'I’ve never smoked in my life, so how did I get lung cancer?'

It is well-known that smoking cigarettes is a major cause of lung cancer. According to the National Cancer Centre Singapore (NCCS), over 90 per cent of lung cancer is caused by cigarette smoking.

However, there have been more cases of lung cancer affecting people who have never smoked, and this has only increased over the years.

This Lung Cancer Awareness Month, Dr Hsieh Wen-Son, medical oncologist from Icon Cancer Centre, shares more about the disease and how advancements in treatment options are contributing to improved survival rates.

Lung cancer is the second-most common occurring cancer in men and third-most common cancer in females in Singapore, according to the National Registry of Diseases Office.

There are two main types of lung cancer - non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) - that differ in shape and size of the cells from which they arise.

According to the Singapore Cancer Society, SCLC makes up 10 to 15 per cent of all lung cancer cases. SCLC, as its name suggests, are very small cells that grow and spread to other organs more quickly than NSCLC.

While smoking is the number one risk factor for both SCLC and NSCLC, NSCLC has been found to occur increasingly more often in non-smokers. Dr Hsieh says that he has been seeing more cases of people in their 30s and 40s who have never smoked before getting NSCLC. However, the prognosis for NSCLC is better than SCLC.

The cure rate for stage 1 NSCLC is 70 to 80 per cent with surgery alone, while the cure rate for stage 1 SCLC is estimated to be about 25 to 30 per cent with surgery followed by concurrent chemoradiation," says Dr Hsieh.

According to Dr Hsieh, many non-smokers are in disbelief when they find out that they are diagnosed with lung cancer. "You have a lower risk because you do not smoke but it is still possible. For reasons we don't yet understand, we are seeing younger people who are non-smokers who have lung cancer," he adds.

Other than smoking, the causes of NSCLC are unknown, although there is evidence that environmental factors such as pollution and exposure to cancer-causing chemicals increases the risk of developing the disease.

It is also difficult to detect lung cancer as both SCLC and NSCLC have no symptoms in the early stages. Patients do not experience any symptoms until the cancer is in the later stages.

Even then, the symptoms, which include a persistent cough, chest pain and shortness of breath, are not specific to lung cancer.

This is why lung cancer is often diagnosed at an advanced stage - about 70 per cent of lung cancer is found at stage three or four, while 30 per cent is found in stage one or two, says Dr Hsieh.

However, he stresses that being diagnosed with lung cancer is not a "death sentence", which is a common misconception among many patients.

There are various treatment options that have seen some success in treating both types of lung cancers.

Chemotherapy and radiotherapy are typically used to treat SCLC, which responds well to treatment, although the cancer tends to grow back quickly, often within three months. NSCLC is also responsive to these treatments but grows back more slowly, explains Dr Hsieh.

He adds that patients undergoing chemotherapy are also able to live a better quality of life, thanks to more advanced chemotherapy drugs that are more effective and have less side effects. There are also advancements in supportive therapy to effectively help patients manage the common side effects of chemotherapy such as nausea and vomiting.

Targeted therapy can also be used to treat patients with NSCLC in instances where there are genetic changes that cause the cancer cells to grow and spread. Some known "driver mutations" include changes in EGFR, ALK and ROS-1.

A commonly used type of oral medication, known as tyrosine kinase inhibitors (TKI), block the over-active proteins that result from these genetic abnormalities. As these medications are specifically developed to target the cancer cell, they are highly effective in controlling the cancer in patients whose cancer cells carry these mutations without causing too many side effects, says Dr Hsieh.

Another type of targeted therapy that has made huge advances in the last decade is immunotherapy. Immunotherapy treatments stimulate the immune system to attack the tumour.

Patients generally receive drugs that stimulate T cells (a type of white blood cell) in the immune system to attack the tumour or drugs that block a protein called PD-L1.

According to the National Cancer Institute, PD-L1 is naturally found in the body and functions as a "brake" to prevent immune cells from attacking non harmful cells, healthy cells in the body. However, tumour cells can evade detection from the immune system by covering themselves in PD-L1.

This is where immunotherapy drugs come in. They 'unmask' the cancer cells, block these protein cells on the tumour surface, and 'reactivate' the body's own immune system to better recognise cancerous tumours and attack accordingly.

According to Dr Hsieh, immunotherapy has shown to increase survival rates in patients. A study presented at the European Society for Medical Oncology Virtual Congress 2020, showed that about 30 per cent of patients whose lung cancer expressed high levels of PDL1 who have undergone immunotherapy have a five-year survival rate - something that was unheard of five to six years ago. In addition, ten per cent of patients had complete disappearance of their cancer.

He is optimistic about advancements in treatments: "There's been much improvement in lung cancer treatments with more choices available. These can help better manage the condition, contribute to survival rate and improve the quality of life for lung cancer patients and their caregivers. Don't be afraid to get checked if you have symptoms such as a persistent cough."

November is Lung Cancer Awareness Month. Empower yourself with more information about lung cancer, and visit icanwewill.com.sg.

Dr Hsieh Wen-Son is specialised in the treatment of various types of cancers and is active in developing novel cancer diagnostics and molecularly targeted anti-cancer treatments. After studying Philosophy and Psychology at Oxford University on a Rhodes Scholarship, Dr Hsieh obtained his medical degree from Johns Hopkins University. After completion of his training in Internal Medicine at Duke University and in Medical Oncology at Johns Hopkins, Dr Hsieh was active in patient care, teaching, and research as a full time faculty member at the Johns Hopkins University School of Medicine with a primary appointment in the division of haematologic malignancies.