Personalised Medicine for Lung Cancer
On 19 September 2020, Mount Alvernia Hospital and Icon Cancer Centre jointly organised a livestreamed event, supported by Mundipharma Singapore. Our on-campus specialist Dr Shang Yeap spoke on the use of personalised medicine in the treatment of lung cancer, and the management of their side effects. Here are some of the highlights.
LUNG CANCER, ONE OF THE MOST COMMON CAUSE OF CANCER DEATHS
In the Q&A session on lung cancer, Dr Yeap confirmed that lung cancer is the second most common form of cancer among Singaporean males after colorectal cancer, and remains one of the most common cause of cancer-related deaths in Singapore. Though smoking is still the main cause of lung cancer, a worrying factor is the incidence of lung cancer among nonsmokers. Worldwide, about 20 percent of lung cancer patients have never smoked. In Singapore, that number is as high as 30 percent, which is even more disturbing.
Dr Yeap confirmed that genetics play a part in determining your risk of getting lung cancer, and pointed out that just being Asian alone puts you at a higher risk of getting lung cancer unrelated to smoking. It is possible that there is a genetic mutation in Asians that makes certain individuals more sensitive to lung carcinogens such as secondary smoke.
There are two main types of lung cancer – small cell and non-small cell lung cancer. Smokers have a higher chance of getting small cell lung cancer, which tends to be aggressive and resistant to treatment. Non-smokers, on the other hand, have a higher chance of getting non-small cell lung cancer, which is less aggressive and more responsive to treatment.
As there are no official screening programmes for lung cancer, it is often picked up at a later stage when it is less treatable. Many early-stage lung cancer patients with a 2cm or 3cm tumour have no symptoms at all. At a more advanced stage, common symptoms include a persistent cough, coughing up blood, difficulty breathing and chest pains.
How is lung cancer diagnosed?
Dr Yeap: While a chest X-ray may or may not pick up lung cancer, a CT scan or a CAT scan will provide a clearer picture, depending on its size. However, a conclusive diagnosis requires a biopsy or a bronchoscopy, whereby a tiny camera is inserted into the lung (similar to a colonoscopy).
Once lung cancer has been diagnosed, a PET scan can determine whether the cancer has spread to other parts of the body.
What are the common forms of treatment for lung cancer?
Dr Yeap: Treatment options for lung cancer are similar to those for breast cancer – namely surgery, radiation and chemotherapy (systemic treatment). Early-stage cancers are usually treated with surgery. Later stage cancers are more often treated with a combination of radiation and chemotherapy. Advanced cancers are often managed with chemotherapy, when a cure is unlikely.
How has personalised medicine improved outcomes for lung cancer patients?
Dr Yeap: Twenty years ago we only knew whether a lung cancer was a small cell or non-small cell type. In the last 15 years or so, we’ve drilled down to the molecular biology of lung cancer through genetic testing of the cancer itself (not the carrier, as for breast cancer). This determines the presence or absence of certain driver mutations that accelerate the progression of the cancer. One common driver mutation is the EGFR gene. Up to 60 percent of lung cancer patients have this driver mutation, which is highly treatable with personalised medicine. The good news is personalised medicine for lung cancers is usually administered in tablet form. Unlike chemotherapy, tablets do not affect other good cells and have far fewer side effects.
How effective is personalised medicine?
Dr Yeap: Twenty years ago we hit everyone with the same drugs. These days, personalised medicine targets cancer almost like a sniper aiming for a target. The most effective ones are fast-acting and can shrink cancers very quickly.
As mentioned, targeted therapy is usually given as tablets, and side effects are minimal. Though tablets can cause rashes and diarrhoea, they seldom cause nausea or hair loss. Many lung cancer patients are on tablets that can keep their cancer under control for many years.
How long can a stage IV patient, for example, carry on with ‘maintenance chemotherapy’?
Dr Yeap: A strong course of main chemotherapy can last for about a month, then the patient may be put on what we call ‘maintenance chemotherapy’ to keep the cancer under control for much longer. Two factors cause the cessation of maintenance chemotherapy. One is when the side effects erode quality of life. The second is when the maintenance chemotherapy simply ceases to be effective and fails to control the cancer. We generally continue maintenance chemotherapy until one of these factors arises.
What is immunotherapy and who is it suitable for?
Dr Yeap: Though it is not chemotherapy, immunotherapy is administered like chemotherapy via infusion. It essentially boosts your own immunity, and is particularly effective for patients whose cancers do not have driver mutations. Side effects are few and rare.
For patients with a high percentage of PD-L1, a protein that helps keep immune cells from attacking non-harmful cells in the body, immunotherapy alone can be adequate. For patients with lower PD-L1, immunotherapy tends to be more effective when combined with chemotherapy.
In short, genetic profiling is very important for developing a personalised treatment plan, and many biomarkers will be taken into consideration.
Are there any disadvantages associated with targeted therapy and immunotherapy?
Dr Yeap: There are few side effects except for one – the blow to your wallet. The big problem is the cost. Lung cancer treatment with targeted therapy or immunotherapy can easily amount to $10,000 or more per month. We are quite fortunate in Singapore, since most people can access these drugs through government subsidies and insurance.
What is the risk of getting lung cancer for second-hand smokers and ex-smokers?
Dr Yeap: We do know that second-hand smoking will increase your risk of getting lung cancer, though we cannot quantify it as a percentage. While the risk is obviously not as high as it is for first-hand smokers, the period of exposure can be longer. For example, children who grow up in households with smokers will have prolonged exposure. I advise patients who are exposed to second-hand smoke to firstly encourage the smokers to quit smoking, and secondly to ensure that the smokers understand that they are putting their family members at risk.
The good news is that upon quitting, your risk starts to drop and continues to drop with each passing year. At 15 years after quitting, your risk drops by up to 70 percent.
Other than smoking, what are other risk factors for lung cancer?
Dr Yeap: There is insufficient evidence to say that exposure to incense increases your risk, but exposure to certain chemicals such as asbestos and uranium certainly increase your risk.
CHECKLIST FOR LOWERING YOUR RISK OF BREAST CANCER
✓ Know your family’s medical history
✓ Exercise regularly (30 minutes, five times a week)
✓ Go for regular check-ups and screenings
✓ See a doctor if you have a cough that persists for more than a month, cough up blood, experience difficulty breathing or suffer chest pain
✓ Do not smoke
✓ Limit alcohol intake
✓ Follow a healthy balanced diet with plenty of fresh fruits and vegetables and a limited intake of processed foods and fatty meats
GLOSSARY
Personalised medicine – Any treatment that is customised to the individual patient
Maintenance therapy – The treatment of cancer with medication, typically following an initial round of treatment, which may include chemotherapy, hormonal therapy or targeted therapy
Immunotherapy – A type of cancer treatment that boosts the body’s natural defences or immune system to fight cancer
Hormone receptor-positive – Describes cancer cells that have a group of proteins that bind to a specific hormone such as oestrogen or progesterone
Highlights are taken from our FB Live, ‘Personalised Medicine for Cancer Care’ on 19 September 2020. Click here to watch the whole session.
This article is taken from our My Alvernia Magazine Issue #42/43. Click here to read the issue on our website or on Magzter.
