small”. Which is worse?

In this case, the “small” one actually packs a bigger punch. Small-cell lung cancer is generally more fatal.

If there ever were an Olympic Games pitting various types of cancer against one another in a competition of speed of growth, small-cell lung cancer would no doubt be a medalist. It has one of the shortest doubling time of about 80 days – time taken to double the number of cancer cells in the body – in the world of cancers. Non-small cell lung cancer typically takes around 200 days to achieve the same feat.

Most cases – around 70 percent - of small cell lung cancers are discovered only when the disease is in the advanced stage. Even in the less common scenario of patients being fortunate to have their disease diagnosed in the early stage, less than 20 percent can be permanently cured. In the advanced stage, the situation is much grimmer; these patients typically live for only 2 months without treatment. Even with the use of chemotherapy, only about a third of patients with advanced small cell lung cancer will live to see another year.

It has oft been said that not all cases of lung cancer are associated with smoking; non-smokers, too, may develop lung cancer. Not so for small cell lung cancers. Of all patients of small cell lung cancer diagnosed every year, less than 3 percent are non-smokers. Small cell lung cancer is an almost exclusively smokers’ cancer.

Given the grim outlook of small cell lung cancer, it is perhaps a blessing that small cell cancer is not very common, forming about 15 percent of all cases of lung cancer worldwide. In Singapore, the percentage is somewhat lower at about 8 percent.

But such statistics would be cold comfort for Mr. L as he faced the diagnosis of small cell lung cancer.

Mr. L underwent a specialized scan – positron-emission tomography (PET-CT) – that confirmed his worst fears: his condition of small cell lung cancer was in the advanced stage.

Had Mr. L been diagnosed with the same condition last year instead of this year, the standard treatment would have been chemotherapy with the relatively poor treatment results I alluded to. Such treatment has been the standard for more than 2 decades. While the treatment of most types of cancer have improved by leaps and bounds over the last 20 years, the treatment results of small cell lung cancer hardly budged.

Thankfully, in March and August 2020, the Health Sciences Authority of Singapore (HSA) has given the green light for two forms of immunotherapy to be used for the treatment of advanced small cell lung cancer. The addition of immunotherapy to standard chemotherapy improved the odds of patients going past the next 1 year and beyond, from round about one third to more than half.

Mr. L listened intently as I explained the scientific concept of how cancers cells in the body survive by evading attack by the body’s immune system.

Cancer cells behave like wolves in sheep’s clothing and the immune system fails to recognize them as wolves. The scientific term for this “sheep’s clothing” is PD-L1. Cancer immunotherapy utilizes artificial antibodies, known as anti-PDL1 antibodies, to strip the sheep’s clothing off the back of the cancer cells. These antibodies are infused into the patient’s body at regular intervals of about 3 weeks. Deprived of their camouflage, cancer cells become exposed to attack by the body’s immune system.

Mr. L started on his fight against cancer with a sense of hope.

After a wait of 20 years, a new dawn in the treatment of advanced small cell lung cancer has arrived. It gives me comfort today to be able to offer patients battling such a difficult disease a better treatment. And yet, a doctor’s and a researcher’s work is never done. The search for a yet better treatment for small cell lung cancer continues.

My greatest hope is… the next major breakthrough will not be another 20 years in the making.

Dr Wong Seng Weng
Medical Director & Consultant Medical Oncologist of The Cancer Centre (Singapore Medical Group)
Member of the Singapore Cancer Society Lung Cancer Awareness Month Committee